Signal-induced proliferation 1 (SIPA1) is a member of the SIPA1 family of RapGAPs, a family of mitogen-induced GTPase activating proteins. SIPA1 exhibits a specific GAP activity for Ras-related regulatory proteins Rap1 and Rap2, but not for Ran or other small GTPases. When abnormally or prematurely expressed, SIPA1 may also hamper mitogen-induced cell cycle progression and may increase metastases in human cancers.Synonyms: GTPase-activating protein Spa-1, Signal-induced proliferation-associated protein 1, Sipa-1, Spa-1, p130 SPA-1