key: cord-0717744-nnhja434
authors: Achour, Ammar
title: Identification of oligopeptides from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) non structural protein 8 (NSP8) and their similarities with type 1 angiotensin II receptor key sites
date: 2021-06-05
journal: Biomed Pharmacother
DOI: 10.1016/j.biopha.2021.111722
sha: 94fb50e73fde69c0d3bb00caa0dd390b6e3bd795
doc_id: 717744
cord_uid: nnhja434

Coronavirus disease 2019 is associated with clinical symptoms including severe inflammatory syndrome and a higher expression of angiotensin II. As a pro-inflammatory mediator, the physiologic effects of angiotensin II are mediated by a G-protein coupled receptor, termed AT(1)R. Following binding, AT(1)R initiates the process of signal desensitization necessary to maintain cellular homeostasis. At the cellular level, this function occurs via the G protein-dependent signaling and the phosphorylation. We describe amino acids similarities between SARS COV-2 nonstructural protein (NSP8) which is associated with intracellular membranes and AT(1)R key sites. Since abnormal activation of AT(1)R receptor leads to a number of physiological disorders, we hypothesize that SARS COV-2 might further interfere with the angiotensin II receptor functions.

Following the isolation of SARS-COV-2 virus and its identification of the causative of severe acute respiratory syndrome (1), many studies have been reported to explain the characteristics of the disease (2, 3) . SARS-COV-2 infects epithelial and endothelial cells, neurons, microglia, and lung macrophages expressing angiotensin-converting enzyme 2 (ACE-2). Moreover, the virus infects also monocytes, macrophages, dendritic cells, and lymphocytes, leading to the development of cytokine storm (4) . The binding of the virus on J o u r n a l P r e -p r o o f ACE2 leads to a downregulation of ACE2 and a higher expression of angiotensin II ( Ang II). The physiologic actions of Ang II is mediated by a G-protein coupled angiotensin II type 1 receptor (AT 1 R). Upon agonist stimulation a rapid internalization and desensitization of AT 1 R is observed. Ang II has been shown to activate nuclear factor kappa-B (NF-κB) through binding to AT 1 R (5). This binding results in the overexpression of inflammation cytokines leading to lymphopenia (5, 6) .

SARS-CoV-2 is characterized by a positive single strand RNA genome (7) . The virus contains several structural proteins like spike, membrane, envelope, nucleoprotein and non-structural proteins. The open reading frame 1ab (ORF1ab) represents approximately 67% of the genome length (8) . It encodes a polyprotein which is processed into 16 nonstructural proteins (Nsp1-16) which are involved in virus processing and replication.

As a non structural viral protein, NSP8 is produced in the first stage of the virus cycle prior genome replication. Therefore, it is characterized as a peptide cofactor of RNA polymerase complex (9) . It has been reported that SARS-CoV-2 non structural proteins match to human proteins (10). NSP8 have previously been shown to affect immune response signaling in the SARS-CoV experimental model (11).

We considered studying the similarity between the NSP8 and type-1 angiotensin II receptor (AT 1 R). In this line of research, we searched for similarities between NSP8

(NCBI Reference Sequence: YP_009742615.1) and type-1 angiotensin II receptor (NCBI Reference Sequence: NP_000676). Using Blast program (NCBI Blast-Protein Sequence), we studied sequences similarities containing at least 9 amino-acid. We were surprised to find the following similarities in a region of NSP8 region (residues 36-96). In this study, we used Needleman-Wunsch algorithm (NW) where double dots indicate identical residues and single dots indicate similarities. The three nsp8 sequences were located in a region (36-181).

The nsp8 KLKKSLNVAK (88-96) peptide shares 90 % similarity (NW score: 23, is characterized by chemical studies (12) . These amino acids are required for G protein activation as previously reported (13) . Consequently, this binding might prevent the coupling to G-alpha-protein of the AT 1 R. These 3 amino acids share similarities with K 36 , K 38 and K 39 of the NSP8 peptide. It is noteworthy to indicate that a part of the peptide (KLKKSLNV) was described as a potential target of autoimmunity (10) . In this report, the nsp8 peptide (AVANGDSEVVLKKLKKSLNV) was suggested to be an autoimmunity component caused by SARS-CoV-2 by sharing homology with a sequence derived from a ubiquitous self antigen (10).

The nsp8 TMLFTMLRK sequence (88-96) is located in a helix type domain as characterized by secondary structure study. It shares 77% similarity (NW score: 19, Identities: 33%, and ERK activation (14) . These are key amino acid residues in AT 1 receptor for Ang II stimulation of p42/44 MAPK activation and are known to interact with any GPCR (15 

The nsp8 sequence QLSEISMDNSPNLA (residues 168-181 share 64 % similarity with type 1 

Nsp8 is thought to be part of the viral replication complex, which is associated with intracellular membranes. It is located in cytoplasmic foci, largely perinuclear. Late in infection, it merges into confluent complexes including nsp7, nsp9 and nsp10. The non structural viral proteins are produced prior to generation of double strand RNA products during virus genome replication. Moreover, it was recently reported that NSP8 is sufficient to suppress protein integration into the cell membrane. By interfering with protein expression in the cell membrane NSP8 can suppress the interferon response (16) .

Following binding to angiotensin II, AT 1 R is submitted to a rapid internalization and desensitization to maintain cellular homeostasis (17) . The binding results in the overexpression of inflammation cytokines called "cytokines storm" observed in covid-19 disease of the second ICL contains basic residues localized in a LPS-binding peptide. These amino acids are required for G protein activation (13) . The third cytoplasmic loop of AT 1 R receptor is implicated in the specificity of receptor coupling to G proteins including Gq-mediated signaling, receptor internalization, and ERK activation (14, 15) . The carboxyl-terminal cytoplasmic domain is involved in G protein-dependent and G protein-independent signaling (15) . Then, the observed similarities between NSP8 and AT 1 R may lighten the function of this receptor in sars-cov 2 infection. By such similarities, we suggest that NSP8 might interfere with protein G modulation (17) . A major factor regulating angiotensin II receptor function is the rapid desensitization following agonist stimulation. Whether the process of signal desensitization by phosphorylation of G-protein-coupled receptor is impaired or activated by NSP8 remains to be determined. The identification of NSP8 domains sharing similarity with the AT 1 receptor could increase our knowledge of how the receptor is regulated in J o u r n a l P r e -p r o o f intracellular following infection. Future studies will investigate the physiological importance of the NSP8 motifs role in the sensitization of AT 1 R.

In summary our study is the first to show similarities between sars cov-2 NSP8 and AT 1 R sites necessary to protein G signaling and receptor modulation. Although it remains unknown what, if any, role these similarities have in virus-infected cells, it suggests that they may provide a comprehension of the pathogenesis of COVID-19. Taken together, our results provide information to explore the physiological actions of NSP8 in covid-19 disease.

The author has no conflict of interest to declare.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors indicates basic residues, : amino acids within LPS-binding site required for G protein activation,  : amino acids required for Gq-mediated signaling, receptor internalization, and ERK activation,  : amino acids involved in G protein-dependent and G protein-independent signaling, : cytoplasmic tail amino acids involved in the agonist-induced desensitization, (a.a) underlined NSP8 a.a which share similarity with AT 1 R.

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