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Vol. 17, Issue 10, 4249-4256, October 2006
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*Department of Biochemistry, Boston University Medical School, Boston, MA 02118; and
Department of Cell Biology, Harvard Medical School, Boston, MA 02115
Submitted April 6, 2006;
Revised June 27, 2006;
Accepted July 18, 2006
Monitoring Editor: Robert Parton
Fodrin or nonerythroid spectrin is an abundant component of the cortical cytoskeletal network in rat adipocytes. Fodrin has a highly punctate distribution in resting cells, and insulin causes a dramatic remodeling of fodrin to a more diffuse pattern. Insulin-mediated remodeling of actin occurs to a lesser extent than does that of fodrin. We show that fodrin interacts with the t-soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) syntaxin 4, and this interaction is increased by insulin stimulation and decreased by prior latrunculin A treatment. Latrunculin A disrupts all actin filaments, inhibits glucose transporter 4 (GLUT4) translocation, and causes fodrin to partially redistribute from the plasma membrane to the cytosol. In contrast, cytochalasin D disrupts only the short actin filament signal, and cytochalasin D neither inhibits GLUT4 translocation nor fodrin redistribution in adipocytes. Together, our data suggest that insulin induces remodeling of the fodrinactin network, which is required for the fusion of GLUT4 storage vesicles with the plasma membrane by permitting their access to the t-SNARE syntaxin 4.
Address correspondence to: Paul F. Pilch (ppilch{at}bu.edu)
Abbreviations used: CytoD, cytochalasin D; GLUT4, glucose transporter 4; HM, heavy microsome; IRAP, insulin-regulated aminopeptidase; LatA, latrunculin A; LM, light microsome; PM, plasma membrane; SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptor; Syn4, syntaxin 4.
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