title: Cytohesin-1 regulates the Arf6-phospholipase D signaling axis in human neutrophils: impact on superoxide anion production and secretion.
abstract: Polymorphonuclear neutrophil (PMN) stimulation with fMLP stimulates small G proteins such as ADP-ribosylation factors (Arfs) Arf1 and Arf6, leading to phospholipase D (PLD) activation and functions such as degranulation and the oxidative burst. However, the molecular links between fMLF receptors and PLD remain unclear. PMNs express cytohesin-1, an Arf-guanine exchange factor that activates Arfs, and its expression is strongly induced during the acquisition of the neutrophilic phenotype by neutrophil-like cells. The role of cytohesin-1 in the activation of the fMLF-Arf-PLD signaling axis, and the accomplishment of superoxide anion production, and degranulation was investigated in PMNs using the selective inhibitor of cytohesin, Sec 7 inhibitor H3 (secinH3). Cytohesin-1 inhibition with secinH3 leads to Arf6 but not Arf1 inhibition, demonstrating the specificity for Arf6, and fMLF-mediated activation of PLD and of the oxidative burst as well. We observed a decrease in fMLF-mediated protein secretion and expression of cell surface markers corresponding to primary (CD63/myeloperoxidase), secondary (CD66/lactoferrin), and tertiary (matrix metalloproteinase-9) granules in PMNs incubated with secinH3. Similarly, silencing cytohesin-1 or Arf6 in PLB-985 cells negatively affected fMLF-induced activation of PLD, superoxide production, and expression of granule markers on the cell surface. In contrast, stable overexpression of cytohesin-1 in PLB-985 cells enhanced fMLF-induced activation of Arf6, PLD, and NADPH oxidase. The results of this study provide evidence for an involvement of cytohesin-1 in the regulation of the functional responses of human PMNs and link these events, in part at least, to the activation of Arf6.
authors.affiliation: Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du Centre Hospitalier de l'Université Québec-Centre Hospitalier de l'Université Laval, Québec, Canada.
authors.forename: Mohammed-Amine
authors.initials: MA
authors.lastname: El Azreq
authors.forename: Valérie
authors.initials: V
authors.lastname: Garceau
authors.forename: Danielle
authors.initials: D
authors.lastname: Harbour
authors.forename: Christophe
authors.initials: C
authors.lastname: Pivot-Pajot
authors.forename: Sylvain G
authors.initials: SG
authors.lastname: Bourgoin
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D015550:Cell Degranulation / Q000187:drug effects; D002478:Cells, Cultured; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000502:physiology*; D006801:Humans; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D019255:NADPH Oxidases / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D014230:Triazoles / Q000494:pharmacology
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020662:Guanine Nucleotide Exchange Factors; C516025:SecinH3; D014230:Triazoles; C100723:cytohesin-1; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D019255:NADPH Oxidases; D010739:Phospholipase D; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human