INSULIN REGULATION OF THE RAS ACTIVATION INACTIVATION CYCLE/

In addition to mediating a number of metabolic functions, insulin also uses mitogenic pathways to maintain cellular homeostasis. Many of the se mitogenic responses are mediated by signals through the small molec ular weight guanine nucleotide binding protein, Pas. In the last decad e, great progress has been made in understanding the molecular mechani sms which regulate the insulin mediated conversion of Pas from its ina ctive, GDP-bound state, to the activated GTP-bound form. More recently , it has been appreciated that insulin also regulates the inactivation of this pathway, namely by uncoupling the protein complexes whose for mation is required for Pas activation. This review addresses molecular mechanism which both positively and negatively regulate this mitogeni c signalling pathway.