title: Deletion of Nck1 attenuates hepatic ER stress signaling and improves glucose tolerance and insulin signaling in liver of obese mice.
abstract: Obesity has been shown to create stress in the endoplasmic reticulum (ER), and that initiates the activation of the unfolded protein response (UPR). This has been reported to cause insulin resistance in selective tissues through activation of the inositol-requiring enzyme 1α (IRE1α)-c-Jun NH(2)-terminal kinase (JNK) pathway, which results in the phosphorylation of the insulin receptor substrate-1 (IRS-1) at an inhibitory site and blocks insulin receptor signaling. In this study, we report that the Src homology domain-containing adaptor protein Nck1, previously shown to modulate the UPR, is of functional importance in obesity-induced ER stress signaling and inhibition of insulin actions. We have examined obese Nck1(-/-) and Nck1(+/+) mice for glucose tolerance, insulin sensitivity, and signaling as well as for ER stress markers and IRS-1 phosphorylation at Ser(307). Our findings show that obese Nck1-deficient mice display improved glucose disposal accompanied by enhanced insulin signaling in liver. This correlates with attenuated IRE1α and JNK activation and IRS-1 phosphorylation at Ser(307) compared with obese wild-type mice. Consistent with our in vivo data, we report that downregulation of Nck1 using siRNA in HepG2 cells results in decreased thapsigargin-induced IRE1α activation and signaling and IRS-1 phosphorylation at Ser(307), whereas it markedly enhances insulin signaling. Overall, in liver and in cultured cells, we show that depletion of Nck1 attenuates the UPR signal and its inhibitory action on insulin signaling. Taken all together, our findings implicate Nck1 in regulating the UPR, which secondary to obesity impairs glucose homeostasis and insulin actions.
authors.affiliation: Polypeptide Hormone Laboratory, Department of Experimental Medicine, Research Institute of the McGill University Health Centre, McGill University, 3640 University Street, Montreal, QC, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Latreille
authors.forename: Marie-Kristine
authors.initials: MK
authors.lastname: Laberge
authors.forename: Geneviève
authors.initials: G
authors.lastname: Bourret
authors.forename: Lama
authors.initials: L
authors.lastname: Yamani
authors.forename: Louise
authors.initials: L
authors.lastname: Larose
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000502:physiology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D004721:Endoplasmic Reticulum / Q000502:physiology*; D018149:Glucose Intolerance / Q000235:genetics* / Q000503:physiopathology*; D006003:Glycogen / Q000096:biosynthesis; D057809:HEK293 Cells; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000502:physiology*; D007333:Insulin Resistance / Q000235:genetics / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008820:Mice, Obese; D015513:Oncogene Proteins / Q000235:genetics* / Q000502:physiology*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics* / Q000502:physiology*; D056811:Unfolded Protein Response / Q000235:genetics / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001786:Blood Glucose; D007328:Insulin; D008565:Membrane Proteins; C078332:Nck protein; D015513:Oncogene Proteins; D006003:Glycogen; C486556:Ern2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases