Full Text Molecular Biology

Journal of Molecular Biology and Drug Design

 

Angiotensin-Converting Enzyme 2: Structure, Functions And Therapeutic Relevance In Several Pathophysiological Disorders To COVID-19

Satya Prakash Gupta*

Fellow, The National Academy of Sciences, 5, Lajpatrai Road, Prayagraj-211002, India.

*Corresponding Author: Gupta SP, Fellow, The National Academy of Sciences, 5, Lajpatrai Road, Prayagraj-211002, India. E-mail:  spgbits@gmail.com.

Citation: Gupta SP. Angiotensin-converting Enzyme 2: Structure, Functions and Therapeutic Relevance in Several Pathophysiological Disorders to COVID-19. Journal of Molecular Biology and Drug Design. 2021;1(1):1-22.

 

Copyright: © 2021 Gupta SP. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Received On: 1st February,2021     Accepted On: 23rd February,2021    Published On: 6th March,2021

Abstract

The article presents an account of various pathophysiological roles of angiotensin-converting enzyme 2 (ACE2), an enzyme that has been identified as a fundamental regulator of the renin-angiotensin system (RAS) in humans and is an important target in regulation of blood pressure homeostasis. The article first discusses its crystal structures in native and inhibitor-bound states.  ACE2 has gained a great therapeutic relevance and interest because of its ability to produce heptapeptide angiotensin (1-7) [Ang (1–7)] via two alternative pathways in concert with ACE.  It is predominantly expressed in the heart, kidneys and testes, and at lower levels in a wide variety of tissues, particularly the colon and lung and thus implicated in various diseases. The article also highlights the studies on its crucial role in the spread of the early born disastrous disease COVID-19.

Keywords: Angiotensin-converting enzyme 2, COVID-19, renin-angiotensin system, SARS-CoV-2, motif, crystal structure.

Introduction

The early born pandemic COVID-19 not only created the turmoil in the scientific world to go into the detail of its causative agent, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), but also created the interest to revisit the role of an enzyme called angiotensin-converting enzyme 2 (ACE2), found to play the crucial role in the life cycle of this virus.  ACE2 is a human homologue of angiotensin-converting enzyme (ACE), an enzyme that has been identified as a fundamental regulator of the renin-angiotensin system (RAS) in humans and is an important target in regulation of blood pressure homeostasis. RAS is one of the best-characterized hormonal systems, reflecting its central role in the control of blood pressure. ACE2 is a type I integral membrane protein which functions as a carboxypeptidase, cleaving a single hydrophobic/basic residue from the C-terminus of its substrates. It efficiently hydrolyses the potent vasoconstrictor angiotensin II (Ang II) to a heptapeptide angiotensin (1–7) [Ang (1-7)] and thus plays an important role in RAS. ACE2 has gained a great therapeutic relevance and interest because of its ability to produce Ang (1–7) via two alternative pathways in concert with ACE.  ACE2 is predominantly expressed in the heart, kidneys and testes, and at lower levels in a wide variety of tissues, particularly the colon and lung and thus implicated in various diseases. A review by Wiese et al. nicely describes its various physiological functions in RAS system as well as its roles in the pathophysiology of various diseases [1]. Now the interest for further research on different physiological roles of this enzyme and their implications in various diseases has arisen due to the elucidation of its crystal structure [2] as well as of a few other enzymes orthologous to it [3,4]. So, let us first discuss the structure of ACE2.

Structure of ACE2

The first crystal structures of the extracellular metallopeptidase domain of ACE2 in its native and inhibitor-bound states were reported by Towler et al. [2]. These authors then discussed the influence of these structures in understanding the substrate specificity and catalytic mechanism of the enzyme. However, before this study of Towler et al., two reports on the crystal structures of testicular ACE (tACE) and Drosophila ACE had already appeared [3, 4]. Towler et al. determined the 3D structure of the extracellular region of native ACE2 by multiple isomorphous replacement with anomalous scattering which was then refined to a crystallographic R-factor of 23.5% (Rfree = 28.7%) at 2.2-Å resolution. The extracellular region of the human ACE2 enzyme is composed of two domains: (1) zinc metallopeptidase domain (residues 19–611), which is around 42% identical to the corresponding domains of human somatic ACE (sACE) and tACE and (2) the domain located at the C terminus (residues 612–740) which is around 48% identical to human collectrin, a collecting duct-specific transmembrane glycoprotein that is a novel homolog of ACE2 and is developmentally regulated in embryonic kidneys [5]. The metallopeptidase domain of ACE2 can be further divided into two subdomains (I and II), which form two sides of a long and deep cleft Figure 1. The proteolytic active site of ACE2, which is a common structural feature of proteases and exists to avoid hydrolysis of correctly folded and functional proteins [6, 7], is deeply recessed and shielded. This proteolytic active site of ACE2 is also consistent with the profiles of binding of tethered inhibitors to sACE [8, 9].

Figure 1. Ribbon diagram of native ACE2 showing the secondary structure and also the two subdomains (I and II) that form the two sides of the active site cleft. Domain I (red), composed of residues 19–102, 290–397 and 417–430, is N terminus- and zinc-containing subdomain and domain II (blue), composed of residues 103–289, 398–416 and 431–615, is C terminus domain. The yellow sphere shows the active site zinc ion and the green sphere indicates the chloride ion. Reprinted from Ref [2]. Open Access publication

            In the subdomain I of ACE2, the zinc-binding site is located near the bottom and on one side of the large active site cleft, where in the native structure the zinc is coordinated with His374, His378, Glu402, and one water molecule. In subdomain II in native ACE2, a Clˉ ion is coordinated with Arg169, Trp477, and Lys481. When the binding of an inhibitor, MLN-4760 Figure 2A, with ACE2 was studied, it was found that both subdomains of ACE2 were nearly equally involved in binding with this compound. The study also revealed the important residues of ACE2 that could be involved in the binding with this inhibitor. These residues are shown in Figure 2. The inhibitor MLN-4760 has two carboxylate groups, one of which binds to the zinc atom by displacing the bound water molecule present in the native ACE2 structure. The zinc coordination sphere is constituted of H374, H378, and E402, i.e., His374, His378, and Glu402, residues. These three residues belong to the subset of 21 residues of ACE2 that are located within 4.5 Å of the bound inhibitor and make up the greater part of the active site. The terminal carboxylate of the inhibitor is H-bonded to the side chains of H345, H505, and R273, i.e., His345, His505, and Arg273. The secondary amine group of the inhibitor is also H-bonded to H345, P346, and E375, i.e., His345, Pro346, and Glu346 residues. Another H-bonding is between the residue T371 (Thr371) and one of the nitrogen atoms of imidazole ring of the MLN-4760. The one of the oxygen atoms of zinc-bound carboxylate group of the inhibitor is H-bonded to the phenolic group of Y515 (Tyr515) and the other oxygen atom of it is H-bonded to E375 (Glu375) of the enzyme. In addition to these potential H-bonding contributing residues, there are 11 more residues of ACE2 that make close contacts (<4.5 Å) with MLN-4760, which do not contribute direct H-bonding interactions but provide important electrostatic and van der Waals interactions with the inhibitor. These residues, in fact, refer to the S1 and S1′ peptide-binding subsites and thus provide binding specificity to the inhibitor as well as the substrate [2].

     Of the two peptide-binding subsites S1 and S1′, the S1′ is much larger than the S1 and is formed by the lengthwise channel between the two subdomains. Because of the large size of S1′ subsite, the 3,5-dichlorobenzylimidazole group of MLN-4760 is easily accommodated Figure 2. This indicates that large hydrophobic or basic residues, such as Arg and Lys, can be preferred at the P1′ position of peptide substrates [10]. Likewise, the smaller subsite S1 nicely packs the isobutyl group of MLN-4760, suggesting a similar preferred fit for a leucyl side chain at the P1 position of peptide substrates. These structural aspects of ACE2 have very much similarity to those of four proteins in the Protein Data Bank [11], namely: (1) recently solved human tACE (Code: 1O86) [3], an enzyme of the M2 metallopeptidase family, (2) Drosophila ACE (Code: 1J36) [12], (3) rat neurolysin (Code: 1I1I) [13], an M3 metallopeptidase family member, and (4) Pyrococcus furiosus carboxypeptidase (Code: 1KA2) [14], a member of the M32 carboxypeptidase family.

 

     (A) MLN-4760

 

Figure 2. A, structure of an ACE2 inhibitor, MLN-4760. B, schematic diagram showing binding interactions of the inhibitor MLN-4760 at the active site of ACE2. Residues shown in red belong to subdomain I and those shown in blue belong to subdomain II. Equivalent residues in tACE are in given in parentheses. Reprinted from ref [2]. Open Access publication

        ACE2 is a homologue of ACE. Therefore, a model of the active site of ACE2 based on the crystal structure of tACE was developed to find that the catalytic mechanism of ACE2 resembles that of ACE. However, there exist differences in substrate-specificity of the two, due to the existence of differences between the active site of ACE (dipeptidyl carboxypeptidase) and ACE2 (carboxypeptidase) [3]. The main differences occur in the ligand-binding pockets, particularly at the S2′ subsite and in the binding of the peptide carboxy-terminus and this is the reason that classical ACE inhibitor lisinopril Figure 3 is unable to bind to ACE2. In a study on sequence alignment of ACE2 with tACE, Guy et al. [15] had found that critical active site residues in ACE are conserved in ACE2. The two enzymes share many common features including the conservation of residues involved in catalysis Figure 4. Further, as with ACE, the activity of ACE2 is also dependent on chloride ions and is substrate-specific. However, while in the presence of chloride ions, ACE generates high levels of angiotensin II, hydrolysis of angiotensin II by ACE2 is inhibited. Whatsoever, according to Guy et al. [15], the mechanism underlying the substrate dependent manner of chloride activation/inhibition observed for both ACE and ACE2 remains unclear. Nonetheless, the chloride dependence of ACE has long been recognized [16] and the locations of two buried chloride ions were revealed in the structure of tACE [9]. At both the locations, an arginine residue was found to be essential for chloride activation and the sequence alignment of ACE2 with ACE revealed that at both the locations, CL1 and CL2, the arginine residues, Arg169 and Arg514, respectively, were conserved in ACE2. However, in the study of Towler et al. [2], a bound chloride in CL2 site was found to be intriguingly absent, which led to suggest that, unlike in ACE, this second site in ACE2 does not exist and therefore does not contribute to the chloride effect. It could there be assumed that it is actually the CL1 site that is responsible for chloride activation of ACE2. In later communication, Guy et al. [17] also noted the difference in chloride sensitivity between ACE2 and ACE and attributed this difference to the fact that ACE2 has only one chloride-binding site (CL1), whereas ACE has two sites (one in each subdomain). According to some other authors [18], there was a dramatic loss of chloride activation in the C-domain of ACE where the CL2 site was abolished. According to Towler et al. [2], the absence of CL2 site in ACE2 was due to the substitution of Glu398 and Ser511 in ACE2 for Pro407 and Pro519 in ACE.

 

Structural formula of lisinopril

Figure 3. Structure of classical ACE inhibitor, lisinopril

Figure 4: Model of ACE2 showing its active site and its residues (in black) coordinating the zinc ion. The equivalent residues in tACE are shown underneath (in red) with only one difference that in place of Glu406 in ACE2, there is Asp415 in tACE. Reprinted with permission from Ref [15]. Copyright 2003 American Chemical Society.      

      Both the enzymes, ACE and ACE2, are at the heart of many human physiological processes and contain a characteristic HEXXH motif (where X is any amino acid) that coordinates a catalytic zinc ion and as such are members of the M2 gluzincin family of metalloproteases. ACE is well-known for its role in blood pressure regulation via renin–angiotensin aldosterone system (RAAS), but plays important roles in fertility, immunity, haematopoiesis and diseases such as obesity, fibrosis and Alzheimer’s dementia. Likewise, ACE2 is also involved in many physiological processes and gained increasing therapeutic relevance and interest due to its ability to produce Ang (1–7) via two alternative pathways. As of now, it is implicated in cardiac dysfunction, hypertension [19, 20], heart failure, ventricular remodelling [21, 22], diabetes [23], Ang (1–7) regulation during pregnancy [30, 24], and above all as a functional receptor to the coronaviruses that cause severe acute respiratory syndrome (SARS) [25]. ACE2 is expressed in most human tissues and its expression levels are highest in the small intestine, testis, kidneys, heart, thyroid and adipose tissue. However, its expression levels are only intermediate in the lungs, colon, liver, bladder and adrenal glands and lowest in the blood, spleen, bone marrow, brain, blood vessels and muscle [26]. The elucidation of its crystal structure has created further interest to study more and more about the biochemistry and physiological role of this enzyme. According to a review by Lubbe et al. [27], both ACE and ACE2 cleave a variety of substrates in addition to their most well-known substrates: Ang I (ACE), Ang II (ACE2) and bradykinin (ACE), and are even capable of cleaving much longer substrates, e.g., ACE can cleave amyloid-ß peptides and ACE2 apelin-36, both of which are over 35 residues in length [28-30]. However, it is unclear how such longer substrates could be accommodated and cleaved by the domains of these enzymes. Although some attempts have been made in this direction [31], it is yet to be confirmed. For the mechanism of the catalysis of hydrolysis of peptide substrates, the hinge-bending motion of both ACE and ACE2 are crucial, where the movement of the two subdomains bring the catalytic components of the active site into a functional orientation [27].

Physiological and Pathophysiological Roles of ACE2 in the Body

       ACE2 has been found to be attached to the membranes of the cells of many crucial organs of the body, such as lungs, arteries, heart, kidney, and intestines [32, 33]. As already mentioned, ACE2 lowers the blood pressure by catalysing the hydrolysis of Ang II to Ang (1-7), a vasodilator [33-35]. In fact, it counters the activity of the related ACE by reducing the amount of Ang II and increasing that of Ang (1-7) [36]. Thus, it has been recognized as promising drug target for treating cardiovascular diseases [36, 37]. ACE2 differs from ACE in that only a single ACE2 protein species appears to be formed [38]. As compared to ACE, ACE2 is less widely distributed in the body and differs from ACE in its substrate specificity, functioning exclusively as a carboxypeptidase rather than a peptidyl dipeptidase [39]. Now let us describe the roles of ACE2 in different diseases.

Kidney Disease and Hypertension

ACE2 is the only known enzymatically active homologue of ACE in the human genome, which was initially found in heart, kidney, and testis with lesser amounts in colon, small intestine, and ovary [40]. However, it has also been found in the lungs, where it plays an important role in Ang- II metabolism [41, 42]. ACE2-mediated degradation of Ang II to Ang (1–7) has been shown in studies using kidney cortex preparations or isolated proximal tubules [43-45]. Abundant expression of ACE2 has been shown in kidney cortex, where its activity is higher than in heart tissue [46]. In the context of negative regulation of the RAS, ACE2 has been found to be a protective molecule against kidney diseases [47, 48]. In their review on ACE2 and kidney [48], Soler et al. had pointed out that some experiments on mice had led to conclude that a decrease in ACE2 may be involved in diabetic kidney disease, possibly by disrupting the metabolism of angiotensin peptides in such a way that Ang II degradation within the glomerulus may be diminished. However, under physiological conditions, ACE2 expression was found to widely vary within tissues and species [49]. According to Ye et al. [50, 51], it was found to be highly expressed in mouse kidney and then it was also noted that in human kidneys the pattern of its expression was similar to that of mouse kidneys [51, 52]. On the basis of different studies, Soler et al. [48] have concluded that a decrease in ACE2 may be involved in diabetic kidney disease, possibly by disrupting the metabolism of angiotensin peptides in such a way that Ang II degradation within the glomerulus may be diminished.

           Regarding hypertension, it is well known that the RAS is an excellent regulator of hypertension, where ACE2 promotes vasodilation by degrading Ang II and generating the vasodilators Ang (1-7) [53]. Thus, increasing the expression of ACE2 protects against increased blood pressure. It is thus natural that the inhibition of ACE2 may lead to promote essential hypertension (EH) [54]. Some genetic studies have identified polymorphisms in ACE2 as risk factors for EH in multiple populations, such as the Han-Chinese and Caucasian population [55, 56]. In a study, however, it has been found that aberrant methylation of the ACE2 promoter may be associated with EH risk [57].

Lung Diseases

Lung diseases include pulmonary hypertension (PH), pulmonary fibrosis (PF), and acute lung injury (ALI). Pulmonary hypertension is a type of high blood pressure that affects the arteries in your lungs and the right side of your heart, while pulmonary fibrosis is a lung disease that occurs when lung tissue becomes damaged and scared. Acute lung injury is associated to lung inflammation that develops in response to a variety of both pulmonary and generalized acute diseases. The most severe form of acute lung injury is acute respiratory distress syndrome (ARDS) that affects approximately one million individuals worldwide per year with a mortality rate of at least 30–50% [58, 59]. It is characterized by pulmonary oedema, accumulation of inflammatory cells and severe hypoxia [58, 59]. These lung diseases have gained further importance and come into the limelight since the identification of ACE2 as a severe acute respiratory syndrome (SARS) coronavirus receptor. The RAS has been implicated in the pathogenesis of these lung diseases, where ACE2 is supposed to protect against these diseases [60]. Regarding pulmonary hypertension, several studies have demonstrated that the exogenous expression of ACE2 or Ang (1–7) blocks experimental pulmonary hypertension by suppressing Ang II-induced inflammation and oxidative stress [61, 62]. Additional mechanisms by which ACE2 plays a protective role in pulmonary hypertension have also been studied, e.g., in an in vivo study, it has been found that overexpression of ACE2 in the lung inhibited pulmonary blood vessel wall thickening and muscularization of blood vessel [63], and in another study, it was found that attenuated ACE2 activity is associated with hyper proliferation and enhanced migration of pulmonary smooth muscle cells [64]. Thus, the use of ACE2 activator in treating pulmonary hypertension has been proposed [65, 66]. A detail of specific roles of ACE2 in lung diseases can be found a review by Jia [67].

      Pulmonary fibrosis (PF), a progressive lung disorder, with high morbidity and mortality is secondary to ALI/ARDS. The PF actually means scarring in the lungs that can destroy the normal lung and make it hard for oxygen to get into your blood. This PF can be idiopathic in some cases, that is a disease whose cause may not be known. An IPF (idiopathic pulmonary disease) may lead to respiratory failure with right heart dysfunction and death. ACE2 expression and activity are decreased in humans with IPF and in animal models of lung fibrosis [68-70]. Otherwise, ACE2 protects lungs by both degrading local Ang II and production of Ang (1–7) which shifts RAS balance towards the anti-inflammatory, antifibrotic actions via the ACE2-Ang (1–7)-Mas axis [71]. Mas is a G protein-coupled receptor, which acts as a functional receptor for Ang (1–7) [72] and which in addition to ACE2 and Ang (1–7) composes the vasodilator/antiproliferative arm of the RAS.

Cardiovascular Disease

It has been established that heptapeptide Ang (1–7) is an endogenous counterregulatory member of the RAS in the cardiovascular system and its counter-regulatory role has been legitimized by the discovery of ACE2. The ACE2 was initially supposed to be associated with only heart, kidney, and testes, but now its distribution in a wide variety of cardiovascular tissues has been well established [73]. Its role in cardiovascular homeostasis has been found to be quite critical and its altered expression to be associated with major cardiac and vascular pathophysiologies [73]. There is a general agreement that deletion of ACE2 results in significant alterations in cardiac and vascular functions. Cardiac tissues of patients with ischemic heart failure and patients with either idiopathic dilated cardiomyopathy or primary pulmonary hypertension have been found to have increased levels of ACE2 [74, 75]. These observations led to suggest that decrease in ACE2 is associated to impaired cardiac function and thus it can be assumed that excess of ACE2 would be protective to hypertension-induced cardiac dysfunction. Several such observations have supported principle that ACE2-Ang (1–7)-Mas axis is a physiologically relevant arm of the RAS and the relevance of this axis is further highlighted by its altered expression in many cardiovascular pathophysiologies, including hypertension, renal damage, heart failure, and vascular remodelling and thus it presents a new target for innovative therapeutic strategy for cardiovascular disease.

Cardiopulmonary Diseases    

The word ‘cardiopulmonary’ is combination of two words, cardio and pulmonary, and thus cardiopulmonary diseases refer to a range of diseases and conditions that affect the heart (cardio) and lungs (pulmonary). These diseases are serious and should not be taken lightly. There are two common types of cardiopulmonary disease, cardiovascular disease and chronic obstructive pulmonary disorder (COPD). The cardiovascular disease, should not be taken to refer to exactly heart disease, but to the conditions that involve blocked blood vessels and that can lead to a stroke or heart attack. On the other hand, COPD refers to a chronic inflammatory lung disease that results in the obstruction of airflow through the lungs.

         The RAS (renin-angiotensin system), in fact, has, as shown in Figure 5, two opposing arms, one represented as ACE-Ang II-AT1R and the other as ACE2-Ang-(1–7)-MasR [76].  In this, the first one is known as deleterious (or vasodeleterious) axis and the second one as beneficial or vasoprotective) axis. Both together in a balanced condition play crucial role in the maintenance of cardiopulmonary homeostasis, otherwise upregulation of the vasodeleterious axis leads to vasoconstriction, hypertrophy, inflammation, and cardiac remodelling [77], and stimulation of the vasoprotective axis leads to valuable cardiopulmonary effects [76], which may be either genetic overexpression [78-80], peptide infusion [81], or administration of synthetic molecules [82]. In a review, Cole-Jeffrey et el. [76] have presented evidence of the direct and indirect actions of ACE2 on the cardiopulmonary system. The reduction in Ang II and subsequent elevation in Ang (1–7) levels, which are actually brought out by ACE2, are supposed to have beneficial effects on the heart, lungs, brain, and progenitor cells. ACE2-mediated effects on cardiac and pulmonary tissues include vasodilation, anti-hypertrophy, anti-proliferation, and anti-fibrosis; and certain physiological functions, which promote cardiopulmonary health (such as endothelial function), facilitate angiogenesis, and enhance progenitor cell function, have been shown to be improved by ACE2 treatment [83-86]. ACE2 exerts favourable actions on the bone marrow (BM), which may lead to aid regeneration of the injured cardiopulmonary tissue through the improvement in the migratory potential of stem/progenitor cells [76]. The review by Sharma et al. [71] has also pointed out similar beneficial effect of ACE2 on cardiopulmonary diseases, addressing that cardiopulmonary diseases are associated with decrease in ACE2 activity and the reduction of these diseases with the increase in its activity.  

Figure 5: A schematic representation of two arms of RAS system: vasodeleterious arm (ACE-Ang II-AT1R) and vasoprotective arm (ACE2-Ang-(1–7)-MasR). MasR refers to Mas receptor. Reprinted from ref [76]. Open Access publication

COVID-19

ACE2 was extensively studied in the early 2000’s because of its binding to spike (S) protein of coronaviruses, SARS-CoV (severe acute respiratory syndrome coronavirus) and HCoV-NL3 (human coronavirus-NL3). Now it came to further limelight because of the outbreak of another deadly coronavirus SARS-CoV-2 (formerly 2019-nCoV), as this virus was also found to use ACE2 for its host cell entry. It was then extensively studied to find the ways to block the interaction between the S protein and ACE2, so that the SARS-CoV-2 infection can be prevented and the disease created by it, the so named as COVID-19, can be treated. Although, there is close evolutionary relationship between SARS-CoV-2 and SARS-CoV, the receptor-binding domain of SARS-CoV-2 differs in several key amino acid residues [87, 88], because of which it gains stronger binding affinity with the human ACE2 receptor and becomes more pathogenic. Since the ACE2 system is a critical protective pathway against many diseases related to heart, lungs, kidney, etc., as discussed in preceding sections, high binding affinity of SARS-CoV-2 with ACE2 has become disastrous. Thus, theoretically, both SARS-CoV-2 and ACE2 could be the target for therapeutic intervention.

      As shown in Figure 6, the virus SARS-CoV-2 has on its surface glycoproteins, called spike (S) proteins, that form trimers protruding from the viral surface Figure 6a. Each S protein is comprised of two functional subunits S1 and S2 [89], where the former mediates the receptor binding, after which the latter mediates viral membrane fusion using a highly conserved peptide [90, 91]. The S1 subunit has receptor binding domain (RBD) that mediates the binding to the host cell receptor Figure 6b. The initial attachment of SARS-CoV-2 to cells involves specific binding between its S glycoprotein and the cellular receptor ACE2 Figure 6c. This observation was based on a study by Yang et al. [92] using atomic force microscopy (AFM), where the interactions are monitored on model surfaces, in which the ACE2 receptor is attached to a surface and the S1 subunit or the RBD onto the AFM tip and on A549 living cells expressing or not fluorescently labelled ACE2. In a communication, Zhou et al. [93] reported that SARS-CoV-2 can enter only that cells which express ACE2 and not any other cells. It cannot enter cells which do not have ACE2 or that express other coronavirus receptors, such as aminopeptidase N and dipeptidyl peptidase 4 (DPP4). This confirms that ACE2 is essential for SARS-CoV-2 entry. Thus, SARS-CoV-2 has revived the importance of ACE2 and created further interest in the study on it.

          However, ACE2 is expressed in nearly all human organs in varying degrees but lungs have been found to be the primary target of SARS-CoV-2 [94, 95]. In a review, Ni et al. [96] have pointed out that other human cells also, such as myocardial cells, proximal tubule cells of the kidney, and bladder urothelial cells, highly express ACE2 and that it is abundantly expressed on the enterocytes of the small intestine, especially in the ileum [94, 95, 97]. Thus, through blood circulation the cell free and macrophage phagocytosis-associated virus may spread from the lungs to other organs with high ACE2 Figure 7.

       However, ACE2-related studies increased after the discovery of its crucial role in the spread of SARS-CoV-2. Now specific attentions have been diverted to find ACE2 inhibitors that may inhibit SARS-CoV-2 infection, but so far, no breakthrough has been achieved in this direction.  Among the rare ones, a study in this direction by Terali et al. [98] led to report a small set of promising repositionable drug candidates that have potential to interact with human ACE2, making it unrecognizable by SARS-CoV-2. The structures of these compounds are given in Figure 8 and their original biological activity and the binding energy of each with ACE2 are given in Table 1. The binding energy of all these compounds with ACE2 is greater than that of classical inhibitor of ACE2 (MLN-4760), _309.93 kcal/mol as reported by these authors.

figure1

 

Figure 6. A schematic diagram showing the binding of SARS-CoV-2 to the ACE2 host receptor.

(a) Schematic of a SARS-CoV-2 particle, an enveloped ssRNA (single-stranded RNA) virus expressing at its surface the spike glycoprotein (S), (b) exhibiting a complex between RBD of S1 and ACE2 receptor, and (c) the model representation of probing SARS-CoV-2 binding using atomic force microscopy (AFM). Reprinted from Ref [92]. Open Access publication.

 

Figure 7. A model for the process of SARS-CoV-2 entering host cells in the lungs and attacking other organs. In this process, some transmembrane proteases, such as transmembrane protease serine 2 (TMPRSS2) and a disintegrin metallopeptidase domain 17 (ADAM17) also participate. PICs stand for pro-inflammatory cytokines. These PICs and chemokines can also be produced by the infected cells and inflammatory cells stimulated by viral antigens to activate immunological reactions and inflammatory responses to combat the viruses. Vimentin and clathrin, shown in the figure, are the two proteins, where the former is a type III intermediate filament (IF) protein that is expressed in mesenchymal cells and clathrin is a protein that plays a major role in the formation of coated vesicles. Reprinted from Ref.  [96]. Open Access publication

 

 

                Lividomycin                                                          Burixafor

                     

                      Quisinostat                                                           Fluprofylline

           

                       Pemetrexed                                                Spirofylline

 Edotecarin Chemical Structure                                            diniprofylline Structure

                 Edotecarin                                                                 Diniprofylline

 

Figure 8. Structures of repurposing drug candidates identified to have potential against human ACE2 through a molecular mechanics-assisted structure-based virtual screening by Terali et al. [98]

 

 

Sr No.

Name of compound

Basic biological role

Binding energy

(kcal/mol)

1

Lividomycin

A second-line aminoglycoside antibiotic

-2,145.79

2

Burixafor

A potent and selective CXCR4 antagonist

 

-2,108.82

3

Quisinostat,

A pan-histone deacetylase inhibitor with marked potency toward HDAC1

 

-1,998.77

4

Fluprofylline

 

A bronchodilator, anti-allergic and phosphodiesterase inhibitor

 

-1,785.00

5

Pemetrexed

A novel antimetabolite that inhibits folate-dependent enzymes such as thymidylate synthase

 

-1,602.58

6

Spirofylline

A bronchodilator

-1,541.73

7

Edotecarin

 

A potent DNA topoisomerase 1 inhibitor

-1,312.19

8

Diniprofylline

A bronchodilator and phosphodiesterase inhibitor

 

-1,292.42

    Table 1. The ACE2 inhibition potencies of repurposing drug candidates as evaluated by Terali et al. [98]

Compounds as reported in Figure 8 or Table 1 were the results of a screening of a clinically approved drug library of 7,173 ligands against the receptor ACE2 using molecular docking, followed by energy minimization and rescoring of docked ligands. The authors, Terali et al. [98], have claimed that such studies to find ACE2 inhibitors have been the rare in the literature. Now, according to these authors, all these compounds as listed in Table 1 can be directly tried without any structural modification to fight against SARS-CoV-2 inhibition, or otherwise they may be used as scaffolds to develop still better ACE2 inhibitors.

        Though it is true that study on ACE2 inhibitors that may act against COVID-19 has not picked up, a more recent communication by Gangadevi et al. [99] reported a natural compound, Kobophenal A Figure 9, as a potential inhibitor of ACE2. This compound has been found to block the interaction of ACE2 with S1-RBD of SARS-CoV-2 in vitro with an IC50 of 1.81±0.04 µM and inhibit SARS-CoV-2 viral infection in cells with an EC50 of 71.6 µM. This compound was identified as a potent ACE2 inhibitor through a large library of natural compounds. As a tetramer of resveratrol, Kobophenal A is a stilbenoid and can be isolated from Caragana chamlagu, Caragana sinica, or Carex folliculata seeds. It has been found to exhibit anti-inflammatory activity [100].

               Figure 9. Structure of Kobophenol A, a stilbenoid

     Now, we have come to a point where we can say that an enzyme, the so called ACE2, which was discovered independently by two groups in 2000 [101, 102] has acquired an important status in pathophysiology due to its complex roles in cardiovascular and respiratory systems and still leaves the scope to be studied for its further beneficial roles in other human diseases. It is clear that further studies of its genetic and physiological roles are required to completely understand how it could be therapeutically modulated to be optimally exploited for human health. So far, it has been established that ACE2 is expressed in a number of tissues where most prominent are lung alveolar epithelial cells, kidney, heart, gastrointestinal tract and testes [1, 103]. The prominence of its role in SARS-CoV-2 infection has fuelled the research to exploit it for maximum therapeutic application.

Conclusion

ACE2 is a human homologue of angiotensin-converting enzyme (ACE), an enzyme that has been identified as a fundamental regulator of the renin-angiotensin system (RAS) in humans and is an important target in regulation of blood pressure homeostasis. ACE2 is predominantly expressed in the heart, kidneys and testes, and at lower levels in a wide variety of tissues, particularly the colon and lung and thus implicated in various diseases. It efficiently hydrolyses the potent vasoconstrictor angiotensin II (Ang II) to angiotensin (1–7) [Ang (1-7)] and thus plays an important role in RAS. The first crystal structures of the extracellular metallopeptidase domain of ACE2 in its native and inhibitor-bound states were reported in 2004 by Towler et al. This structural study of Towler et al. facilitated the design of more potent and specific inhibitors of ACE2. As compared to ACE, ACE2 is less widely distributed in the body and differs from ACE in its substrate specificity, functioning exclusively as a carboxypeptidase rather than a peptidyl dipeptidase, but still it has been found to be attached to the membranes of the cells of many crucial organs of the body, such as lungs, arteries, heart, kidney, and intestines, and thus has been recognized as promising drug target for treating many diseases related to these organs. ACE2 was extensively studied in the early 2000’s because of its binding to spike (S) protein of coronaviruses, SARS-CoV (severe acute respiratory syndrome coronavirus) and HCoV-NL3 (human coronavirus-NL3). Now it came to further limelight because of the outbreak of another deadly coronavirus SARS-CoV-2 (formerly 2019-nCoV), whose receptor-binding domain (RBD) has stronger binding affinity with the human ACE2 receptor than that of SARS-CoV, though there is close evolutionary relationship between SARS-CoV-2 and SARS-CoV. This difference in binding affinities of RBDs of SARS-CoV-2 and SARS-CoV is attributed to the difference in their several key amino acid residues. Now ACE2 has become a great target for the development of chemotherapy for COVID-19.

References

  1. Wiese O, Zemlin AE, Pillay TS. Molecules in pathogenesis: angiotensin converting enzyme 2 (ACE2). Journal of Clinical Pathology. 2020 Aug 5.
  2. Towler P, Staker B, Prasad SG, Menon S, Tang J, Parsons T, Ryan D, Fisher M, Williams D, Dales NA, Patane MA. ACE2 X-ray structures reveal a large hinge-bending motion important for inhibitor binding and catalysis. Journal of Biological Chemistry. 2004 Apr 23;279(17):17996-8007.
  3. Natesh R, Schwager SL, Sturrock ED, Acharya KR. Crystal structure of the human angiotensin-converting enzyme–lisinopril complex. Nature. 2003 Jan;421(6922):551-4.
  4. Kim HM, Shin DR, Yoo OJ, Lee H, Lee JO. Crystal structure of Drosophila angiotensin I-converting enzyme bound to captopril and lisinopril. FEBS letters. 2003 Mar 13;538(1-3):65-70. 
  5. Zhang H, Wada J, Hida K, Tsuchiyama Y, Hiragushi K, Shikata K, Wang H, Lin S, Kanwar YS, Makino H. Collectrin, a collecting duct-specific transmembrane glycoprotein, is a novel homolog of ACE2 and is developmentally regulated in embryonic kidneys. Journal of Biological Chemistry. 2001 May 18;276(20):17132-9.
  6. Fülöp V, Böcskei Z, Polgár L. Prolyl oligopeptidase: an unusual β-propeller domain regulates proteolysis. Cell. 1998 Jul 24;94(2):161-70.
  7. Rockel B, Peters J, Kühlmorgen B, Glaeser RM, Baumeister W. A giant protease with a twist: the TPP II complex from Drosophila studied by electron microscopy. The EMBO journal. 2002 Nov 15;21(22):5979-84.
  8. Pantoliano MW, Holmquist B, Riordan JF. Affinity chromatographic purification of angiotensin converting enzyme. Biochemistry. 1984 Feb 1;23(5):1037-42.
  9. Bernstein KE, Welsh SL, Inman JK. A deeply recessed active site in angiotensin-converting enzyme is indicated from the binding characteristics of biotin-spacer-inhibitor reagents. Biochemical and biophysical research communications. 1990 Feb 28;167(1):310-6.
  10. Vickers C, Hales P, Kaushik V, Dick L, Gavin J, Tang J, Godbout K, Parsons T, Baronas E, Hsieh F, Acton S. Hydrolysis of biological peptides by human angiotensin-converting enzyme-related carboxypeptidase. Journal of Biological Chemistry. 2002 Apr 26;277(17):14838-43.
  11. Berman HM, Westbrook J, Feng Z, Gilliland G, Bhat TN, Weissig H, Shindyalov IN, Bourne PE. The protein data bank. Nucleic acids research. 2000 Jan 1;28(1):235-42.
  12. Kim HM, Shin DR, Yoo OJ, Lee H, Lee JO. Crystal structure of Drosophila angiotensin I-converting enzyme bound to captopril and lisinopril. FEBS letters. 2003 Mar 13;538(1-3):65-70. 
  13. Brown CK, Madauss K, Lian W, Beck MR, Tolbert WD, Rodgers DW. Structure of neurolysin reveals a deep channel that limits substrate access. Proceedings of the National Academy of Sciences. 2001 Mar 13;98(6):3127-32.
  14. Arndt JW, Hao B, Ramakrishnan V, Cheng T, Chan SI, Chan MK. Crystal structure of a novel carboxypeptidase from the hyperthermophilic archaeon Pyrococcus furiosus. Structure. 2002 Feb 1;10(2):215-24.
  15. Guy JL, Jackson RM, Acharya KR, Sturrock ED, Hooper NM, Turner AJ. Angiotensin-converting enzyme-2 (ACE2): comparative modeling of the active site, specificity requirements, and chloride dependence. Biochemistry. 2003 Nov 18;42(45):13185-92.
  16. Buenning P, Riordan JF. Activation of angiotensin converting enzyme by monovalent anions. Biochemistry. 1983 Jan 1;22(1):110-6.
  17. Guy JL, Jackson RM, Jensen HA, Hooper NM, Turner AJ. Identification of critical active‐site residues in angiotensin‐converting enzyme‐2 (ACE2) by site‐directed mutagenesis. The FEBS journal. 2005 Jul;272(14):3512-20.
  18. Liu X, Fernandez M, Wouters MA, Heyberger S, Husain A. Arg1098 is critical for the chloride dependence of human angiotensin I-converting enzyme C-domain catalytic activity. Journal of Biological Chemistry. 2001 Sep 7;276(36):33518-25.
  19. Crackower MA, Sarao R, Oudit GY, Yagil C, Kozieradzki I, Scanga SE, Oliveira-dos-Santos AJ, da Costa J, Zhang L, Pei Y, Scholey J. Angiotensin-converting enzyme 2 is an essential regulator of heart function. Nature. 2002 Jun;417(6891):822-8.
  20. Allred AJ, Donoghue M, Acton S, Coffman TM. Regulation of blood pressure by the angiotensin converting enzyme homologue ACE2. In JOURNAL OF THE AMERICAN SOCIETY OF NEPHROLOGY 2002 Sep 1 (Vol. 13, pp. 52A-52A). 1725 I ST, NW STE 510, WASHINGTON, DC 20006 USA: AMER SOC NEPHROLOGY.
  21. Zisman LS, Keller RS, Weaver B, Lin Q, Speth R, Bristow MR, Canver CC. Increased angiotensin-(1-7)–forming activity in failing human heart ventricles: Evidence for upregulation of the angiotensin-converting enzyme homologue ACE2. Circulation. 2003 Oct 7;108(14):1707-12.
  22. Donoghue M, Wakimoto H, Maguire CT, Acton S, Hales P, Stagliano N, Fairchild-Huntress V, Xu J, Lorenz JN, Kadambi V, Berul CI. Heart block, ventricular tachycardia, and sudden death in ACE2 transgenic mice with downregulated connexins. Journal of molecular and cellular cardiology. 2003 Sep 1;35(9):1043-53.
  23. Tikellis C, Johnston CI, Forbes JM, Burns WC, Burrell LM, Risvanis J, Cooper ME. Characterization of renal angiotensin-converting enzyme 2 in diabetic nephropathy. Hypertension. 2003 Mar 1;41(3):392-7.
  24. Brosnihan KB, Neves LA, Joyner J, Averill DB, Chappell MC, Sarao R, Penninger J, Ferrario CM. Enhanced renal immunocytochemical expression of ANG-(1-7) and ACE2 during pregnancy. Hypertension. 2003 Oct 1;42(4):749-53.
  25. Li W, Moore MJ, Vasilieva N, Sui J, Wong SK, Berne MA, Somasundaran M, Sullivan JL, Luzuriaga K, Greenough TC, Choe H. Angiotensin-converting enzyme 2 is a functional receptor for the SARS coronavirus. Nature. 2003 Nov;426(6965):450-4.
  26. Li MY, Li L, Zhang Y, Wang XS. Expression of the SARS-CoV-2 cell receptor gene ACE2 in a wide variety of human tissues. Infectious diseases of poverty. 2020 Dec; 9:1-7. 
  27. Lubbe L, Cozier GE, Oosthuizen D, Acharya KR, Sturrock ED. ACE2 and ACE: structure-based insights into mechanism, regulation and receptor recognition by SARS-CoV. Clinical Science. 2020 Nov;134(21):2851-71.
  28. Oba R, Igarashi A, Kamata M, Nagata K, Takano S, Nakagawa H. The N‐terminal active centre of human angiotensin‐converting enzyme degrades Alzheimer amyloid β‐peptide. European Journal of Neuroscience. 2005 Feb;21(3):733-40.
  29. Zou K, Maeda T, Watanabe A, Liu J, Liu S, Oba R, Satoh YI, Komano H, Michikawa M. Aβ42-to-Aβ40-and angiotensin-converting activities in different domains of angiotensin-converting enzyme. Journal of Biological Chemistry. 2009 Nov 13;284(46):31914-20.
  30. Vickers C, Hales P, Kaushik V, Dick L, Gavin J, Tang J, Godbout K, Parsons T, Baronas E, Hsieh F, Acton S. Hydrolysis of biological peptides by human angiotensin-converting enzyme-related carboxypeptidase. Journal of Biological Chemistry. 2002 Apr 26;277(17):14838-43.
  31. Cozier GE, Lubbe L, Sturrock ED, Acharya KR. Angiotensin‐converting enzyme open for business: structural insights into the subdomain dynamics. The FEBS Journal. 2020 Oct 17.
  32. Hamming I, Timens W, Bulthuis ML, Lely AT, Navis GV, van Goor H. Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland. 2004 Jun;203(2):631-7.
  33. Donoghue M, Hsieh F, Baronas E, Godbout K, Gosselin M, Stagliano N, Donovan M, Woolf B, Robison K, Jeyaseelan R, Breitbart RE. A novel angiotensin-converting enzyme–related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9. Circulation research. 2000 Sep 1;87(5):e1-9.
  34. Keidar S, Kaplan M, Gamliel-Lazarovich A. ACE2 of the heart: from angiotensin I to angiotensin (1–7). Cardiovascular research. 2007 Feb 1;73(3):463-9.
  35. Wang W, McKinnie SM, Farhan M, Paul M, McDonald T, McLean B, Llorens-Cortes C, Hazra S, Murray AG, Vederas JC, Oudit GY. Angiotensin-converting enzyme 2 metabolizes and partially inactivates pyr-apelin-13 and apelin-17: physiological effects in the cardiovascular system. Hypertension. 2016 Aug;68(2):365-77.
  36. Chamsi-Pasha MA, Shao Z, Tang WW. Angiotensin-converting enzyme 2 as a therapeutic target for heart failure. Current heart failure reports. 2014 Mar 1;11(1):58-63.
  37. Mascolo A, Urbanek K, De Angelis A, Sessa M, Scavone C, Berrino L, Rosano GM, Capuano A, Rossi F. Angiotensin II and angiotensin 1–7: which is their role in atrial fibrillation? Heart failure reviews. 2020 Mar;25(2):367-80.
  38. Warner FJ, Smith AI, Hooper NM, Turner AJ. Angiotensin-converting enzyme-2: a molecular and cellular perspective. Cellular and molecular life sciences: CMLS. 2004 Nov 1;61(21):2704-13.
  39. Warner FJ, Guy JL, Lambert DW, Hooper NM, Turner AJ. Angiotensin converting enzyme-2 (ACE2) and its possible roles in hypertension, diabetes and cardiac function. Letters in Peptide Science. 2003 Sep 1;10(5-6):377-85.
  40. Danilczyk U, Penninger JM. Angiotensin-converting enzyme II in the heart and the kidney. Circulation research. 2006 Mar 3;98(4):463-71.
  41. Kuba K, Imai Y, Rao S, Gao H, Guo F, Guan B, Huan Y, Yang P, Zhang Y, Deng W, Bao L. A crucial role of angiotensin converting enzyme 2 (ACE2) in SARS coronavirus–induced lung injury. Nature medicine. 2005 Aug;11(8):875-9.
  42. Imai Y, Kuba K, Rao S, Huan Y, Guo F, Guan B, Yang P, Sarao R, Wada T, Leong-Poi H, Crackower MA. Angiotensin-converting enzyme 2 protects from severe acute lung failure. Nature. 2005 Jul;436(7047):112-6.
  43. Ferrario CM, Jessup J, Gallagher PE, Averill DB, Brosnihan KB, Tallant EA, Smith RD, Chappell MC. Effects of renin-angiotensin system blockade on renal angiotensin-(1-7) forming enzymes and receptors. Kidney international. 2005 Nov 1;68(5):2189-96.
  44. Elased KM, Cunha TS, Gurley SB, Coffman TM, Morris M. New mass spectrometric assay for angiotensin-converting enzyme 2 activity. Hypertension. 2006 May 1;47(5):1010-7.
  45. Shaltout HA, Westwood BM, Averill DB, Ferrario CM, Figueroa JP, Diz DI, Rose JC, Chappell MC. Angiotensin metabolism in renal proximal tubules, urine, and serum of sheep: evidence for ACE2-dependent processing of angiotensin II. American Journal of Physiology-Renal Physiology. 2007 Jan;292(1): F82-91. 
  46. Wysocki J, Ye M, Soler MJ, Gurley SB, Xiao HD, Bernstein KE, Coffman TM, Chen S, Batlle D. ACE and ACE2 activity in diabetic mice. Diabetes. 2006 Jul 1;55(7):2132-9.
  47. Oudit GY, Imai Y, Kuba K, Scholey JW, Penninger JM. The role of ACE2 in pulmonary diseases—relevance for the nephrologist.
  48. Soler MJ, Wysocki J, Batlle D. Angiotensin‐converting enzyme 2 and the kidney. Experimental physiology. 2008 May 1;93(5):549-56.
  49. Gembardt F, Sterner-Kock A, Imboden H, Spalteholz M, Reibitz F, Schultheiss HP, Siems WE, Walther T. Organ-specific distribution of ACE2 mRNA and correlating peptidase activity in rodents. Peptides. 2005 Jul 1;26(7):1270-7. 
  50. Ye M, Wysocki J, Naaz P, Salabat MR, LaPointe MS, Batlle D. Increased ACE 2 and decreased ACE protein in renal tubules from diabetic mice: a renoprotective combination? Hypertension. 2004 May 1;43(5):1120-5. 
  51. Ye M, Wysocki J, William J, Soler MJ, Cokic I, Batlle D. Glomerular localization and expression of angiotensin-converting enzyme 2 and angiotensin-converting enzyme: implications for albuminuria in diabetes. Journal of the American Society of Nephrology. 2006 Nov 1;17(11):3067-75. 
  52. Lely AT, Hamming I, van Goor H, Navis GJ. Renal ACE2 expression in human kidney disease. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland. 2004 Dec;204(5):587-93.
  53. Tallant EA, Clark MA. Molecular mechanisms of inhibition of vascular growth by angiotensin-(1-7). Hypertension. 2003 Oct 1;42(4):574-9.
  54. Yagil Y, Yagil C. Hypothesis: ACE2 modulates blood pressure in the mammalian organism.
  55. Lu N, Yang Y, Wang Y, Liu Y, Fu G, Chen D, Dai H, Fan X, Hui R, Zheng Y. ACE2 gene polymorphism and essential hypertension: an updated meta-analysis involving 11,051 subjects. Molecular biology reports. 2012 Jun 1;39(6):6581-9.
  56. Patel SK, Wai B, Ord M, MacIsaac RJ, Grant S, Velkoska E, Panagiotopoulos S, Jerums G, Srivastava PM, Burrell LM. Association of ACE2 genetic variants with blood pressure, left ventricular mass, and cardiac function in Caucasians with type 2 diabetes. American journal of hypertension. 2012 Feb 1;25(2):216-22.
  57. Fan R, Mao SQ, Gu TL, Zhong FD, Gong ML, Hao LM, Yin FY, Dong CZ, Zhang LN. Preliminary analysis of the association between methylation of the ACE2 promoter and essential hypertension. Molecular medicine reports. 2017 Jun 1;15(6):3905-11.
  58. Hudson LD, Milberg JA, Anardi D, Maunder RJ. Clinical risks for development of the acute respiratory distress syndrome. American journal of respiratory and critical care medicine. 1995 Feb;151(2):293-301. 
  59. Ware LB, Matthay MA. The acute respiratory distress syndrome. New England Journal of Medicine. 2000 May 4;342(18):1334-49.
  60. Kuba K, Imai Y, Penninger JM. Angiotensin-converting enzyme 2 in lung diseases. Current opinion in pharmacology. 2006 Jun 1;6(3):271-6.
  61. Shenoy V, Kwon KC, Rathinasabapathy A, Lin S, Jin G, Song C, Shil P, Nair A, Qi Y, Li Q, Francis J. Oral delivery of Angiotensin-converting enzyme 2 and Angiotensin-(1-7) bioencapsulated in plant cells attenuates pulmonary hypertension. Hypertension. 2014 Dec;64(6):1248-59. 
  62. Hampl V, Herget J, Bíbová J, Baňasová A, Husková Z, Vaňourková Z, Jíchová Š, Kujal P, Vernerová Z, Sadowski J, Červenka L. Intrapulmonary activation of the angiotensin-converting enzyme type 2/angiotensin 1-7/G-protein-coupled Mas receptor axis attenuates pulmonary hypertension in Ren-2 transgenic rats exposed to chronic hypoxia. Physiol. Res. 2015 Jan 1;64(1):25-38.
  63. Yamazato Y, Ferreira AJ, Hong KH, Sriramula S, Francis J, Yamazato M, Yuan L, Bradford CN, Shenoy V, Oh SP, Katovich MJ. Prevention of pulmonary hypertension by angiotensin-converting enzyme 2 gene transfer. Hypertension. 2009 Aug 1;54(2):365-71.
  64. Zhang R, Wu Y, Zhao M, Liu C, Zhou L, Shen S, Liao S, Yang K, Li Q, Wan H. Role of HIF-1α in the regulation ACE and ACE2 expression in hypoxic human pulmonary artery smooth muscle cells. American Journal of Physiology-Lung Cellular and Molecular Physiology. 2009 Oct;297(4):L631-40.
  65. Haga S, Tsuchiya H, Hirai T, Hamano T, Mimori A, Ishizaka Y. A novel ACE2 activator reduces monocrotaline-induced pulmonary hypertension by suppressing the JAK/STAT and TGF-β cascades with restored caveolin-1 expression. Experimental lung research. 2015 Jan 2;41(1):21-31.
  66. Ferreira AJ, Shenoy V, Qi Y, Fraga‐Silva RA, Santos RA, Katovich MJ, Raizada MK. Angiotensin‐converting enzyme 2 activation protects against hypertension‐induced cardiac fibrosis involving extracellular signal‐regulated kinases. Experimental physiology. 2011 Mar 1;96(3):287-94.
  67. Jia H. Pulmonary angiotensin-converting enzyme 2 (ACE2) and inflammatory lung disease. Shock. 2016 Sep 1;46(3):239-48.
  68. Li X, Molina-Molina M, Abdul-Hafez A, Uhal V, Xaubet A, Uhal BD. Angiotensin converting enzyme-2 is protective but downregulated in human and experimental lung fibrosis. American Journal of Physiology-Lung Cellular and Molecular Physiology. 2008 Jul;295(1):L178-85.
  69. Shenoy V, Ferreira AJ, Qi Y, Fraga-Silva RA, Díez-Freire C, Dooies A, Jun JY, Sriramula S, Mariappan N, Pourang D, Venugopal CS. The angiotensin-converting enzyme 2/angiogenesis-(1–7)/Mas axis confers cardiopulmonary protection against lung fibrosis and pulmonary hypertension. American journal of respiratory and critical care medicine. 2010 Oct 15;182(8):1065-72.
  70. Hemnes AR, Rathinasabapathy A, Austin EA, Brittain EL, Carrier EJ, Chen X, Fessel JP, Fike CD, Fong P, Fortune N, Gerszten RE. A potential therapeutic role for angiotensin-converting enzyme 2 in human pulmonary arterial hypertension. European Respiratory Journal. 2018 Jun 1;51(6).
  71. Sharma RK, Stevens BR, Obukhov AG, Grant MB, Oudit GY, Li Q, Richards EM, Pepine CJ, Raizada MK. ACE2 (Angiotensin-Converting Enzyme 2) in cardiopulmonary diseases: ramifications for the control of SARS-CoV-2. Hypertension. 2020 Sep;76(3):651-61.
  72. Santos RA, e Silva AC, Maric C, Silva DM, Machado RP, de Buhr I, Heringer-Walther S, Pinheiro SV, Lopes MT, Bader M, Mendes EP. Angiotensin-(1–7) is an endogenous ligand for the G protein-coupled receptor Mas. Proceedings of the National Academy of Sciences. 2003 Jul 8;100(14):8258-63.
  73. Raizada MK, Ferreira AJ. ACE2: a new target for cardiovascular disease therapeutics. Journal of cardiovascular pharmacology. 2007 Aug 1;50(2):112-9.
  74. Zisman LS, Keller RS, Weaver B, Lin Q, Speth R, Bristow MR, Canver CC. Increased angiotensin-(1-7)–forming activity in failing human heart ventricles: Evidence for upregulation of the angiotensin-converting enzyme homologue ACE2. Circulation. 2003 Oct 7;108(14):1707-12..
  75. Burrell LM, Risvanis J, Kubota E, Dean RG, MacDonald PS, Lu S, Tikellis C, Grant SL, Lew RA, Smith AI, Cooper ME. Myocardial infarction increases ACE2 expression in rat and humans. European heart journal. 2005 Feb 1;26(4):369-75.
  76. Cole-Jeffrey CT, Liu M, Katovich MJ, Raizada MK, Shenoy V. ACE2 and microbiota: emerging targets for cardiopulmonary disease therapy. Journal of cardiovascular pharmacology. 2015 Dec;66(6):540.
  77. Mehta PK, Griendling KK. Angiotensin II cell signaling: physiological and pathological effects in the cardiovascular system. American Journal of Physiology-Cell Physiology. 2007 Jan;292(1):C82-97.
  78. Qi Y, Shenoy V, Wong F, Li H, Afzal A, Mocco J, Sumners C, Raizada MK, Katovich MJ. Lentivirus‐mediated overexpression of angiotensin‐(1–7) attenuated ischaemia‐induced cardiac pathophysiology. Experimental physiology. 2011 Sep 1;96(9):863-74.
  79. Der Sarkissian S, Grobe JL, Yuan L, Narielwala DR, Walter GA, Katovich MJ, Raizada MK. Cardiac overexpression of angiotensin converting enzyme 2 protects the heart from ischemia-induced pathophysiology. Hypertension. 2008 Mar 1;51(3):712-8.
  80. Shenoy V, Ferreira AJ, Qi Y, Fraga-Silva RA, Díez-Freire C, Dooies A, Jun JY, Sriramula S, Mariappan N, Pourang D, Venugopal CS. The angiotensin-converting enzyme 2/angiogenesis-(1–7)/Mas axis confers cardiopulmonary protection against lung fibrosis and pulmonary hypertension. American journal of respiratory and critical care medicine. 2010 Oct 15;182(8):1065-72.
  81. Grobe JL, Mecca AP, Lingis M, Shenoy V, Bolton TA, Machado JM, Speth RC, Raizada MK, Katovich MJ. Prevention of angiotensin II-induced cardiac remodeling by angiotensin-(1–7). American Journal of Physiology-Heart and Circulatory Physiology. 2007 Feb;292(2):H736-42.
  82.  Hernández Prada JA, Ferreira AJ, Katovich MJ, Shenoy V, Qi Y, Santos RA, Castellano RK, Lampkins AJ, Gubala V, Ostrov DA, Raizada MK. Structure-based identification of small-molecule angiotensin-converting enzyme 2 activators as novel antihypertensive agents. Hypertension. 2008 May 1;51(5):1312-7.
  83.  Loot AE, Roks AJ, Henning RH, Tio RA, Suurmeijer AJ, Boomsma F, van Gilst WH. Angiotensin-(1–7) attenuates the development of heart failure after myocardial infarction in rats. Circulation. 2002 Apr 2;105(13):1548-50.
  84.  Rodgers KE, Roda N, Felix JC, Espinoza T, Maldonado S, DiZerega G. Histological evaluation of the effects of angiotensin peptides on wound repair in diabetic mice. Experimental dermatology. 2003 Dec;12(6):784-90.
  85. Oudit GY, Liu GC, Zhong J, Basu R, Chow FL, Zhou J, Loibner H, Janzek E, Schuster M, Penninger JM, Herzenberg AM. Human recombinant ACE2 reduces the progression of diabetic nephropathy. Diabetes. 2010 Feb 1;59(2):529-38.
  86.  Jarajapu YP, Bhatwadekar AD, Caballero S, Hazra S, Shenoy V, Medina R, Kent D, Stitt AW, Thut C, Finney EM, Raizada MK. Activation of the ACE2/angiotensin-(1–7)/Mas receptor axis enhances the reparative function of dysfunctional diabetic endothelial progenitors. Diabetes. 2013 Apr 1;62(4):1258-69.
  87. Lu R, Zhao X, Li J, Niu P, Yang B, Wu H, Wang W, Song H, Huang B, Zhu N, Bi Y. Genomic characterisation and epidemiology of 2019 novel coronavirus: implications for virus origins and receptor binding. The lancet. 2020 Feb 22;395(10224):565-74.
  88. Gupta SP. Progress in Studies on Structural and Remedial Aspects of Newly Born Coronavirus, SARS-CoV-2. Current Topics in Medicinal Chemistry. 2020 Oct 1;20(26):2362-78. 
  89. Belouzard S, Millet JK, Licitra BN, Whittaker GR. Mechanisms of coronavirus cell entry mediated by the viral spike protein. Viruses. 2012 Jun;4(6):1011-33.
  90. Madu IG, Roth SL, Belouzard S, Whittaker GR. Characterization of a highly conserved domain within the severe acute respiratory syndrome coronavirus spike protein S2 domain with characteristics of a viral fusion peptide. Journal of virology. 2009 Aug 1;83(15):7411-21.
  91. Lai AL, Millet JK, Daniel S, Freed JH, Whittaker GR. The SARS-CoV fusion peptide forms an extended bipartite fusion platform that perturbs membrane order in a calcium-dependent manner. Journal of molecular biology. 2017 Dec 8;429(24):3875-92.
  92. Yang J, Petitjean SJ, Koehler M, Zhang Q, Dumitru AC, Chen W, Derclaye S, Vincent SP, Soumillion P, Alsteens D. Molecular interaction and inhibition of SARS-CoV-2 binding to the ACE2 receptor. Nature communications. 2020 Sep 11;11(1):1-0.
  93. Zhou P, Yang XL, Wang XG, Hu B, Zhang L, Zhang W, Si HR, Zhu Y, Li B, Huang CL, Chen HD. A pneumonia outbreak associated with a new coronavirus of probable bat origin. nature. 2020 Mar;579(7798):270-3.
  94. Hamming I, Timens W, Bulthuis ML, Lely AT, Navis GV, van Goor H. Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland. 2004 Jun;203(2):631-7.
  95. Zou X, Chen K, Zou J, Han P, Hao J, Han Z. Single-cell RNA-seq data analysis on the receptor ACE2 expression reveals the potential risk of different human organs vulnerable to 2019-nCoV infection. Frontiers of medicine. 2020 Mar 12:1-8.
  96. Ni W, Yang X, Yang D, Bao J, Li R, Xiao Y, Hou C, Wang H, Liu J, Yang D, Xu Y. Role of angiotensin-converting enzyme 2 (ACE2) in COVID-19. Critical Care. 2020 Dec;24(1):1-0.
  97. Zhang H, Li HB, Lyu JR, Lei XM, Li W, Wu G, Lyu J, Dai ZM. Specific ACE2 expression in small intestinal enterocytes may cause gastrointestinal symptoms and injury after 2019-nCoV infection. International Journal of Infectious Diseases. 2020 Jul 1; 96:19-24. International Journal of Infectious Diseases. 2020 Jul 1; 96:19-24. 
  98. Teralı K, Baddal B, Gülcan HO. Prioritizing potential ACE2 inhibitors in the COVID-19 pandemic: Insights from a molecular mechanics-assisted structure-based virtual screening experiment. Journal of Molecular Graphics and Modelling. 2020 Nov 1;100:107697.
  99. Gangadevi S, Badavath VN, Thakur A, Yin N, De Jonghe S, Acevedo O, Jochmans D, Leyssen P, Wang K, Neyts J, Yujie T. Kobophenol A Inhibits Binding of Host ACE2 Receptor with Spike RBD Domain of SARS-CoV-2, a Lead Compound for Blocking COVID-19. The journal of physical chemistry letters. 2021 Feb 12;12:1793-802.
  100. Cho H, Park JH, Ahn EK, Oh JS. Kobophenol A Isolated from Roots of Caragana sinica (Buc’hoz) Rehder exhibits anti-inflammatory activity by regulating NF-κB nuclear translocation in J774A. 1 cells. Toxicology reports. 2018 Jan 1;5:647-53.
  101. Donoghue M, Hsieh F, Baronas E, Godbout K, Gosselin M, Stagliano N, Donovan M, Woolf B, Robison K, Jeyaseelan R, Breitbart RE. A novel angiotensin-converting enzyme–related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9. Circulation research. 2000 Sep 1;87(5): e1-9. 
  102. Tipnis SR, Hooper NM, Hyde R, Karran E, Christie G, Turner AJ. A human homolog of angiotensin-converting enzyme: cloning and functional expression as a captopril-insensitive carboxypeptidase. Journal of Biological Chemistry. 2000 Oct 27;275(43):33238-43. 
  103. Imai Y, Kuba K, Ohto-Nakanishi T, Penninger JM. Angiotensin-converting enzyme 2 (ACE2) in disease pathogenesis. Circulation Journal. 2010;74(3):405-10.

 

 

 

 

 

 

 

 

Call for Papers

Journal of Molecular Biology and Drug Design