RhoB

RhoB is a small GTPase of the Rho family that functions as a molecular switch in the regulation of the actin cytoskeleton and vesicular trafficking. It is encoded by the RHOB gene in humans. Like other Rho family members, RhoB cycles between an inactive GDP-bound state and an active GTP-bound state, controlled by guanine nucleotide exchange factors that promote activation and GTPase-activating proteins that promote inactivation, with GDP-dissociation inhibitors modulating cytosolic localization.

RhoB is distinguished by its predominant localization to endosomal compartments and by a C-terminal region that allows dual prenylation. Specifically, RhoB can be either farnesylated or geranylgeranylated, and this lipid modification influences its subcellular distribution and signaling outputs.

Functionally, RhoB regulates endosome dynamics, vesicle trafficking, and actin cytoskeleton remodeling. It has been implicated in endosome maturation, recycling, and transport between endosomes and the plasma membrane. It can activate downstream effectors such as ROCK to promote actin polymerization and contractility, and it may influence microtubule-associated trafficking through interactions with other regulators of vesicular transport.

RhoB expression is inducible by cellular stress, inflammation, hypoxia, and DNA damage, and it tends to be rapidly turned over. In humans, RhoB participates in processes such as wound healing and vascular function, and its role in cancer is context-dependent, acting as a tumor suppressor in some settings and as a promoter of tumor progression in others. Because of its involvement in angiogenesis and trafficking, RhoB is of interest as a potential therapeutic target in cancer and vascular diseases.

Compared with the closely related RhoA and RhoC, RhoB has a more prominent endosomal localization and a distinct regulatory repertoire, contributing to its context-specific functions.