title: Nuclear co-repressor (NCoR) is required to maintain insulin sensitivity in C2C12myotubes.
abstract: Nuclear co-repressor (NCoR) regulates peripheral insulin sensitivity; however, its role in modulating insulin sensitivity in skeletal muscle remains elusive. Present study investigated protein expression and effect of NCoR on insulin sensitivity in murine skeletal muscle cell line C2C12. Myotubes as compared to myoblasts of C2C12cells were found to be more sensitive in response to insulin as increase in insulin-stimulated phosphorylation of AKT at serine 473 residue (pAKTS473) was significantly higher in myotubes. Incidentally, reduced protein level of NCoR coincided with differentiation of myoblasts into myotubes of C2C12cells. However, insulin stimulation per se failed to affect protein level of NCoR either in myoblasts or myotubes of C2C12cells. To assess the role of NCoR on insulin sensitivity, NCoR was transiently knocked down using siRNA in myotubes of C2C12. In fact, transient silencing of NCoR led to significant reduction in insulin-stimulated pAKTS473and impaired glucose uptake. This observation is in contrast to published studies where NCoR has been reported to negatively regulate insulin signaling cascade. Furthermore, transient silencing of NCoR failed to improve insulin sensitivity in chronic hyperinsulinemia-induced insulin-resistant model of C2C12cells. Importantly, inhibition of lysosomal protein degradation pathway using ammonium chloride restored protein level of NCoR but failed to increase glucose uptake in serum-starved C2C12myotubes. Collectively, data from present study show differential protein level of NCoR under different cell state (myoblast and myotubes) of C2C12cells and NCoR proves to be vital for maintaining insulin sensitivity in C2C12myotubes.
authors.affiliation: Kusuma School of Biological Sciences (KSBS), Indian Institute of Technology (IIT)-Delhi, Hauz Khas, New Delhi, 110016, India.
authors.forename: Abhijeet K
authors.initials: AK
authors.lastname: Choudhary
authors.affiliation: Kusuma School of Biological Sciences (KSBS), Indian Institute of Technology (IIT)-Delhi, Hauz Khas, New Delhi, 110016, India.
authors.forename: Chinmoy S
authors.initials: CS
authors.lastname: Dey
mesh_terms: D000643:Ammonium Chloride; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D056970:Co-Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance; D007976:Leupeptins / Q000494:pharmacology; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism
chemical_list: D056970:Co-Repressor Proteins; D007328:Insulin; D007976:Leupeptins; D034741:RNA, Small Interfering; D000643:Ammonium Chloride; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: AKT phosphorylation; ammonium chloride; glucose uptake; insulin resistance; lysosomal protein degradation pathway; nuclear co-repressor (NCoR)