CaMKII-mediated phosphorylation of the myosin motor Myo1c is required for insulin-stimulated GLUT4 translocation in adipocytes.
The unconventional myosin Myo1c has been implicated in insulin-regulated GLUT4 translocation to the plasma membrane in adipocytes. We show that Myo1c undergoes insulin-dependent phosphorylation at S701. Phosphorylation was accompanied by enhanced 14-3-3 binding and reduced calmodulin binding. Recombinant CaMKII phosphorylated Myo1c in vitro and siRNA knockdown of CaMKIIdelta abolished insulin-dependent Myo1c phosphorylation in vivo. CaMKII activity was increased upon insulin treatment and the CaMKII inhibitors CN21 and KN-62 or the Ca(2+) chelator BAPTA-AM blocked insulin-dependent Myo1c phosphorylation and insulin-stimulated glucose transport in adipocytes. Myo1c ATPase activity was increased after CaMKII phosphorylation in vitro and after insulin stimulation of CHO/IR/IRS-1 cells. Expression of wild-type Myo1c, but not S701A or ATPase dead mutant K111A, rescued the inhibition of GLUT4 translocation by siRNA-mediated Myo1c knockdown. These data suggest that insulin regulates Myo1c function via CaMKII-dependent phosphorylation, and these events play a role in insulin-regulated GLUT4 trafficking in adipocytes likely involving Myo1c motor activity.
Yip
Ming Fai
MF
Diabetes and Obesity Research Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia.
Ramm
Georg
G
Larance
Mark
M
Hoehn
Kyle L
KL
Wagner
Mark C
MC
Guilhaus
Michael
M
James
David E
DE
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D048948:14-3-3 Proteins / Q000378:metabolism; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000037:antagonists & inhibitors / Q000502:physiology*; D002460:Cell Line; D006224:Cricetinae; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D007328:Insulin / Q000502:physiology*; D051379:Mice; D024461:Myosin Type I; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport
D048948:14-3-3 Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; C470422:Myo1c protein, mouse; C495693:Slc2a4 protein, mouse; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D024461:Myosin Type I; D009218:Myosins