The ability of integrin alpha(v)beta(3) to function as a receptor for foot-and-mouth disease virus is not dependent on the presence of complete subunit cytoplasmic domains

The integrin alpha (nu)beta (3) has been shown to function as one of the integrin receptors on cultured cells for foot-and-mouth disease virus (FMDV), and high-efficiency utilization of the bovine homolog of this integrin is dependent on the cysteine-rich repeat region of the bovine beta (3) subunit. In this study we have examined the role of the cytoplasmic domains of the alpha (nu) and beta (3) subunits in FMDV infection. We have found that truncations or extensions of these domains of either subunit, including deletions removing almost all of the cytoplasmic domains, had little or no effect on the ability of the integrin to function as a receptor for FMDV. The lysosomotropic agent monensin inhibited viral replication in cells transfected with either intact or cytoplasmic domain-truncated alpha (nu)beta (3). In addition, viral replication in transfected cells was inhibited by an alpha (nu)beta (3) function-blocking antibody but not by function-blocking antibodies to three other RGD-directed integrins, suggesting that these integrins are not involved in the infectious process. These results indicate that alterations to the cytoplasmic domains of either subunit, which lead to the inability of the integrin receptor to function normally, do not abolish the ability of the integrin to bind and internalize this viral ligand.