ACE2: A predictor of infectability in SARS-Cov-2

Jul 13, 2022

Angiotensin converting enzyme 2 (ACE-2), is a single-pass type I membrane protein and a zinc metalloprotease of the ACE family. ACE2 encodes for a protein that catalyzes the cleavage of angiotensin I into angiotensin 1-9 and angiotensin II into vasodilator angiotensin 1-7. Human ACE-2 protein consists of 805 amino acids, including a N-terminal signal peptide, a single catalytic domain, a junctional segment of the collectrin domain, a peptidase cleavage site, a TM domain, and a short cytoplasmic tail. It’s theoretical molecular weight: 92 kDa.The encoded protein is a functional receptor for the spike glycoprotein of the human SARS-CoV-2 (Covid-19).

Fig 2. Block diagrams of the angiotensin-converting enzyme 2 (ACE2) gene and ACE2 protein. ACE2 gene, exons (magenta), asterisk indicates coding for zinc-binding site HEMGH. ACE2 protein comprised of N-terminal signal peptide (SP, blue), catalytic carboxypeptidase domain (cyan), junctional segment of the collectrin domain (green), peptidase cleavage site (PC, red), transmembrane domain (TM, yellow), and the C-terminal tail. The large proximal N-terminal ectodomain of the ACE2 protein (red line) can be shed after proteolytic cleavage by endopeptidases, such as ADAM17 and TMPRSS2. This shed segment of ACE2 is named sACE2 (soluble ACE2). sACE2 is a catalytically active serum protein.

Fig 3. Enzymatic cascade of the renin-angiotensin system (RAS) and the key receptor systems. The RAS cascade showing the angiotensin peptide metabolic pathway. Angiotensinogen, as the starting substrate, is cleaved by renin to AngI. AngI is cleaved by ACE to AngII, which is cleaved by ACE2 to Ang(1-7). AngII acts on AT1 and AT2 receptors. Ang(1-7) acts on Mas receptors and counterbalances the AngII/AngII AT1R actions. RAS, renin-angiotensin system; AngI, angiotensin I; AngII, angiotensin II; ACE, angiotensin-converting enzyme; AT1R, angiotensin II type 1 receptor; APA, aminopeptidase A; PCP, prolyl carboxypeptidase; PEP, proline endopeptidase.

Scientific Significance of ACE2

ACE-2 also serves as the receptor for the SARS-CoV and SARS-CoV-2 viruses. Binding of the S1 domain of the SARS Coronavirus Spike protein to ACE-2 initiates viral entry into the host cell.

Hypothesis of ACE2 shedding and SARS-CoV-2 entry.

Cellular ACE2, ADAM17, and TMPRSS2 are all expressed on the cell membrane. After being shed by ADAM17, soluble ACE2 is released from its full-length form to counteract the effects of Ang II signaling. Alternatively, cellular ACE2 is also shed by TMPRSS2, which results in SARS-CoV-2-cell membrane fusion. SARS-CoV-2 RNA is then released into the cytoplasm and viral replication is efficiently processed. Because soluble ACE2 contains the virus binding site, it can also bind to the virus. However, without an intracellular environment, the virus cannot be duplicated.

The primary organs or tissues expressing ACE2 include the heart, lung, brain, oral cavity and nasal mucosa, nasopharynx, kidney, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver and blood vessels.

ACE2 plays a central role in vascular, renal, and myocardial physiology. ACE2 has good potential for use in the treatment of patients with acute respiratory distress syndrome (ARDS), cardiovascular disease, gastrointestinal malnutrition and other viral‑related symptoms.

Several findings suggest that rhACE2 may be a promising drug for those with intolerance to classic renin-angiotensin system inhibitors (RAS inhibitors) or in diseases with elevated angiotensin II. Infused rhACE2 has been evaluated in clinical trials for the treatment of ARDS.

Recently, ACE-2 has become an area of intense therapeutic interest to develop treatments against COVID-19. An in vitro study found that clinical-grade human recombinant soluble ACE2 (hrsACE2) reduced SARS-CoV-2 recovery from vero cells by a factor of 1,000-5,000. Some drugs including remdesivir, lopinavir, sofosbuvir, and daclatasvir that can block the binding of the SARS-CoV-2 S protein to the human ACE2 receptor, are undergoing clinical trials.

Fig 4. The mechanism of action of several key drugs. (A) SARS-CoV2 recognizes and binds to ACE2 of the host cell to enter the cell. (B) As a hemagglutinin inhibitor, arbidol can directly bind to the viral hemagglutinin to block its invasion of the host, and it can also activate an antiviral protein (2,5-oligoadenylate synthase) in the body to prevent Interaction between S protein and host ACE2. (C) Chloroquine phosphate can reduce the interaction of Spike-ACE2 by blocking the glycosylation modification at the end of ACE2, thereby inhibiting virus invasion. (D) Recombinant human soluble ACE2 (hrsACE2) can bind to the virus S protein and compete with the host ACE2 for binding sites to inhibit virus invasion.

Name	Arbidol (ARB)	Chloroquine phosphate (CQ)	Clinical-grade soluble human ACE2 (hrsACE2)
Mechanism	Spike-ACE2 and Affect the virus life cycle	Inhibit the process of virus replication and block terminal glycosylation modification of ACE2	Inhibit lung damage and prevent virus invasion
Pharmacokinetic and toxicological data	EC₅₀=10 μM CC₅₀=20-100 μM	EC₅₀=1.13 μM CC₅₀=100 μM	Not reported (currently undergoing Phase 1 and 2 clinical trials; NCT00886353, NCT01597635)
Applicable stage	Early stage of viral infection	Pneumonia worsening stage	Prevent infection stage; late lung injury stage
Suggested dose	200 mg/day <10 days for adults	1,000 mg/day (twice) for 7 days	25-200 μg/day
Possible adverse reactions	Not reported	May increase the risk of fatal ventricular arrhythmia	May increase the risk of virus infection
Problems to be solved	Standardized animal studies and controlled clinical trials	The gap between in vitro antiviral activity and clinical effect; standardized diagnosis and treatment plan yet to be formulated	The impact of hrsACE2 in the later stages of the disease process

Under Covid-19 infection ACE2 receptor acts as a potent membrane receptor used by the virus to bind and enter the host cells via endocytosis. This decreases the availability of ACE2 receptors on cell membranes resulting in loss of membrane-bound catalytic activity.

Moreover, a study found that the serum levels of ACE2 are significantly higher in highly exposed but uninfected subjects suggesting that high levels of ACE2 in serum may somewhat protect against an active infection without generating a conventional antibody response.

ACE2 Resource Tool Center

Assay Kits for ACE2

OriGene's ACE2 ELISA kit provides sensitive and reliable ACE2 measurements to obtain valuable data from your experiments.

Get your ACE2 Elisa Kit here

Antibodies for ACE2

OriGene has developed highly-specific and sensitive antibodies that recognize native epitopes which can be used in IHC, ELISA, WB. IF, IP etc

Primary Antibodies

Cat# TA803041

Immunohistochemical staining of paraffin-embedded Carcinoma of Human lung tissue using anti-ACE2 mouse monoclonal antibody.

Carrier-Free Antibodies

Cat# CF804152

Immunohistochemical staining of paraffin-embedded Human colon tissue within the normal limits using anti-ACE2 mouse monoclonal antibody.

Primary Antibody Samples

Cat# TA803841S

Immunohistochemical staining of paraffin-embedded Carcinoma of Human kidney tissue using anti-ACE2 mouse monoclonal antibody.

Anti-ACE2 Antibodies

Clones for ACE2

OriGene has developed expression ready plasmids and Lentiviral particles for various species such as human, mouse and rat species.

Tagged/Un-Tagged Clones

Cat# RC208442

HEK293T cells were transfected with the pCMV6-ENTRY control (Cat# PS100001, Left lane) or pCMV6-ENTRY ACE2 (Cat# RC208442, Right lane) cDNA for 48 hrs and lysed

Lentiviral Particles

Cat# RC208442L2V

RC208442L2 was used to prepare Lentiviral particles using TR30037 packaging kit. HEK293T cells were transduced with RC208442L2V particle to overexpress human ACE2-mGFP fusion protein.

Other products for ACE2

Proteins

RNAi

CRISPR kits