Regulates a signal transduction pathway linking plasma membrane receptors to the assembly of focal adhesions and actin stress fibers. Serves as a microtubule-dependent signal that is required for the myosin contractile ring formation during cell cycle cytokinesis. Regulates apical junction formation in bronchial epithelial cells (By similarity). Translocates to the equatorial region before furrow formation in a ECT2-dependent manner. Detected in embryonic notochord. Belongs to the small GTPase superfamily. Rho family.