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.