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

Abstract

The involvement of Ca(2+) in the insulin-mediated signaling cascade, resulting in glucose uptake in skeletal muscle, is uncertain. Here, we test the hypothesis that Ca(2+) 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 (approximately 70%) decreases in OAG-induced Ca(2+) 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 Ca(2+) influx through TRPC3 modulates insulin-mediated glucose uptake. Thus, TRPC3 is a potential target for treatment of insulin-resistant conditions.

The cholesterol-lowering agent methyl-β-cyclodextrin promotes glucose uptake via GLUT4 in adult muscle fibers and reduces insulin resistance in obese mice

“…The calcium ionophore A23187 increases glucose uptake in L6 myotubes (42) and primary myoblast cultures (52). In skeletal muscle fibers, Ca 2ϩ influx is important for full stimulation of insulin-mediated glucose uptake (12,30,32). Nonetheless, the role played by cytoplasmic calcium signals on glucose uptake remains controversial.…”

Alteration in mitochondrial Ca 2+ uptake disrupts insulin signaling in hypertrophic cardiomyocytes

“…The most widely studied is the canonical signaling cascade constituted by PI3K/Akt, that controls glucose uptake, metabolic activity, and translational responses to insulin [37]. Ca 2+ has also been identified as an important second messenger acting downstream of the insulin receptor and shown to be essential in insulin-mediated glucose uptake in cardiac and skeletal muscle [38][39][40]. Our group showed that Ca 2+ release from the ER through the InsP 3 R is an important component of the Ca 2+ -mediated insulin response in cardiomyocytes [19].…”

“…Mobilization of Ca 2+ is known to facilitate insulinstimulated glucose uptake in diverse cell types [38][39][40].…”

Insulin elicits a ROS-activated and an IP3-dependent Ca2+ release; both impinge on GLUT4 translocation

“…In those cells, decreasing intracellular Ca 2+ signals decreased insulin-stimulated glucose uptake and Akt phosphorylation (Whitehead et al, 2001). In skeletal muscle fibers, Ca 2+ influx is important for full stimulation of glucose uptake (Lanner et al, 2009;Lanner et al, 2006).…”