Molecular Aspects of the Cellular Activities of ADP-Ribosylation Factors

Science's STKE  21 Nov 2000:
Vol. 2000, Issue 59, pp. re1
DOI: 10.1126/stke.2000.59.re1

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The adenosine diphosphate-ribosylation factor (Arf) proteins, first identified as cofactors for cholera toxin-catalyzed adenosine diphosphate-ribosylation of Gs, are a family of guanosine triphosphate-binding proteins that regulate membrane traffic and the actin cytoskeleton. Arfs function both constitutively within the secretory pathway and as targets of signal transduction in the cell periphery. Arf activity is in part mediated by binding and recruitment of vesicle coat proteins. Arf proteins also bind to and activate phospholipase D and phosphatidylinositol 4-phosphate 5-kinase, producing phosphatidic acid and phosphatidylinositol 4,5-bisphosphate, respectively. These two lipids contribute to the effects of Arf on membrane traffic and the actin cytoskeleton. In addition, phosphatidic acid and phosphatidylinositol 4,5-bisphosphate are involved in the regulation of Arf, interacting with both guanine nucleotide exchange factors and guanosine triphosphatase-activating proteins. Additional Arf-binding proteins have been identified through two-hybrid screens. The molecular mechanisms by which Arf-binding proteins and phospholipids contribute to Arf's physiologic functions are being discovered.

Abbreviations: Arf, ADP-ribosylation factor; BFA, brefeldin A; COP, coat protein complex; FA, focal adhesion; GAP, GTPase-activating protein; GEF, guanine nucleotide exchange factor; PA, phosphatidic acid; PIP2, phosphatidylinositol 4,5-bisphosphate; PIP3, phosphatidylinositol 3,4,5-trisphosphate.