Evidence for a regulatory role of Cullin-RING E3 ubiquitin ligase 7 in insulin signaling.
Dysfunctional regulation of signaling pathways downstream of the insulin receptor plays a pivotal role in the pathogenesis of insulin resistance and type 2 diabetes. In this study we report both in vitro and in vivo experimental evidence for a role of Cullin-RING E3 ubiquitin ligase 7 (CRL7) in the regulation of insulin signaling and glucose homeostasis. We show that Cul7(-/-) mouse embryonic fibroblasts displayed enhanced AKT and Erk MAP kinase phosphorylation upon insulin stimulation. Depletion of CUL7 by RNA interference in C2C12 myotubes led to increased activation of insulin signaling pathways and cellular glucose uptake, as well as a reduced capacity of these cells to execute insulin-induced degradation of insulin receptor substrate 1 (IRS1). In vivo, heterozygosity of either Cul7 or Fbxw8, both key components of CRL7, resulted in elevated PI3 kinase/AKT activation in skeletal muscle tissue upon insulin stimulation when compared to wild-type controls. Finally, Cul7(+/-) or Fbxw8(+/-) mice exhibited enhanced insulin sensitivity and plasma glucose clearance. Collectively, our findings point to a yet unrecognized role of CRL7 in insulin-mediated control of glucose homeostasis by restraining PI3 kinase/AKT activities in skeletal muscle cells.
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.
Florian
F
Scheufele
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.
Benjamin
B
Wolf
German Institute of Human Nutrition Potsdam-Rehbrücke, Department of Clinical Nutrition, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.|Departments of Biochemistry, Medicine (Endocrinology) and Obstetrics & Gynecology and Women's Health, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Michael
M
Kruse
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.
Thomas
T
Hartmann
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.
Justine
J
Lempart
Walther-Straub-Institute of Pharmacology and Toxicology, Ludwig-Maximilians-University, Goethestraße 33, 80336 Munich, Germany.
Susanne
S
Mühlich
German Institute of Human Nutrition Potsdam-Rehbrücke, Department of Clinical Nutrition, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.|Department of Endocrinology, Diabetes and Nutrition, Charité University Medicine, 10117 Berlin, Germany.
Andreas F H
AFH
Pfeiffer
Krannert Institute of Cardiology, University of Indiana, Indianapolis, IN 46202, USA.
Loren J
LJ
Field
Departments of Biochemistry, Medicine (Endocrinology) and Obstetrics & Gynecology and Women's Health, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Maureen J
MJ
Charron
Mount Sinai School of Medicine, Icahn Medical Institute, Dept. of Oncological Sciences, 1425 Madison Avenue, New York, NY 10029, USA.
Zhen-Qiang
ZQ
Pan
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.|DZHK (German Center for Cardiovascular Research), partner site Munich Heart Alliance, 80802 Munich, Germany.
Stefan
S
Engelhardt
Institute of Pharmacology and Toxicology, Technische Universität München, Biedersteiner Straße 29, 80802 Munich, Germany.|DZHK (German Center for Cardiovascular Research), partner site Munich Heart Alliance, 80802 Munich, Germany.
Antonio
A
Sarikas
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D044842:Cullin Proteins / Q000235:genetics / Q000378:metabolism*; D044783:F-Box Proteins / Q000235:genetics / Q000378:metabolism; D057895:Haploinsufficiency; D007328:Insulin / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D046912:Multiprotein Complexes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
D001786:Blood Glucose; D002352:Carrier Proteins; D044842:Cullin Proteins; D044783:F-Box Proteins; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D044843:SKP Cullin F-Box Protein Ligases; D058570:TOR Serine-Threonine Kinases; C494817:Cul7 protein, mouse; C513332:Fbxw8 protein, mouse; C540494:RBX1 protein, mouse
2-DOG; 2-deoxy-d-((3)H)-glucose; ANOVA; CRL7; CUL7; Cell signaling; Cullin RING E3 ubiquitin ligase 7; Cullin7; E3 ubiquitin ligase; F-box/WD repeat-containing protein 8; FBXW8; GLUT4; HSP90; IGF-1; IRS; ITT; Insulin; MAPK; MEF; PI3K; Proteasome; RING; S6K; UPS; Ubiquitin; WT; analysis of variance; glucose transporter 4; heat shock protein 90; insulin receptor substrate; insulin tolerance test; insulin-like growth hormone 1; mTOR; mammalian target of rapamycin; mitogen-activated pathway kinase; mouse embryonic fibroblast; p70 S6 kinase; phosphoinositol-3 kinase; really interesting new gene; ubiquitin-proteasome-system; wild type