Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles.
GLUT4-containing vesicles cycle between the plasma membrane and intracellular compartments. Insulin promotes GLUT4 exocytosis by regulating GLUT4 vesicle arrival at the cell periphery and its subsequent tethering, docking, and fusion with the plasma membrane. The molecular machinery involved in GLUT4 vesicle tethering is unknown. We show here that Myo1c, an actin-based motor protein that associates with membranes and actin filaments, is required for insulin-induced vesicle tethering in muscle cells. Myo1c was found to associate with both mobile and tethered GLUT4 vesicles and to be required for vesicle capture in the total internal reflection fluorescence (TIRF) zone beneath the plasma membrane. Myo1c knockdown or overexpression of an actin binding-deficient Myo1c mutant abolished insulin-induced vesicle immobilization, increased GLUT4 vesicle velocity in the TIRF zone, and prevented their externalization. Conversely, Myo1c overexpression immobilized GLUT4 vesicles in the TIRF zone and promoted insulin-induced GLUT4 exposure to the extracellular milieu. Myo1c also contributed to insulin-dependent actin filament remodeling. Thus we propose that interaction of vesicular Myo1c with cortical actin filaments is required for insulin-mediated tethering of GLUT4 vesicles and for efficient GLUT4 surface delivery in muscle cells.
Cell Biology Program, Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
Shlomit
S
Boguslavsky
Tim
T
Chiu
Kevin P
KP
Foley
Cesar
C
Osorio-Fuentealba
Costin N
CN
Antonescu
K Ulrich
KU
Bayer
Philip J
PJ
Bilan
Amira
A
Klip
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects; D055785:Gene Knockdown Techniques; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D008856:Microscopy, Fluorescence; D024461:Myosin Type I / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats
D000199:Actins; D051275:Glucose Transporter Type 4; D007328:Insulin; C088340:Myo1c protein, rat; C495694:Slc2a4 protein, rat; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D024461:Myosin Type I