Knock Down of TRPC3 Decreases Ca2+ Influx and Insulin‐mediated Glucose Uptake in Adult Skeletal Muscle

The involvement of Ca2+ in insulin‐mediated glucose uptake in skeletal muscle is uncertain. Here we study the possible role of Ca2+ influx via canonical transient receptor potential 3 (TRPC3) channels in insulin‐mediated glucose uptake. Experiments were performed on adult skeletal mouse muscle fibers. Ca2+ influx and glucose uptake were measured with fluorescent indicators and confocal microscopy. TRPC3 protein expression was knocked down using a novel technique where functionalized carbon nanotubes were used to transfect cells with small interfering RNA. The interaction between TRPC3 and the glucose transporter 4 (GLUT4) was studied with immunoprecipitation and immunofluorescence staining. Knock down of TRPC3 resulted in ∼ 80% decrease in insulin‐mediated glucose uptake. TRPC3 can be activated by diacylglycerol (DAG) and knock down of TRPC3 inhibited the DAG‐induced Ca2+ influx. TRPC3 and GLUT4 co‐immunoprecipitated and showed co‐localization in the proximity of the t‐tubular system, which is the major site of insulin‐mediated glucose transport. In conclusion, TRPC3 interacts functionally and physically with GLUT4 and Ca2+ influx through TRPC3 has a large impact on insulin‐mediated glucose uptake.