Mechanism Of The Depolarization-and Contraction-regulated Translocation Of Glucose Transporter4in Skeletal Muscle Cells

Objective:We used two muscle cell lines which both express GLUT4myc, the one are rat L6GLUT4myc cells that are lack of contractile apparatus, and the other are mouse C2C12GLUT4myc cells that can contract under contraction stimuli treatments. The goals of this study are to explore the signaling mechanisms of depolarization-and contraction-stimulated GLUT4myc translocation in these two myotubes.Methods:We used55mM potassium chloride to induce depolarization in L6GLUT4myc myotube and contraction in C2C12GLUT4myc myotube, and then compared the effects on GLUT4myc translocation in L6GLUT4myc myotubes and C2C12GLUT4myc myotubes individually. Time-dependent GLUT4myc translocation by potassium chlolide stimulation were also measured in two cell lines.By using different protein kinase inhibitors, GLUT4myc translocation was measured in C2C12GLUT4myc myotubes. Then we compared the effect of55mM potassium chloride stimulated-depolarization and-contraction on signaling molecule activation by detection of the phosphorylation in two cell lines.Results:55mM potassium chloride acutely stimulates GLUT4myc translocation, and GLUT4myc translocation are time-dependent in L6GLUT4myc myotubes, the maximum of GLUT4myc translocation is1.67±0.41fold(P<0.05) over basal. This is the same in C2C12GLUT4myc myotubes, the maximum of GLUT4myc translocation is1.51±0.15fold(P<0.05) over basal.Depolariation in L6GLUT4myc myotube and constraction in C2C12GLUT4myc myotube were indused by potassium chloride stimulate AMPK, CaMK ? and AS160phosphorylation.In C2C12GLUT4myc myotubes, BTS inhibits58%(P?0.05) GLUT4myc translocation under55mM potassium chloride treatment. BAPTA-AM also inhibits55mM potassium chloride stimulated GLUT4myc translocation by42%(P<0.05), Compound C inhibits49%(P<0.05)55mM potassium ion-stimulated GLUT4myc translocation. And KN93inhibits50%(P<0.05)GLUT4wyc translocation under potassium chloride treatment.Conclusion:1?Potassium chloride acutely stimulates GLUT4myc translocation in L6GLUT4myc myotube and C2C12GLUT4myc myotube, and GLUT4myc translocation are all time-dependent in these two line cells.2?While depolarization and contraction induced by potassium chloride stimulate phosphorylation, signal protein AMPK, CaMK ? and AS160all enhance phosphorylation.3?In C2C12GLUT4myc myotube, contraction?Ca2+and protein kinases AMPK and CaMK II take part in the process of constraction stimulated-GLUT4myc transloction.