Insulin-induced GLUT4 Movements in C2C12 Myoblasts : Evidence against a Role of Conventional Kinesin Motor Proteins

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Insulin induces translocation of the glucose transporter GLUT4 from intracellularstorage compartment to the plasma membrane via complex mechanisms that requireintact cytoskeletal networks. In cultured adipocytes, conventional kinesin motorproteins have been proposed to mediate GLUT4 movements on microtubules. Itremains, however, unclear whether kinesin motor system plays a similar regulatoryrole in myocytes. We addressed this issue using C2C12 myoblasts, which have now beenshown to express both heavy and light chains of conventional kinesin. In these cells,overexpression of either wild-type kinesin light chain 2 (KLC2) or itsphosphorylation-defective mutant did not significantly affect insulin-stimulatedtranslocation of exofacial Myc-tagged GLUT4-green fluorescent protein to the cellsurface and its subsequent externalization. Likewise, a dominant-negative mutant ofKLC2 had no marked effect on GLUT4 movements in this cell type. These resultssuggest that conventional kinesin is dispensable for insulin-induced GLUT4translocation in cultured myoblasts and may thus reveal a cell-type specific role of themicrotubules-based cytoskeleton in glucose transport in response to insulin.