Rho plays a regulatory role in the formation of actin stress fibers and focal adhesions, and it is also involved in integrin-mediated signaling events. To study the role of Rho in ␣ v ␤ 3 /gelsolin-dependent signaling, the HIV-Tat peptide, hemagglutinin (HA)-tagged Rho Val-14 (constitutively active) and Rho Asn-19 (dominant negative) were transduced into avian osteoclasts. Protein transduction by HA-Tat was highly efficient, and 90 -100% of the cells were transduced with HA-tagged proteins. We demonstrate here that Rho Val-14 transduction (100 nM) stimulated gelsolin-associated phosphatidylinositol 3-kinase activity, podosome assembly, stress fiber formation, osteoclast motility, and bone resorption, mimicking osteoclast stimulation by osteopontin/␣ v ␤ 3. The effects of Rho Val-14 transduction stimulation was time-dependent. C3 exoenzyme blocked the effects of RhoVal-14 and induced podosome disassembly, loss of motility, and inhibition of bone resorption. Transduction of Rho Asn-19 produced podosome disassembly, and blocked osteopontin stimulation. These data demonstrate that integrin-dependent activation of phosphoinositide synthesis, actin stress fiber formation, podosome reorganization for osteoclast motility, and bone resorption require Rho stimulation.

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