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(Journal of Leukocyte Biology. 2002;71:718-728.)
© 2002 by Society for Leukocyte Biology

ARNO but not cytohesin-1 translocation is phosphatidylinositol 3-kinase-dependent in HL-60 cells

Sylvain G. Bourgoin*, Martin G. Houle*, Indrapal N. Singh{dagger}, Danielle Harbour*, Steve Gagnon*, Andrew J. Morris{ddagger} and David N. Brindley{dagger}

* Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Pavillon CHUL et Département d’Anatomie-Physiologie, Faculté de Médecine, Université Laval, Québec, Canada;
{ddagger} Department of Pharmacological Sciences and the Institute for Cell and Developmental Biology, Stony Brook Health Science Center, Stony Brook, New York; and
{dagger} Signal Transduction Laboratories, Department of Biochemistry and Lipid and Lipoprotein Research Group, University of Alberta, Edmonton, Canada

Correspondence: Sylvain G. Bourgoin, Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ, Pavillon CHUL, Local T1-49, 2705 Boulevard Laurier, Ste-Foy, Québec, G1V 4G2, Canada. E-mail: sylvain.bourgoin{at}crchul.ulaval.ca

Cytohesin-1 and ARNO are guanine nucleotide-exchange factors (GEFs) for ADP-ribosylation factor (Arf). Here, we show that ARNO is expressed in HL-60 cells and established that granulocytic differentiation induced with Me2SO stimulated cytohesin-1 but not ARNO expression. Cytohesin-1 levels in HL-60 granulocytes were similar to those in human neutrophils. Me2SO-differentiated HL-60 cells expressed ARNO and cytohesin-1 isoforms with a diglycine and a triglycine motif in their PH domains, respectively. In vitro, ARNO diglycine and cytohesin-1 triglycine enhanced phospholipase D1 (PLD1) activation by Arf1 with near-maximal effects at 250 nM. These effects were marked particularly at low Mg2+ concentrations. PLD activation was well-correlated with GTP binding to Arf1, and cytohesin-1 was always more potent than ARNO in the PLD- and GTP-binding assays. Increasing Mg2+ concentrations reduced PLD and Arf1 activation by Arf-GEFs. fMetLeuPhe and phorbol 12-myristate 13-acetate stimulated ARNO and cytohesin-1 as well as Arf1 translocation to HL-60 cell membranes. fMetLeuPhe-mediated ARNO recruitment, but not cytohesin-1 and Arf1 translocation, was blocked by phosphatidylinositol 3-kinase inhibitors. The combined results demonstrate that cytohesin-1 triglycine participates in a major phosphatidylinositol 3-kinase-independent pathway linking cell-surface receptors to Arf1 activation and translocation in human granulocytes.

Key Words: Sec7 • ADP-ribosylation factor • pleckstrin homology domain • RhoA • guanine nucleotide-exchange factors • inflammation




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