Protein kinase C (PKC) beta modulates serine phosphorylation of insulin receptor substrate-1 (IRS-1)--effect of overexpression of PKCbeta on insulin signal transduction.
In vitro phosphorylation of 180-kDa protein, obtained by immunoprecipitation of adipocyte homogenate with anti-IRS-1 antibody was increased with the addition of conventional PKC in the presence of Ca2+, phosphatidylserine (PS) and diolein (DL). Human purified IRS-1 was phosphorylated by purified conventional PKC (cPKC) in the presence of Ca2+/PS/DL. These results suggest that PKC may have a role in the serine phosphorylation of IRS-1. In order to clarify the inhibitory effect of cPKC on glucose transport mechanism, we examined the overexpression of PKCbeta in cultured adipocytes. Overexpression of PKCbeta in adipocytes markedly induced mobility shift and serine phosphorylation of IRS-1, whereas overexpression of dominant negative PKCbeta (DNPKCbeta) blocked this mobility shift and serine phosphorylation of IRS-1. Insulin (10 nM) increased [3H]2-deoxyglucose (2-DOG) uptake to 200% from basal level (100%) in cultured adipocytes transfected with a vector alone. Overexpression of PKCbeta in adipocytes decreased insulin-induced 2-DOG uptake to 110%, whereas overexpression of DNPKCbeta increased it to 230%. These results suggest that PKCbeta negatively regulates glucose uptake via serine phosphorylation of IRS-1 in rat adipocytes.
Ishizuka
Tatsuo
T
Department of General Internal Medicine, Gifu University Graduate School of Medicine, Gifu, Japan. tishizuk-gif@umin.ac.jp
Kajita
Kazuo
K
Natsume
Yoshiyuki
Y
Kawai
Yasunori
Y
Kanoh
Yoshinori
Y
Miura
Atsushi
A
Ishizawa
Masayoshi
M
Uno
Yoshihiro
Y
Morita
Hiroyuki
H
Yasuda
Keigo
K
D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004591:Electrophoresis, Polyacrylamide Gel; D005799:Genes, Dominant; D006801:Humans; D047468:Immunoprecipitation; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D007527:Isoenzymes / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D008297:Male; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D017434:Protein Structure, Tertiary; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection
C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D007527:Isoenzymes; D010750:Phosphoproteins; D012694:Serine; D003847:Deoxyglucose; D011493:Protein Kinase C