Inhibition of HIV-1 endocytosis allows lipid mixing at the plasma membrane, but not complete fusion

Inhibition of HIV-1 endocytosis allows lipid mixing at the plasma membrane, but not complete fusion

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Abstract Background We recently provided evidence that HIV-1 enters HeLa-derived TZM-bl and lymphoid CEMss cells by fusing with endosomes, whereas its fusion with the plasma membrane does not proceed beyond the lipid mixing step.The mechanism of restriction of HIV-1 fusion at the cell surface and/or the factors that aid the virus entry from endosomes remain unclear.Results We examined HIV-1 fusion with a panel of target cells lines and with primary CD4+ T cells.

Kinetic measurements of fusion combined with time-resolved imaging of single viruses further reinforced the notion that HIV-1 enters the cells via endocytosis and fusion with endosomes.Furthermore, we attempted to deliberately redirect virus fusion Course a pied - Accessoires - Casquettetuque to the plasma membrane, using two experimental strategies.First, the fusion reaction was synchronized by pre-incubating the viruses with cells at reduced temperature to allow CD4 and coreceptors engagement, but not the virus uptake or fusion.

Subsequent shift to a physiological temperature triggered accelerated virus uptake followed by entry from endosomes, but did not permit fusion at the cell surface.Second, blocking HIV-1 endocytosis by a small-molecule dynamin inhibitor, dynasore, resulted in transfer of viral lipids to the plasma membrane without any detectable release of the viral content into the cytosol.We also found that a higher concentration of dynasore is required to block the HIV-endosome fusion compared to virus internalization.

Conclusions Our results further support the notion that HIV-1 enters disparate cell types through fusion with endosomes.The block of HIV-1 fusion with the plasma membrane at a post-lipid mixing stage shows that this membrane is Stroller Bag not conducive to fusion pore formation and/or enlargement.The ability of dynasore to interfere with the virus-endosome fusion suggests that dynamin could be involved in two distinct steps of HIV-1 entry - endocytosis and fusion within intracellular compartments.