Nonhelical leash and alpha-helical structures determine the potency of a peptide antagonist of human T-cell leukemia virus entry

Viral fusion proteins mediate the entry of enveloped viral particles into cells by inducing fusion of the viral and target cell membranes. Activated fusion proteins undergo a cascade of conformational transitions and ultimately resolve into a compact trimer of hairpins or six-helix bundle structure, which pulls the interacting membranes together to promote lipid mixing. Significantly, synthetic peptides based on a C-terminal region of the trimer of hairpins are potent inhibitors of membrane fusion and viral entry, and such peptides are typically extensively α-helical. In contrast, an atypical peptide inhibitor of human T-cell leukemia virus (HTLV) includes α-helical and nonhelical leash segments. We demonstrate that both the C helix and C-terminal leash are critical to the inhibitory activities of these peptides. Amino acid side chains in the leash and C helix extend into deep hydrophobic pockets at the membrane-proximal end of the HTLV type 1 (HTLV-1) coiled coil, and these contacts are necessary for potent antagonism of membrane fusion. In addition, a single amino acid substitution within the inhibitory peptide improves peptide interaction with the core coiled coil and yields a peptide with enhanced potency. We suggest that the deep pockets on the coiled coil are ideal targets for small-molecule inhibitors of HTLV-1 entry into cells. Moreover, the extended nature of the HTLV-1-inhibitory peptide suggests that such peptides may be intrinsically amenable to modifications designed to improve inhibitory activity. Finally, we propose that leash-like mimetic peptides may be of value as entry inhibitors for other clinically important viral infections

散逸と外力のある非線型シュレディンガー方程式における低次元のカオス(ソリトンとカオス,基研研究会「ソリトン系のダイナミクスとそれに関するカオスの問題」,研究会報告)

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Highly specific inhibition of leukaemia virus membrane fusion by interaction of peptide antagonists with a conserved region of the coiled coil of envelope

Abstract Background Human T-cell leukaemia virus (HTLV-1) and bovine leukaemia virus (BLV) entry into cells is mediated by envelope glycoprotein catalyzed membrane fusion and is achieved by folding of the transmembrane glycoprotein (TM) from a rod-like pre-hairpin intermediate to a trimer-of-hairpins. For HTLV-1 and for several virus groups this process is sensitive to inhibition by peptides that mimic the C-terminal α-helical region of the trimer-of-hairpins. Results We now show that amino acids that are conserved between BLV and HTLV-1 TM tend to map to the hydrophobic groove of the central triple-stranded coiled coil and to the leash and C-terminal α-helical region (LHR) of the trimer-of-hairpins. Remarkably, despite this conservation, BLV envelope was profoundly resistant to inhibition by HTLV-1-derived LHR-mimetics. Conversely, a BLV LHR-mimetic peptide antagonized BLV envelope-mediated membrane fusion but failed to inhibit HTLV-1-induced fusion. Notably, conserved leucine residues are critical to the inhibitory activity of the BLV LHR-based peptides. Homology modeling indicated that hydrophobic residues in the BLV LHR likely make direct contact with a pocket at the membrane-proximal end of the core coiled-coil and disruption of these interactions severely impaired the activity of the BLV inhibitor. Finally, the structural predictions assisted the design of a more potent antagonist of BLV membrane fusion. Conclusion A conserved region of the HTLV-1 and BLV coiled coil is a target for peptide inhibitors of envelope-mediated membrane fusion and HTLV-1 entry. Nevertheless, the LHR-based inhibitors are highly specific to the virus from which the peptide was derived. We provide a model structure for the BLV LHR and coiled coil, which will facilitate comparative analysis of leukaemia virus TM function and may provide information of value in the development of improved, therapeutically relevant, antagonists of HTLV-1 entry into cells.</p

Candidate Polyanionic Microbicides Inhibit Human T-Cell Lymphotropic Virus Type 1 Receptor Interactions, Cell-Free Infection, and Cell-Cell Spread

The human T-cell lymphotropic virus type 1 (HTLV-1) is the cause of adult T-cell leukemia and inflammatory diseases including HTLV-1-associated myelopathy/tropical spastic paraparesis. HTLV-1 can be transmitted through sexual contact, mother-to-child transmission, and exposure to contaminated blood. Microbicides are agents that interfere with microbial infectivity at mucous membranes, and candidates are under development for use against sexually transmitted viruses such as human immunodeficiency virus type 1. We previously demonstrated that cell surface polyanionic heparan sulfate proteoglycans bind the HTLV-1 envelope glycoprotein surface subunit gp46, facilitating cell-cell and cell-free virus spread in vitro. We now show, using assays for Env-receptor binding inhibition, Env-induced cell-cell fusion, cell-cell virus spread, and pseudotype HTLV-1 infectivity, that the soluble polyanions PRO 2000 and dextran sulfate are potent inhibitors of HTLV-1 spread in vitro, with PRO 2000 being the more promising candidate. The results of these studies suggest that candidate topical microbicides may be of use in reducing HTLV-1 sexual transmission