Chronic endothelin-1 treatment leads to heterologous desensitization of insulin signaling in 3T3-L1 adipocytes.
We recently reported that insulin and endothelin-1 (ET-1) can stimulate GLUT4 translocation via the heterotrimeric G protein G alpha q/11 and through PI3-kinase--mediated pathways in 3T3-L1 adipocytes. Because both hormones stimulate glucose transport through a common downstream pathway, we determined whether chronic ET-1 pretreatment would desensitize these cells to acute insulin signaling. We found that ET-1 pretreatment substantially inhibited insulin-stimulated 2-deoxyglucose uptake and GLUT4 translocation. Cotreatment with the ETA receptor antagonist BQ 610 prevented these effects, whereas inhibitors of G alpha i or G beta gamma were without effect. Chronic ET-1 treatment inhibited insulin-stimulated tyrosine phosphorylation of G alpha q/11 and IRS-1, as well as their association with PI3-kinase and blocked the activation of PI3-kinase activity and phosphorylation of AKT: In addition, chronic ET-1 treatment caused IRS-1 degradation, which could be blocked by inhibitors of PI3-kinase or p70 S6-kinase. Similarly, expression of a constitutively active G alpha q mutant, but not the wild-type G alpha q, led to IRS-1 degradation and inhibited insulin-stimulated phosphorylation of IRS-1, suggesting that the ET-1-induced decrease in IRS-1 depends on G alpha q/11 and PI3-kinase. Insulin-stimulated tyrosine phosphorylation of SHC was also reduced in ET-1 treated cells, resulting in inhibition of the MAPK pathway. In conclusion, chronic ET-1 treatment of 3T3-L1 adipocytes leads to heterologous desensitization of metabolic and mitogenic actions of insulin, most likely through the decreased tyrosine phosphorylation of the insulin receptor substrates IRS-1, SHC, and G alpha q/11.
Ishibashi
K I
KI
Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093-0673, USA.
Imamura
T
T
Sharma
P M
PM
Huang
J
J
Ugi
S
S
Olefsky
J M
JM
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D017667:Adipocytes / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003847:Deoxyglucose / Q000378:metabolism; D004347:Drug Interactions; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000037:antagonists & inhibitors / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D051275:Glucose Transporter Type 4; D020962:Heterotrimeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D019751:Intramolecular Transferases / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D009124:Muscle Proteins; D009842:Oligopeptides / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D050721:Proto-Oncogene Proteins c-cbl; D044022:Receptor, Endothelin A; D015398:Signal Transduction / Q000187:drug effects; D014443:Tyrosine / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
D048868:Adaptor Proteins, Signal Transducing; D003847:Deoxyglucose; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D051275:Glucose Transporter Type 4; D020962:Heterotrimeric GTP-Binding Proteins; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D019751:Intramolecular Transferases; D020928:Mitogen-Activated Protein Kinases; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009842:Oligopeptides; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D050721:Proto-Oncogene Proteins c-cbl; D044022:Receptor, Endothelin A; D014443:Tyrosine; D044767:Ubiquitin-Protein Ligases; C490897:Gab1 protein, mouse; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; C495693:Slc2a4 protein, mouse; C087220:BQ 610; C498016:Gnai2 protein, mouse; C066630:squalene-hopene cyclase; C067419:CBL protein, human; C493849:Cbl protein, mouse