Knock down of TRPC3 decreases Ca ²⁺ 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.