The Guanine Nucleotide Exchange Factor ARNO mediates the activation of ARF and phospholipase D by insulin
1 Departments of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
2 Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, U.S.A
3 Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22908, U.S.A
BMC Cell Biology 2003, 4:13 doi:10.1186/1471-2121-4-13Published: 11 September 2003
Phospholipase D (PLD) is involved in many signaling pathways. In most systems, the activity of PLD is primarily regulated by the members of the ADP-Ribosylation Factor (ARF) family of GTPases, but the mechanism of activation of PLD and ARF by extracellular signals has not been fully established. Here we tested the hypothesis that ARF-guanine nucleotide exchange factors (ARF-GEFs) of the cytohesin/ARNO family mediate the activation of ARF and PLD by insulin.
Wild type ARNO transiently transfected in HIRcB cells was translocated to the plasma membrane in an insulin-dependent manner and promoted the translocation of ARF to the membranes. ARNO mutants: ΔCC-ARNO and CC-ARNO were partially translocated to the membranes while ΔPH-ARNO and PH-ARNO could not be translocated to the membranes. Sec7 domain mutants of ARNO did not facilitate the ARF translocation. Overexpression of wild type ARNO significantly increased insulin-stimulated PLD activity, and mutations in the Sec7 and PH domains, or deletion of the PH or CC domains inhibited the effects of insulin.
Small ARF-GEFs of the cytohesin/ARNO family mediate the activation of ARF and PLD by the insulin receptor.