G protein-coupled receptor kinase 2 mediates endothelin-1-induced insulin resistance via the inhibition of both Galphaq/11 and insulin receptor substrate-1 pathways in 3T3-L1 adipocytes.
G protein-coupled receptor kinases (GRKs) regulate seven-transmembrane receptors (7TMRs) by phosphorylating agonist-activated 7TMRs. Recently, we have reported that GRK2 can function as a negative regulator of insulin action by interfering with G protein-q/11 alpha-subunit (Galphaq/11) signaling, causing decreased glucose transporter 4 (GLUT4) translocation. We have also reported that chronic endothelin-1 (ET-1) treatment leads to heterologous desensitization of insulin signaling with decreased tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and Galphaq/11, and decreased insulin-stimulated glucose transport in 3T3-L1 adipocytes. In the current study, we have investigated the role of GRK2 in chronic ET-1-induced insulin resistance. Insulin-induced GLUT4 translocation was inhibited by pretreatment with ET-1 for 24 h, and we found that this inhibitory effect was rescued by microinjection of anti-GRK2 antibody or GRK2 short interfering RNA. We further found that GRK2 mediates the inhibitory effects of ET-1 by two distinct mechanisms. Firstly, adenovirus-mediated overexpression of either wild-type (WT)- or kinase-deficient (KD)-GRK2 inhibited Galphaq/11 signaling, including tyrosine phosphorylation of Galphaq/11 and cdc42-associated phosphatidylinositol 3-kinase activity. Secondly, ET-1 treatment caused Ser/Thr phosphorylation of IRS-1 and IRS-1 protein degradation. Overexpression of KD-GRK2, but not WT-GRK2, inhibited ET-1-induced serine 612 phosphorylation of IRS-1 and restored activation of this pathway. Taken together, these results suggest that GRK2 mediates ET-1-induced insulin resistance by 1) inhibition of Galphaq/11 activation, and this effect is independent of GRK2 kinase activity, and 2) GRK2 kinase activity-mediated IRS-1 serine phosphorylation and degradation.
Usui
Isao
I
Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093-0673, USA.
Imamura
Takeshi
T
Babendure
Jennie L
JL
Satoh
Hiroaki
H
Lu
Juu-Chin
JC
Hupfeld
Christopher J
CJ
Olefsky
Jerrold M
JM
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D019332:Endothelin-1 / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D051379:Mice; D009154:Mutation; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000494:pharmacology; D012694:Serine / Q000378:metabolism; D015533:Transcriptional Activation
D000906:Antibodies; D019332:Endothelin-1; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D012694:Serine; D017346:Protein Serine-Threonine Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11