The Rho proteins interact directly with protein kinases which are likely to serve as downstream effector targets of the activated GTPase. The Rho family of GTPases are involved in the regulation of the actin skeleton. Activation of Rho to the GTP bound state promotes formation of stress fibers and is required for the formation and maintenance of focal adhesions. Pathways stimulated by cytokines, hormones and various forms of stress utilize p21 proteins of the Rho family. Possible mediators for these responses include protein kinase such as p120PKN, and p150 ROKa/Rho-A kinase, myosin light chain (MLC) phosphatase and PIP 5-kinase.