Cytohesins and centaurins: mediators of PI 3-kinase-regulated Arf signaling

Receptor-activated phosphoinositide (PI) 3-kinases produce Ptdlns(3,4,5)P-3 and its metabolite Ptdlns(3,4)P-2 that function as second messengers in me mbrane recruitment and activation of target proteins. The cytohesin and cen taurin protein families are potential targets for Ptdlns(3,4,5)P-3 that als o regulate and interact with Arf GTPases. Consequently, these families are poised to transduce PI 3-kinase activation into coordinated control of Arf- dependent pathways. Proposed downstream events in PI 3-kinase-regulated Arf cascades include modulation of vesicular trafficking and the actin cytoske leton.