RASGRF1 and autoimmune disease: In vitro and in vivo, RASGRF1 has exchange activity not only with H-Ras,32 but also with the Rho family GTPase Rac.33 Additionally, RASGRF1 activity can be regulated by protease-dependent post-translational modifications, and the calpain-dependent cleavage of RASGRF1 enhances its Ras-activating capacity both in vitro and in vivo.34 There is evidence that changes in RASGRF1 expression may lead to autoimmune diseases.