Dok1 mediates high-fat diet-induced adipocyte hypertrophy and obesity through modulation of PPAR-gamma phosphorylation.
Insulin receptor substrate (IRS)-1 and IRS-2 have dominant roles in the action of insulin, but other substrates of the insulin receptor kinase, such as Gab1, c-Cbl, SH2-B and APS, are also of physiological relevance. Although the protein downstream of tyrosine kinases-1 (Dok1) is known to function as a multisite adapter molecule in insulin signaling, its role in energy homeostasis has remained unclear. Here we show that Dok1 regulates adiposity. Expression of Dok1 in white adipose tissue was markedly increased in mice fed a high-fat diet, whereas adipocytes lacking this adapter were smaller and showed a reduced hypertrophic response to this dietary manipulation. Dok1-deficient mice were leaner and showed improved glucose tolerance and insulin sensitivity compared with wild-type mice. Embryonic fibroblasts from Dok1-deficient mice were impaired in adipogenic differentiation, and this defect was accompanied by an increased activity of the protein kinase ERK and a consequent increase in the phosphorylation of peroxisome proliferator-activated receptor (PPAR)-gamma on Ser112. Mutation of this negative regulatory site for the transactivation activity of PPAR-gamma blocked development of the lean phenotype caused by Dok1 ablation. These results indicate that Dok1 promotes adipocyte hypertrophy by counteracting the inhibitory effect of ERK on PPAR-gamma and may thus confer predisposition to diet-induced obesity.
Hosooka
Tetsuya
T
Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
Noguchi
Tetsuya
T
Kotani
Ko
K
Nakamura
Takehiro
T
Sakaue
Hiroshi
H
Inoue
Hiroshi
H
Ogawa
Wataru
W
Tobimatsu
Kazutoshi
K
Takazawa
Kazuo
K
Sakai
Mashito
M
Matsuki
Yasushi
Y
Hiramatsu
Ryuji
R
Yasuda
Tomoharu
T
Lazar
Mitchell A
MA
Yamanashi
Yuji
Y
Kasuga
Masato
M
D017667:Adipocytes / Q000187:drug effects / Q000473:pathology*; D050156:Adipogenesis / Q000187:drug effects; D052436:Adipose Tissue, White / Q000187:drug effects / Q000473:pathology; D050154:Adiposity / Q000187:drug effects; D000818:Animals; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004032:Diet; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005227:Fatty Acids / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D005947:Glucose / Q000378:metabolism; D006984:Hypertrophy; D007328:Insulin / Q000378:metabolism; D051379:Mice; D009765:Obesity / Q000473:pathology*; D047495:PPAR gamma / Q000378:metabolism*; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D004268:DNA-Binding Proteins; C489561:Dok1 protein, mouse; D005227:Fatty Acids; D007328:Insulin; D047495:PPAR gamma; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D010768:Phosphoserine; D048049:Extracellular Signal-Regulated MAP Kinases; D005947:Glucose