title: Phagocytic NADPH oxidase links ARNO-Arf6 signaling pathway in glucose-stimulated insulin secretion from the pancreatic β-cell.
abstract: BACKGROUND
  Recent findings from our laboratory have demonstrated that glucose-stimulated insulin secretion (GSIS) involves interplay between a variety of small G proteins belonging to the Rho (e.g., Cdc42 and Rac1) and ADP-ribosylation factor (e.g., Arf6) subfamilies. Using immunological, pharmacological and molecular biological approaches, we have also identified guanine nucleotide exchange factors (GEFs) for Rac1 (e.g., Tiam1) and Arf6 (e.g., ARNO) in clonal INS-1 832/13 cells, normal rat islets and human islets. As a logical extension to these studies, we investigated, herein, potential downstream signaling steps involved in Arf6/ARNO-mediated GSIS.
  
  
  METHODS
  Using a selective pharmacological inhibitor of ARNO/Arf6 signaling axis (e.g., secinH3) we assessed regulatory roles for Arf6/ARNO in promoting phospholipase D (PLD), phagocytic NADPH oxidase (Nox2), reactive oxygen species (ROS), extracellular-regulated kinases (ERK 1/2) and cofilin (actin-severing protein] signaling steps in clonal INS-1 832/13 cells.
  
  
  RESULTS
  Our data suggested a marked inhibition by secinH3 of glucose-induced PLD activation, ERK1/2 phosphorylation and dephosphorylation of cofilin, suggesting that Arf6/ ARNO signaling mediates PLD, ERK1/2 and cofilin activation in beta-cells. In addition, secinH3 blocked glucose-induced Nox2 activation and associated ROS generation, thus placing Nox downstream to Arf6/ARNO signaling step. Lastly, we also demonstrate a significantly higher cofilin phosphorylation (inactive) in islets derived from type 2 diabetic human donors as well as the Zucker Diabetic Fatty (ZDF) rat, a model for type 2 diabetes.
  
  
  CONCLUSIONS
  Together, our current findings identify signaling steps downstream to ARNO/Arf6 axis leading to insulin secretion.
authors.affiliation: Beta-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center and Pharmaceutical Sciences, Wayne State University, Detroit, MI 48201, USA.
authors.forename: Bhavaani
authors.initials: B
authors.lastname: Jayaram
authors.forename: Anjaneyulu
authors.initials: A
authors.lastname: Kowluru
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors; D051339:Actin Depolymerizing Factors / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D020690:GTPase-Activating Proteins; D005947:Glucose / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D008562:Membrane Glycoproteins / Q000502:physiology*; D008875:Middle Aged; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism / Q000502:physiology*; D010586:Phagocytes / Q000201:enzymology; D010739:Phospholipase D / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D011924:Rats, Zucker; D014230:Triazoles / Q000494:pharmacology
chemical_list: D000089982:ADP-Ribosylation Factor 6; D051339:Actin Depolymerizing Factors; D020690:GTPase-Activating Proteins; D007328:Insulin; D008562:Membrane Glycoproteins; C516025:SecinH3; D014230:Triazoles; C102474:cytohesin-2; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D010739:Phospholipase D; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715349:Arf6 protein, rat; D005947:Glucose