RhoA is activated during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is an important human pathogen that can c ause severe and life-threatening respiratory infections in infants and immu nocompromised adults. We have recently shown the RSV F glycoprotein, which mediates viral fusion and entry, interacts with the cellular protein RhoA i n two-hybrid and in vitro binding assays. Whether this interaction occurs i n living cells remains an open question. However, because RhoA signaling is associated with many cellular functions relevant to RSV pathogenesis such as actin cytoskeleton organization, expression of proinflammatory cytokines , and smooth muscle contraction, we asked whether RhoA activation occurred during RSV infection of HEp-2 cells. We found that the amount of isoprenyla ted and membrane-bound RhoA in RSV-infected cultures was increased. Further evidence of RhoA activation was demonstrated by downstream signaling activ ity mediated by RhoA. There was an increase in p130(cas) phosphorylation du ring RSV infection, which was prevented by Y-27632, a specific inhibitor of Rho kinase, or lovastatin, an HMG-CoA reductase inhibitor that reduces the synthesis of groups needed for isoprenylation. In addition, RSV infection of HEp-2 cells resulted in an increase in the formation of actin stress fib ers. Pretreatment of HEp-2 cells with Clostridium botulinum C3 exotoxin, an enzyme that specifically ADP-ribosylates and inactivates RhoA, prevented R SV-induced stress fiber formation. These observations indicate that RhoA an d subsequent downstream signaling events are activated during RSV infection , which has implications for RSV pathogenesis, (C) 2001 Academic Press.