Dataset Information

Understanding how transmembrane domains regulate interactions between human BST-2 and the SARS-CoV-2 accessory protein ORF7a.

ABSTRACT: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID, replicates at intracellular membranes. Bone marrow stromal antigen 2 (BST-2; tetherin) is an antiviral response protein that inhibits transport of viral particles after budding within infected cells. RNA viruses such as SARS-CoV-2 use various strategies to disable BST-2, including use of transmembrane 'accessory' proteins that interfere with BST-2 oligomerization. ORF7a is a small, transmembrane protein present in SARS-CoV-2 shown previously to alter BST-2 glycosylation and function. In this study, we investigated the structural basis for BST-2 ORF7a interactions, with a particular focus on transmembrane and juxtamembrane interactions. Our results indicate that transmembrane domains play an important role in BST-2 ORF7a interactions and mutations to the transmembrane domain of BST-2 can alter these interactions, particularly single-nucleotide polymorphisms in BST-2 that result in mutations such as I28S. Using molecular dynamics simulations, we identified specific interfaces and interactions between BST-2 and ORF7a to develop a structural basis for the transmembrane interactions. Differences in glycosylation are observed for BST-2 transmembrane mutants interacting with ORF7a, consistent with the idea that transmembrane domains play a key role in their heterooligomerization. Overall, our results indicate that ORF7a transmembrane domain interactions play a key role along with extracellular and juxtamembrane domains in modulating BST-2 function.

SUBMITTER: Mann MM

PROVIDER: S-EPMC10197439 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Understanding how transmembrane domains regulate interactions between human BST-2 and the SARS-CoV-2 accessory protein ORF7a.

Mann Madison M MM Hsieh Min-Kang MK Tang James D JD Hart William S WS Lazzara Matthew J MJ Klauda Jeffery B JB Berger Bryan W BW

Biochimica et biophysica acta. Biomembranes 20230519 6

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID, replicates at intracellular membranes. Bone marrow stromal antigen 2 (BST-2; tetherin) is an antiviral response protein that inhibits transport of viral particles after budding within infected cells. RNA viruses such as SARS-CoV-2 use various strategies to disable BST-2, including use of transmembrane 'accessory' proteins that interfere with BST-2 oligomerization. ORF7a is a small, transmembrane protein p ...[more]

PMID: 37211321

Similar Datasets

Project description:Major histocompatibility complex class I (MHC-I) molecules, which are dimers of a glycosylated polymorphic transmembrane heavy chain and the small protein β 2 -microglobulin (β 2 m), bind peptides in the endoplasmic reticulum that are generated by the cytosolic turnover of cellular proteins. In virus-infected cells these peptides may include those derived from viral proteins. Peptide-MHC-I complexes then traffic through the secretory pathway and are displayed at the cell surface where those containing viral peptides can be detected by CD8 + T lymphocytes that kill infected cells. Many viruses enhance their in vivo survival by encoding genes that downregulate MHC-I expression to avoid CD8 + T cell recognition. Here we report that two accessory proteins encoded by SARS-CoV-2, the causative agent of the ongoing COVID-19 pandemic, downregulate MHC-I expression using distinct mechanisms. One, ORF3a, a viroporin, reduces global trafficking of proteins, including MHC-I, through the secretory pathway. The second, ORF7a, interacts specifically with the MHC-I heavy chain, acting as a molecular mimic of β 2 m to inhibit its association. This slows the exit of properly assembled MHC-I molecules from the endoplasmic reticulum. We demonstrate that ORF7a reduces antigen presentation by the human MHC-I allele HLA-A*02:01. Thus, both ORF3a and ORF7a act post-translationally in the secretory pathway to lower surface MHC-I expression, with ORF7a exhibiting a novel and specific mechanism that allows immune evasion by SARS-CoV-2.Significance statementViruses may down-regulate MHC class I expression on infected cells to avoid elimination by cytotoxic T cells. We report that the accessory proteins ORF7a and ORF3a of SARS-CoV-2 mediate this function and delineate the two distinct mechanisms involved. While ORF3a inhibits global protein trafficking to the cell surface, ORF7a acts specifically on MHC-I by competing with β 2 m for binding to the MHC-I heavy chain. This is the first account of molecular mimicry of β 2 m as a viral mechanism of MHC-I down-regulation to facilitate immune evasion.

Project description:As the world continues to fight the coronavirus pandemic caused by SARS‐CoV‐2, we are gaining valuable insights by comparing this virus to other human coronaviruses such as SARS‐CoV and MERS‐CoV that have also caused outbreaks. Coronaviruses infect many animal species, but disease severity varies between strains. Viral accessory proteins are generally implicated in increased infectivity, pathogenicity, and virulence. The accessory protein open reading frame 8 (ORF8), although not essential for viral replication, appears to play a critical role in disease severity by inhibiting multiple pathways of the immune response. Furthermore, the ORF8 gene is found within a highly variable portion of the genome, increasing the possibility of dangerous mutant forms arising. Structure‐based design of therapeutics holds great promise for effective targeting of such rapidly evolving threats. Thus, we designed physical models and computer representations of ORF8, based on the published structure 7JTL, to better evaluate the structural features responsible for viral pathogenicity. ORF8 exists as a homodimer held together by amino acid residues that interact through hydrophobic interactions, hydrogen bonding, a salt bridge, and a disulfide bond. These interactions occur in a region referred to as the covalent interface. Another interface, referred to as the noncovalent interface, exists between separate homodimers and results in oligomerization. The homodimers in the oligomer are held together by an intermolecular beta sheet that is stabilized by an extensive hydrophobic surface. These two dimerization interfaces are unique to SARS‐CoV‐2 and have been proposed to be involved in the protein's ability to evade and suppress the host immune response. The computer and physical representations allow for better visualization of the ORF8 structure to evaluate the role of the multimeric structure. ORF8 has been found to interact with various host proteins, including Interleukin‐17 Receptor A (IL17RA), a pro‐inflammatory cytokine. To further corroborate the existence of this interaction and to better understand the role oligomerization might play in pathogenicity, we assessed the possible interactions of ORF8 (7JTL) and IL17RA (5N9B) through theoretical modeling using available tools such as HDOCK. A better understanding of these inter‐subunit interactions may improve our understanding of the unique mechanism the virus uses to evade the immune system and may be instrumental in the development of effective therapeutics.

Dataset Information

Understanding how transmembrane domains regulate interactions between human BST-2 and the SARS-CoV-2 accessory protein ORF7a.

Publications

Understanding how transmembrane domains regulate interactions between human BST-2 and the SARS-CoV-2 accessory protein ORF7a.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets