TY - JOUR
T1 - Wortmannin and LY294002 inhibit the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes
AU - Smith, L. Keith
AU - Vlahos, Chris J.
AU - Reddy, K. Kishta
AU - Falck, J R
AU - Garner, Charles W.
N1 - Funding Information:
This work was supportedb y NIH Grant DK 42816 (CWG), The Texas Advanced Research Program Grant No. 010674-013(C WG) and The Mizutani Foundationf or Glycoscience( JRF).
PY - 1995/8/30
Y1 - 1995/8/30
N2 - The insulin receptor substrate-1 (IRS-1) is expressed in 3T3-L1 adipocytes and is involved in at least some insulin responses, notably mitogenesis. Chronic exposure to insulin down regulates IRS-1 in these cells by stimulating its degradation (Rice, K.M., Turnbow, M.A. and Garner, C.W. (1993) Biochem. Biophys. Res. Commun. 190, 961-967). This insulin response was completely inhibited by wortmannin and LY294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), two inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase). Neither wortmannin nor LY294002 had any effect on the calcium-dependent degradation of IRS-1 in vitro nor did they inhibit the phosphorylation of IRS-1 on tyrosine in response to insulin in intact cells. Dioctanoyl phosphatidylinositol 3,4,5-trisphosphate (C8-PIP3), a synthetic dioctanoyl analog of the major product of PI 3-kinase, stimulated the calcium-dependent degradation of IRS-1 in vitro. In addition, neomycin, a cationic aminoglycoside antibiotic that binds to phosphoinositides, inhibited the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes and, also, the C8-PIP3-stimulated degradation of IRS-1 in vitro. These results suggest that PI 3-kinase and its 3-phosphoinositide products mediate the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes.
AB - The insulin receptor substrate-1 (IRS-1) is expressed in 3T3-L1 adipocytes and is involved in at least some insulin responses, notably mitogenesis. Chronic exposure to insulin down regulates IRS-1 in these cells by stimulating its degradation (Rice, K.M., Turnbow, M.A. and Garner, C.W. (1993) Biochem. Biophys. Res. Commun. 190, 961-967). This insulin response was completely inhibited by wortmannin and LY294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), two inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase). Neither wortmannin nor LY294002 had any effect on the calcium-dependent degradation of IRS-1 in vitro nor did they inhibit the phosphorylation of IRS-1 on tyrosine in response to insulin in intact cells. Dioctanoyl phosphatidylinositol 3,4,5-trisphosphate (C8-PIP3), a synthetic dioctanoyl analog of the major product of PI 3-kinase, stimulated the calcium-dependent degradation of IRS-1 in vitro. In addition, neomycin, a cationic aminoglycoside antibiotic that binds to phosphoinositides, inhibited the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes and, also, the C8-PIP3-stimulated degradation of IRS-1 in vitro. These results suggest that PI 3-kinase and its 3-phosphoinositide products mediate the insulin-induced down-regulation of IRS-1 in 3T3-L1 adipocytes.
KW - Calcium-dependent protease
KW - IRS-1
KW - LY294002
KW - Phosphatidylinositol 3,4,5-trisphosphate
KW - Phosphatidylinositol 3-kinase
KW - Wortmannin
UR - http://www.scopus.com/inward/record.url?scp=0029101769&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029101769&partnerID=8YFLogxK
U2 - 10.1016/0303-7207(95)03622-E
DO - 10.1016/0303-7207(95)03622-E
M3 - Article
C2 - 8674815
AN - SCOPUS:0029101769
SN - 0303-7207
VL - 113
SP - 73
EP - 81
JO - Molecular and Cellular Endocrinology
JF - Molecular and Cellular Endocrinology
IS - 1
ER -