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Cryo-electron microscopy structure of mouse coronavirus spike protein complexed with its murine receptorCryo-electron microscopy structure of mouse coronavirus spike protein complexed with its murine receptor
Structural highlights
Function[SPIKE_CVMA5] S1 attaches the virion to the cell membrane by interacting with murine CEACAM1, initiating the infection.[1] S2 is a class I viral fusion protein. Under the current model, the protein has at least 3 conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and target cell membrane fusion, the coiled coil regions (heptad repeats) assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and plasma cell membranes. Presumably interacts with target cell lipid raft after cell attachment.[2] [CEAM1_MOUSE] Cell adhesion protein that mediates homophilic cell adhesion in a calcium-independent manner (By similarity). Plays a role as coinhibitory receptor in immune response, insulin action and functions also as an activator during angiogenesis (PubMed:16680193, PubMed:17081782, PubMed:18544705, PubMed:21029969, PubMed:21081647, PubMed:22496641, PubMed:22962327, PubMed:23696226). Its coinhibitory receptor function is phosphorylation- and PTPN6 -dependent, which in turn, suppress signal transduction of associated receptors by dephosphorylation of their downstream effectors (PubMed:17081782, PubMed:21029969, PubMed:22496641). Plays a role in immune response, of T-cells, natural killer (NK) and neutrophils (PubMed:17081782, PubMed:23696226, PubMed:22496641, PubMed:21029969). Upon TCR/CD3 complex stimulation, inhibits TCR-mediated cytotoxicity by blocking granule exocytosis by mediating homophilic binding to adjacent cells, allowing interaction with and phosphorylation by LCK and interaction with the TCR/CD3 complex which recruits PTPN6 resulting in dephosphorylation of CD247 and ZAP70 (PubMed:22496641). Also inhibits T-cell proliferation and cytokine production through inhibition of JNK cascade and plays a crucial role in regulating autoimmunity and anti-tumor immunity by inhibiting T-cell through its interaction with HAVCR2 (PubMed:17081782). Upon natural killer (NK) cells activation, inhibit KLRK1-mediated cytolysis of CEACAM1-bearing tumor cells by trans-homophilic interactions with CEACAM1 on the target cell and lead to cis-interaction between CEACAM1 and KLRK1, allowing PTPN6 recruitment and then VAV1 dephosphorylation (PubMed:23696226). Upon neutrophils activation negatively regulates IL1B production by recruiting PTPN6 to a SYK-TLR4-CEACAM1 complex, that dephosphorylates SYK, reducing the production of reactive oxygen species (ROS) and lysosome disruption, which in turn, reduces the activity of the inflammasome (PubMed:22496641). Downregulates neutrophil production by acting as a coinhibitory receptor for CSF3R by downregulating the CSF3R-STAT3 pathway through recruitment of PTPN6 that dephosphorylates CSF3R (PubMed:21029969). Also regulates insulin action by promoting INS clearance and regulating lipogenesis in liver through regulating insulin signaling (PubMed:18544705). Upon INS stimulation, undergoes phosphorylation by INSR leading to INS clearance by increasing receptor-mediated insulin endocytosis. This inernalization promotes interaction with FASN leading to receptor-mediated insulin degradation and to reduction of FASN activity leading to negative regulation of fatty acid synthesis. INSR-mediated phosphorylation also provokes a down-regulation of cell proliferation through SHC1 interaction resulting in decrease coupling of SHC1 to the MAPK3/ERK1-MAPK1/ERK2 and phosphatidylinositol 3-kinase pathways (By similarity). Functions as activator in angiogenesis by promoting blood vessel remodeling through endothelial cell differentiation and migration and in arteriogenesis by increasing the number of collateral arteries and collateral vessel calibers after ischemia (PubMed:16680193, PubMed:22962327). Also regulates vascular permeability through the VEGFR2 signaling pathway resulting in control of nitric oxide production (PubMed:21081647). Downregulates cell growth in response to EGF through its interaction with SHC1 that mediates interaction with EGFR resulting in decrease coupling of SHC1 to the MAPK3/ERK1-MAPK1/ERK2 pathway (PubMed:15467833). Negatively regulates platelet aggregation by decreasing platelet adhesion on type I collagen through the GPVI-FcRgamma complex (PubMed:19008452). Inhibits cell migration and cell scattering through interaction with FLNA; interfers with the interaction of FLNA with RALA (By similarity). Mediates bile acid transport activity in a phosphorylation dependent manner (By similarity). Negatively regulates osteoclastogenesis (PubMed:25490771).[UniProtKB:P13688][UniProtKB:P16573][3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Cell adhesion protein that mediates homophilic cell adhesion in a calcium-independent manner (PubMed:1633107). Promotes populations of T-cells regulating IgA production and secretion associated with control of the commensal microbiota and resistance to enteropathogens (PubMed:23123061).[14] [15] (Microbial infection) In case of murine coronavirus (MHV) infection, serves as receptor for MHV S1 spike glycoprotein.[16] [17] Publication Abstract from PubMedCoronaviruses recognize a variety of receptors using different domains of their envelope-anchored spike protein. How these diverse receptor recognition patterns affect viral entry is unknown. Mouse hepatitis coronavirus (MHV) is the only known coronavirus that uses the N-terminal domain (NTD) of its spike to recognize a protein receptor, CEACAM1a. Here we determined the cryo-EM structure of MHV spike complexed with mouse CEACAM1a. The trimeric spike contains three receptor-binding S1 heads sitting on top of a trimeric membrane-fusion S2 stalk. Three receptor molecules bind to the sides of the spike trimer, where three NTDs are located. Receptor binding induces structural changes in the spike, weakening the interactions between S1 and S2. Using protease sensitivity and negative-stain EM analyses, we further showed that after protease treatment of the spike, receptor binding facilitated the dissociation of S1 from S2, allowing S2 to transition from pre-fusion to post-fusion conformation. Together these results reveal a new role of receptor binding in MHV entry: in addition to its well-characterized role in viral attachment to host cells, receptor binding also induces the conformational change of the spike and hence the fusion of viral and host membranes. Our study provides new mechanistic insight into coronavirus entry and highlights the diverse entry mechanisms used by different viruses. Structure of mouse coronavirus spike protein complexed with receptor reveals mechanism for viral entry.,Shang J, Wan Y, Liu C, Yount B, Gully K, Yang Y, Auerbach A, Peng G, Baric R, Li F PLoS Pathog. 2020 Mar 9;16(3):e1008392. doi: 10.1371/journal.ppat.1008392., eCollection 2020 Mar. PMID:32150576[18] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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