Exp Mol Med.  2006 Apr;38(2):180-189.

Implication of phosphorylation of the myosin II regulatory light chain in insulin-stimulated GLUT4 translocation in 3T3-F442A adipocytes

Affiliations
  • 1Department of Physiology University of Ulsan College of Medicine, Seoul 138-736, Korea. yjjang@amc.seoul.kr
  • 2Department of Biochemistry, College of Medicine, Dongguk University, Gyeongju 780-714, Korea.

Abstract

In adipocytes, insulin stimulates glucose transport primarily by promoting the translocation of GLUT4 to the plasma membrane. Requirements for Ca2+/ calmodulin during insulin-stimulated GLUT4 translocation have been demonstrated; however, the mechanism of action of Ca2+ in this process is unknown. Recently, myosin II, whose function in non-muscle cells is primarily regulated by phosphorylation of its regulatory light chain by the Ca2+/calmodulin-dependent myosin light chain kinase (MLCK), was implicated in insulin-stimulated GLUT4 translocation. The present studies in 3T3- F442A adipocytes demonstrate the novel finding that insulin significantly increases phosphorylation of the myosin II RLC in a Ca2+-dependent manner. In addition, ML-7, a selective inhibitor of MLCK, as well as inhibitors of myosin II, such as blebbistatin and 2,3-butanedione monoxime, block insulin- stimulated GLUT4 translocation and subsequent glucose transport. Our studies suggest that MLCK may be a regulatory target of Ca2+/calmodulin and may play an important role in insulin-stimulated glucose transport in adipocytes.

Keyword

calcium signaling; glucose transporter type 4; insulin; myosin type II; myosin-light-chain kinase; phosphorylation
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