ADENOVIRUS ENDOCYTOSIS REQUIRES ACTIN CYTOSKELETON REORGANIZATION MEDIATED BY RHO FAMILY GTPASES

Adenovirus (Ad) endocytosis via alpha(v) integrins requires activation of the lipid kinase phosphatidylinositol-3-OH kinase (PI3K). Previous studies have linked PI3K activity to both the Ras and Rho signaling c ascades, each of which has the capacity to alter the host cell actin c ytoskeleton, Ad interaction with cells also stimulates reorganization of cortical actin filaments and the formation of membrane ruffles (lam ellipodia). We demonstrate here that members of the Rho family of smal l GTP binding proteins, nac and CDC42, act downstream of PI3K to promo te Ad endocytosis, Ad internalization was significantly reduced in cel ls treated with Clostridium difficile toxin B and in cells expressing a dominant-negative Rac or CDC42 but not a H-Ras protein, Viral endocy tosis was also inhibited by cytochalasin D as well as by expression of effector domain mutants of Rac or CDC42 that impair cytoskeletal func tion but not JNK/MAP kinase pathway activation. Thus, Ad endocytosis r equires assembly of the actin cytoskeleton, an event initiated by acti vation of PI3K and, subsequently, Rac and CDC42.