1-Phosphatidylinositol 3-kinase activity is required for insulin-stimulated glucose transport but not for RAS activation in CHO cells.
Insulin stimulation drives the formation of a complex between tyrosine-phosphorylated insulin receptor substrate 1 (IRS-1) and 1-phosphatidylinositol 3-kinase (PI 3-kinase; ATP:1-phosphatidyl-1D-myo-inositol 3-phosphotransferase, EC 2.7.1.137), a heterodimer consisting of regulatory 85-kDa (p85) and catalytic 110-kDa (p110) subunits. This interaction takes place via the phosphorylated YMXM motifs of IRS-1 and the Src homology region 2 (SH2) domains of p85. In this study, the stable overexpression in a Chinese hamster ovary (CHO) cell line of a mutant p85 alpha (delta p85) protein, which lacks a binding site for p110, disrupted the complex formation between IRS-1 and the catalytic subunit of PI 3-kinase in intact cells during insulin stimulation. Activation of insulin receptor kinase and the tyrosine phosphorylation of IRS-1 remained unaffected. In this cell line, both insulin-stimulated accumulation of phosphatidylinositol 3,4,5-trisphosphate and the insulin-stimulated glucose uptake due to the translocation of GLUT1 glucose transporters were markedly impaired, whereas neither phorbol 12-myristate 13-acetate-stimulated glucose uptake nor the insulin-stimulated activation of RAS was impaired. These results suggest that PI 3-kinase is required for glucose transport in insulin signaling in CHO cells.
Hara
K
K
Second Department of Internal Medicine, Kobe University School of Medicine, Japan.
Yonezawa
K
K
Sakaue
H
H
Ando
A
A
Kotani
K
K
Kitamura
T
T
Kitamura
Y
Y
Ueda
H
H
Stephens
L
L
Jackson
T R
TR
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D016466:CHO Cells; D006224:Cricetinae; D004252:DNA Mutational Analysis; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis; D010750:Phosphoproteins / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013329:Structure-Activity Relationship
D051272:Glucose Transporter Type 1; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009004:Monosaccharide Transport Proteins; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; C060974:phosphatidylinositol 3,4,5-triphosphate; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D016283:Proto-Oncogene Proteins p21(ras); D005947:Glucose