Ras homolog enriched in brain (RheB) is a member of the Ras superfamily that was originally identified as an immediate-early gene in brain but is also widely expressed in other tissues. RheB encodes a lipid-anchored, cell membrane protein with five repeats of the RAS-related GTP-binding region. RheB is vital in regulation of growth and cell cycle progression due to its role in the insulin/TOR/S6K signaling pathway.