title: Identification of a role for CLASP2 in insulin action.
abstract: Insulin stimulates the mobilization of glucose transporter 4 (GLUT4) storage vesicles to the plasma membrane, resulting in an influx of glucose into target tissues such as muscle and fat. We present evidence that CLIP-associating protein 2 (CLASP2), a protein previously unassociated with insulin action, is responsive to insulin stimulation. Using mass spectrometry-based protein identification combined with phosphoantibody immunoprecipitation in L6 myotubes, we detected a 4.8-fold increase of CLASP2 in the anti-phosphoserine immunoprecipitates upon insulin stimulation. Western blotting of CLASP2 immunoprecipitates with the phosphoantibody confirmed the finding that CLASP2 undergoes insulin-stimulated phosphorylation, and a number of novel phosphorylation sites were identified. Confocal imaging of L6 myotubes revealed that CLASP2 colocalizes with GLUT4 at the plasma membrane within areas of insulin-mediated cortical actin remodeling. CLASP2 is responsible for directing the distal end of microtubules to the cell cortex, and it has been shown that GLUT4 travels along microtubule tracks. In support of the concept that CLASP2 plays a role in the trafficking of GLUT4 at the cell periphery, CLASP2 knockdown by siRNA in L6 myotubes interfered with insulin-stimulated GLUT4 localization to the plasma membrane. Furthermore, siRNA mediated knockdown of CLASP2 in 3T3-L1 adipocytes inhibited insulin-stimulated glucose transport. We therefore propose a new model for CLASP2 in insulin action, where CLASP2 directs the delivery of GLUT4 to cell cortex landing zones important for insulin action.
authors.affiliation: Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Langlais
authors.forename: James L
authors.initials: JL
authors.lastname: Dillon
authors.forename: April
authors.initials: A
authors.lastname: Mengos
authors.forename: Debra P
authors.initials: DP
authors.lastname: Baluch
authors.forename: Ranna
authors.initials: R
authors.lastname: Ardebili
authors.forename: Danielle N
authors.initials: DN
authors.lastname: Miranda
authors.forename: Xitao
authors.initials: X
authors.lastname: Xie
authors.forename: Bradlee L
authors.initials: BL
authors.lastname: Heckmann
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D017667:Adipocytes / Q000166:cytology; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006706:Homeostasis; D007328:Insulin / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism / Q000502:physiology*; D032446:Myoblasts / Q000378:metabolism; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D014162:Transfection
chemical_list: D000199:Actins; D001786:Blood Glucose; C506523:CLASP2 protein, mouse; C577861:CLASP2 protein, rat; D051275:Glucose Transporter Type 4; D007328:Insulin; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat