Focal adhesion proteins talin-1 and vinculin negatively affect paxillin phosphorylation and limit retroviral infection.

Many of the early events in retroviral infection are not well understood, but it is known that the host cytoskeleton and signaling pathways play integral roles in various entry and post-entry processes. Focal adhesion complexes act as sites of integration for both cytoskeletal organization and integrin signaling at the cell surface. Here, we show that talin-1 and vinculin, two interacting proteins that localize in focal adhesions to mediate integrin linkage to the actin cytoskeleton, function during retroviral infection. Transient overexpression of either talin-1 or vinculin reduced the susceptibility of human cells to infection with pseudotyped human immunodeficiency virus type 1 (HIV-1) and Moloney murine leukemia virus. In contrast, transient short interfering RNA-mediated knockdown of talin-1 or vinculin increased infection by pseudotyped HIV-1 and simian immunodeficiency virus, demonstrating that the endogenous forms of these proteins also impaired retroviral infection. Talin-1 or vinculin overexpression inhibited infection by retroviruses that entered the cell by either fusion or endocytosis, while analysis of HIV-1 DNA synthesis demonstrated that the block occurred early in infection and prior to the initiation of reverse transcription. Both factors retained antiviral activity in the presence of actin or microtubule depolymerizing agents. Finally, talin-1 and vinculin expression was found to negatively influence tyrosine phosphorylation of paxillin, a major focal adhesion scaffolding protein whose transient knockdown decreased pseudotyped HIV-1 infection. Together, these findings demonstrate that talin-1 and vinculin negatively affect tyrosine phosphorylation of paxillin, a novel positive regulator of HIV-1 infection, and impose an early block to infection by distinct retroviruses.