Knockdown of TRPC3 with siRNA coupled to carbon nanotubes results in decreased insulin-mediated glucose uptake in adult skeletal muscle cells

• The involvement of Ca2+ in the insulin-mediated signaling cascade, resulting in glucose uptake in skeletal muscle, is uncertain. Here, we test the hypothesis that Ca2+ influx through canonical transient receptor potential 3 (TRPC3) channels modulates insulin-mediated glucose uptake in adult skeletal muscle. Experiments were performed on adult skeletal muscle cells of wild-type (WT) and obese, insulin-resistant ob/ob mice. Application of the diacylglycerol analog 1-oleyl-2-acetyl-sn-glycerol (OAG) induced a nonselective cation current, which was inhibited by the addition of anti-TRPC3 antibody in the patch pipette and smaller in ob/ob than in WT cells. Knockdown of TRPC3, using a novel technique based on small interfering RNA (siRNA) coupled to functionalized carbon nanotubes, resulted in pronounced (similar to 70%) decreases in OAG-induced Ca2+ influx and insulin-mediated glucose uptake. TRPC3 and the insulin-sensitive glucose transporter 4 (GLUT4) coimmunoprecipitated, and immunofluorescence staining showed that they were colocalized in the proximity of the transverse tubular system, which is the predominant site of insulin-mediated glucose transport in skeletal muscle. In conclusion, our results indicate that TRPC3 interacts functionally and physically with GLUT4, and Ca2+ influx through TRPC3 modulates insulin-mediated glucose uptake. Thus, TRPC3 is a potential target for treatment of insulin-resistant conditions.-Lanner, J. T., Bruton, J. D., Assefaw-Redda, Y., Andronache, Z., Zhang, S.- J., Severa, D., Zhang, Z.- B., Melzer, W., Zhang, S.-L., Katz, A., Westerblad, H. Knockdown of TRPC3 with siRNA coupled to carbon nanotubes results in decreased insulin-mediated glucose uptake in adult skeletal muscle cells. FASEB J. 23, 1728-1738 (2009)

Nyckelord

Ca2

sarcolemma

transverse tubules

near-membrane Ca2

colocalization

protein-kinase-c

stimulated glut4 translocation

cation channels

transverse tubules

plasma-membrane

calcium sensor

vesicle fusion

slow-twitch

ca2+ influx

activation

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