<strong>O-&beta;-GlcNAcylation,</strong><strong> Chloroquine and </strong><strong>2-Hydroxybenzohydrazine May Hamper SARS-CoV-2 entry to Human via Inhibition of ACE2 Phosphorylation at Ser787 but Also Induce Disruption of Virus-ACE2 Binding</strong>

Abstract

The novel coronavirus COVID-19 disease is extremely contagious and has been spread worldwide. First COVID-19 case was identified in December, 2019 and within three months, more than one million affected cases and over 65,000 deaths have been reported. SARS-coronavirus 2 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 22 April 2020 to the SARS CoV (Severe Acute Respiratory Syndrome corona virus) family. The SARS-CoV-2 enters the human body by binding its viral surface spike protein with the host angiotensinconverting enzyme 2 (ACE2) receptors and cause infection. To prevent the virus entry and its transmission in the human body, we focused on the two domains of ACE2: i) the N-terminal extracellular binding domain (18-740 residues) reported for coronavirus spike interaction, and ii) the C-terminal cytoplasmic region (762-805 residues) to prevent the virus transmission. Therefore, we proposed: i) inhibition of receptor binding domain (RBD) of SARS-CoV-2 and human ACE2 protein may prevent the virus entry to the host and ii) inhibition of phosphorylation at Ser-787 of ACE2 protein may prevent the transmission of the virus in the COVID-19 patients. In the past, the critical role of Ser 787 in human ACE2 protein has been experimentally verified in SARS-CoV transmission, that upon binding to the receptor, SARS-CoV induces CKII-mediated phosphorylation of ACE2 at Ser-787 that in-turn facilitate virus entry to host cells, followed by replication and activation of ACE2, initiates downstream signaling leading to lung fibrosis. Therefore, in this study, we have suggested post-translational modification (PTM) O-β-GlcNAcylation, and two compounds Chloroquine and 2-hydroxybenzohydrazine might share the common pathways to prevent the COVID-19 infection in human. The addition of O-β-GlcNAcylation at same or neighboring Ser/ Thr residues results in phosphorylation inhibition and a change in protein structural and functional confirmations. Thereby, using neural networking methods, we have identified Ser/ Thr residues in ACE2 that are potential sites for phosphorylation and / or O-β-GlcNAcylation. Molecular docking showed that UDP-GlcNAc has more binding affinity with Ser-787 than the phosphoryl group. Moreover, chloroquine and 2hydroxybenzohydrazine also showed great potential to bind at Ser-787 that may result in inhibition of Ser-787 phosphorylation and downstream signaling. Furthermore, O-β-GlcNAcylation, chloroquine and 2-hydroxybenzohydrazine showed their high affinity at ACE2-SARS-CoV-2receptor binding domain that may prevent the entry of SARS-CoV-2 into human body. In conclusion, inhibition of human ACE2 phosphorylation at Ser-787 and ACE2-SARS-CoV-2 binding domain could be promising targets against SARS-CoV-2 infection.

Diabetes and coronavirus (SARS-CoV-2): Molecular mechanism of Metformin intervention and the scientific basis of drug repurposing

“…At the cellular level, the steric hindrance hypothesis on blocking the viral entry by Metformin needs further studies to confirm that AMPKinduced Ser 680 phosphorylation of ACE2 in fact causes a conformational change that affects viral-host cell-binding efficacy. Similar studies on blocking phosphorylation of Ser 787 of ACE2 by other drugs prevented the binding of SARS CoV-2 to the receptor by bringing confirmational changes, and this study can be used as a basis for further exploring the effect of ACE2 phosphorylation on viral binding and its implications on host infections and transmissibility of the virus [130]. Although Metformin is an ideal candidate for host-directed therapies, few contraindications were reported in patients.…”

“…However, controversial reports emerge questioning the protective role of ACE2, whether promoting ACE2 expression promotes or protects from SARS-CoV-2 infection as ACE2 is the port of entry for the virus. Hence, the question arises whether Metformin is beneficial and whether the immunomodulatory and glucose regulation of Metformin outweighs the contradiction behind ACE2 phosphorylation [130]. At the cellular level, the steric hindrance hypothesis on blocking the viral entry by Metformin needs further studies to confirm that AMPKinduced Ser 680 phosphorylation of ACE2 in fact causes a conformational change that affects viral-host cell-binding efficacy.…”