Galectin-3 promotes HIV-1 budding via association with Alix and Gag p6

Abstract

Galectin-3 has been reported to regulate the functions of a number of immune cell types. We previously reported that galectin-3 is translocated to immunological synapses in T cells upon T-cell receptor engagement, where it associates with ALG-2-interacting protein X (Alix). Alix is known to coordinate with the endosomal sorting complex required for transport (ESCRT) to promote human immunodeficiency virus (HIV)-1 virion release. We hypothesized that galectin-3 plays a role in HIV-1 viral budding. Cotransfection of cells of the Jurkat T line with galectin-3 and HIV-1 plasmids resulted in increased HIV-1 budding, and suppression of galectin-3 expression by RNAi in Hut78 and primary CD4+ T cells led to reduced HIV-1 budding. We used immunofluorescence microscopy to observe the partial colocalization of galectin-3, Alix and Gag in HIV-1-infected cells. Results from co-immunoprecipitation experiments indicate that galectin-3 expression promotes Alix-Gag p6 association, whereas the results of Alix knockdown suggest that galectin-3 promotes HIV-1 budding through Alix. HIV-1 particles released from galectin-3-expressing cells acquire the galectin-3 protein in an Alix-dependent manner, with proteins primarily residing inside the virions. We also found that the galectin-3 N-terminal domain interacts with the proline-rich region of Alix. Collectively, these results suggest that endogenous galectin-3 facilitates HIV-1 budding by promoting the Alix-Gag p6 association.

Molecular mechanism to recruit galectin-3 into multivesicular bodies for polarized exosomal secretion

“…Furthermore, Gal3 seems to promote HIV budding at the plasma membrane through interaction with Alix (77). Remarkably, Alix overexpression rescues the PSAP-Tsg101 interaction in PSAP-defective virus release (78).…”

Galectins at a glance

“…Galectin-3 also interacts with the endosomal sorting complex required for transport (ESCRT). Yeast two-hybrid analysis revealed interaction of the N-terminal domain of galectin-3 with the ESCRT component ALG-2-interacting protein X (Alix) (Chen et al, 2009), which promotes T-cell receptor downregulation, affects intracellular trafficking of the epidermal growth factor receptor (Liu et al, 2012) and release of human immunodeficiency virus (HIV)-1 (Wang et al, 2014). ESCRT components have fundamental roles in the biogenesis of multivesicular bodies (MVBs), which may provide opportunities to recruit galectin-3 into exosomes that are released from MVBs.…”

Galectin-3 and Its Genetic Variation rs4644 Modulate Enterovirus 71 Infection

“…Detailed methods for acquiring full-length galectin-3 cDNA were described in previous studies [17,22]. Two types of galectin-3 cDNA were subcloned into pEGFP-N1 vector (Clontech, Mountain View, CA, USA): wild-type galectin-3 (G3-WT) and rs4644 A allele (G3-64A), to mimic wild-type galectin-3 and rs4644 AA genotype respectively.…”

“…Increased expression of galectin-3 has been reported in tissues collected from patients with hepatitis B virus and hepatitis C virus infections [15,16]. Galectin-3 also promotes virus budding of human immunodeficiency virus [17]. Among the genetic variants of galectin-3, rs4644 is one of the two major single nucleotide polymorphisms (SNPs) with minor allele frequency of > 5%.…”