Regulation of adenovirus membrane penetration by the cytoplasmic tail of integrin beta 5

Adenovirus (Ad) cell entry involves sequential interactions with host cell receptors that mediate attachment (CAR), internalization (alpha v beta 3 an d alpha v beta 5), and penetration (alpha v beta 5) of the endosomal membra ne. These events allow the virus to deliver its genome to the nucleus. Whil e integrins alpha v beta 3 and alpha v beta 5 both promote Ad internalizati on into cells, integrin alpha v beta 5 selectively facilitates Ad-mediated membrane permeabilization and endosome rupture. In the experiments reported herein, we demonstrate that the intracellular domain of the integrin beta 5 subunit specifically regulates Ad-mediated membrane permeabilization and gene delivery. CS-1 melanoma cells expressing a truncated integrin beta 5 o r a chimeric (beta 5-beta 3) cytoplasmic tail (CT) supported normal levels of Ad endocytosis but had reduced Ad-mediated gene delivery and membrane pe rmeabilization relative to cells expressing a wild-type integrin beta 5, Th in-section electron microscopy revealed that virion particles were capable of being endocytosed into cells expressing a truncated beta 5CT, but they f ailed to escape cytoplasmic vesicles and translocate to the nucleus. Site-s pecific mutagenesis studies suggest that a C-terminal TVD motif in the beta 5CT plays a major role in Ad membrane penetration.