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Cryo-EM structure of DH898.1 Fab-dimer bound near the CD4 binding site of HIV-1 Env CH848 SOSIP trimer
Structural highlights
FunctionA0A1W6IPB2_9HIV1 Envelope glycoprotein gp160: Oligomerizes in the host endoplasmic reticulum into predominantly trimers. In a second time, gp160 transits in the host Golgi, where glycosylation is completed. The precursor is then proteolytically cleaved in the trans-Golgi and thereby activated by cellular furin or furin-like proteases to produce gp120 and gp41.[HAMAP-Rule:MF_04083] Surface protein gp120: Attaches the virus to the host lymphoid cell by binding to the primary receptor CD4. This interaction induces a structural rearrangement creating a high affinity binding site for a chemokine coreceptor like CXCR4 and/or CCR5. Acts as a ligand for CD209/DC-SIGN and CLEC4M/DC-SIGNR, which are respectively found on dendritic cells (DCs), and on endothelial cells of liver sinusoids and lymph node sinuses. These interactions allow capture of viral particles at mucosal surfaces by these cells and subsequent transmission to permissive cells. HIV subverts the migration properties of dendritic cells to gain access to CD4+ T-cells in lymph nodes. Virus transmission to permissive T-cells occurs either in trans (without DCs infection, through viral capture and transmission), or in cis (following DCs productive infection, through the usual CD4-gp120 interaction), thereby inducing a robust infection. In trans infection, bound virions remain infectious over days and it is proposed that they are not degraded, but protected in non-lysosomal acidic organelles within the DCs close to the cell membrane thus contributing to the viral infectious potential during DCs' migration from the periphery to the lymphoid tissues. On arrival at lymphoid tissues, intact virions recycle back to DCs' cell surface allowing virus transmission to CD4+ T-cells.[HAMAP-Rule:MF_04083] Transmembrane protein gp41: Acts as 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 fusion of viral and target intracellular membranes, 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 target cell membranes. Complete fusion occurs in host cell endosomes and is dynamin-dependent, however some lipid transfer might occur at the plasma membrane. The virus undergoes clathrin-dependent internalization long before endosomal fusion, thus minimizing the surface exposure of conserved viral epitopes during fusion and reducing the efficacy of inhibitors targeting these epitopes. Membranes fusion leads to delivery of the nucleocapsid into the cytoplasm.[HAMAP-Rule:MF_04083] Publication Abstract from PubMedNatural antibodies (Abs) can target host glycans on the surface of pathogens. We studied the evolution of glycan-reactive B cells of rhesus macaques and humans using glycosylated HIV-1 envelope (Env) as a model antigen. 2G12 is a broadly neutralizing Ab (bnAb) that targets a conserved glycan patch on Env of geographically diverse HIV-1 strains using a unique heavy-chain (V(H)) domain-swapped architecture that results in fragment antigen-binding (Fab) dimerization. Here, we describe HIV-1 Env Fab-dimerized glycan (FDG)-reactive bnAbs without V(H)-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques. FDG Abs also recognized cell-surface glycans on diverse pathogens, including yeast and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike. FDG precursors were expanded by glycan-bearing immunogens in macaques and were abundant in HIV-1-naive humans. Moreover, FDG precursors were predominately mutated IgM(+)IgD(+)CD27(+), thus suggesting that they originated from a pool of antigen-experienced IgM(+) or marginal zone B cells. Fab-dimerized glycan-reactive antibodies are a structural category of natural antibodies.,Williams WB, Meyerhoff RR, Edwards RJ, Li H, Manne K, Nicely NI, Henderson R, Zhou Y, Janowska K, Mansouri K, Gobeil S, Evangelous T, Hora B, Berry M, Abuahmad AY, Sprenz J, Deyton M, Stalls V, Kopp M, Hsu AL, Borgnia MJ, Stewart-Jones GBE, Lee MS, Bronkema N, Moody MA, Wiehe K, Bradley T, Alam SM, Parks RJ, Foulger A, Oguin T, Sempowski GD, Bonsignori M, LaBranche CC, Montefiori DC, Seaman M, Santra S, Perfect J, Francica JR, Lynn GM, Aussedat B, Walkowicz WE, Laga R, Kelsoe G, Saunders KO, Fera D, Kwong PD, Seder RA, Bartesaghi A, Shaw GM, Acharya P, Haynes BF Cell. 2021 May 27;184(11):2955-2972.e25. doi: 10.1016/j.cell.2021.04.042. Epub , 2021 May 20. PMID:34019795[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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