Knockdown of TRPC3 with siRNA coupled to carbon nanotubes results in decreased insulin-mediated glucose uptake in adult skeletal muscle cells.
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.
Lanner
Johanna T
JT
Karolinska Institutet, Department of Physiology and Pharmacology, 171 77 Stockholm, Sweden. lanner@bcm.tmc.edu
Bruton
Joseph D
JD
Assefaw-Redda
Yohannes
Y
Andronache
Zoita
Z
Zhang
Shi-Jin
SJ
Severa
Denise
D
Zhang
Zhi-Bin
ZB
Melzer
Werner
W
Zhang
Shi-Li
SL
Katz
Abram
A
Westerblad
Håkan
H
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D037742:Nanotubes, Carbon; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism
D004075:Diglycerides; D051275:Glucose Transporter Type 4; D007328:Insulin; D037742:Nanotubes, Carbon; D034741:RNA, Small Interfering; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C038237:1-oleoyl-2-acetylglycerol; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose; D002118:Calcium