O-GlcNAc modification on IRS-1 and Akt2 by PUGNAc inhibits their phosphorylation and induces insulin resistance in rat primary adipocytes.
It has been known that O-linked beta-N-acetylglucosamine (O-GlcNAc) modification of proteins plays an important role in transcription, translation, nuclear transport and signal transduction. The increased flux of glucose through the hexosamine biosynthetic pathway (HBP) and increased O-GlcNAc modification of protein have been suggested as one of the causes in the development of insulin resistance. However, it is not clear at the molecular level, how O-GlcNAc protein modification results in substantial impairment of insulin signaling. To clarify the association of O-GlcNAc protein modification and insulin resistance in rat primary adipocytes, we treated the adipocytes with O-(2-acetamido-2deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc), a potent inhibitor of O-GlcNAcase that catalyzes removal of O-GlcNAc from proteins. Prolonged treatment of PUGNAc (100 microM for 12 h) increased O-GlcNAc modification on proteins in adipocytes. PUGNAc also drastically decreased insulin-stimulated 2-deoxyglucose (2DG) uptake and GLUT4 translocation in adipocytes, indicating that PUGNAc developed impaired glucose utilization and insulin resistance in adipocytes. Interestingly, the O-GlcNAc modification of IRS-1 and Akt2 was increased by PUGNAc, accompanied by a partial reduction of insulin-stimulated phosphorylations of IRS-1 and Akt2. The PUGNAc treatment has no effect on the expression level of GLUT4, whereas O-GlcNAc modification of GLUT4 was increased. These results suggest that the increase of O-GlcNAc modification on insulin signal pathway intermediates, such as IRS-1 and Akt2, reduces the insulin-stimulated phosphorylation of IRS-1 and Akt2, subsequently leading to insulin resistance in rat primary adipocytes.
Department of Biochemistry, College of Medicine, Dongguk University, Gyeongju 780-714, Korea.
Seung Yoon
SY
Park
Jiwon
J
Ryu
Wan
W
Lee
D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D003847:Deoxyglucose / Q000493:pharmacokinetics; D051296:Glucose Transporter Type 5; D006031:Glycosylation; D047468:Immunoprecipitation; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010091:Oximes / Q000494:pharmacology*; D048448:Phenylcarbamates / Q000494:pharmacology*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism; D001619:beta-N-Acetylhexosaminidases / Q000037:antagonists & inhibitors
D051296:Glucose Transporter Type 5; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D009004:Monosaccharide Transport Proteins; D010091:Oximes; D048448:Phenylcarbamates; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; C068836:N-acetylglucosaminono-1,5-lactone O-(phenylcarbamoyl)oxime; D003847:Deoxyglucose; C494923:Akt2 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D001619:beta-N-Acetylhexosaminidases; D000117:Acetylglucosamine