GRB2 and diabetes mellitus: Son of Sevenless homolog 1 (Sos1), another GEF, is also implicated in Rac1 activation in diabetic milieu; a regulator of Sos1, 66kDa proto-oncogene Src homologous-collagen homologue (p66Shc), regulates the of binding of Sos1 with the growth factor receptor-bound protein 2 (Grb2) [51], and in diabetes, the binding of Sos1 with Grb2 is decreased, resulting in Rac1 activation [52].