Galectin-3 promotes HIV-1 budding through association with Alix and Gag-p6 (170.25)

Abstract Galectin-3 (Gal3), a β-galactoside-binding lectin, has been reported to regulate the functions of a number of immune cell types. We demonstrated that Gal3 is translocated to the immunological synapse in T cells upon T cell receptors engagement and associated with ALG-2-interacting protein X (Alix). Alix is known to coordinate with endosomal sorting complex required for transport (ESCRT) to promote HIV-1 virion release through binding to the HIV-1 Gag-P6 protein. We hypothesized that Gal3 plays a role in HIV-1 viral budding. Co-transfection of Gal3 and HIV-1 plasmids in HEK293T cells indicate that endogenous Gal3 facilitates HIV-1 budding. This effect was inhibited by knocking down Gal3 expression by shRNA. Immunoblotting of trypsin-treated virions and immuno-electron microscopy indicate that Gal3 is mainly located inside the HIV-1 virions. Immunofluorescent staining and coimmunoprecipitation (Co-IP) suggest that Gal3, Alix, and Gag-p6 are colocalized in HIV-1-infected cells. Notably, Gal3 expression was found to promote the association between Alix and Gag-p6 as demonstrated by Co-IP. Co-transfection of Gal3 and HIV-1 plasmids in Alix knocked-down cells indicate that promotion of HIV-1 budding by Gal3 is mediated through Alix. Finally, knocking down Gal3 expression in primary CD4+ T cells resulted in a significant decrease of HIV-1 titer. Our results indicate that endogenous Gal3 facilitates the HIV-1 virus budding through stabilizing the association between Alix and Gag-p6.