Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10815980 | Cellular Signalling | 2007 | 8 Pages |
Abstract
Asb-4 is a gene that is specifically expressed in the hypothalamic energy homeostasis-associated areas and is down-regulated in the arcuate nucleus of fasted Sprague Dawley and obese Zucker rats. It has two functional domains, the ankyrin repeat and the SOCS box. The function of Asb-4 is unclear. We used yeast two hybridization to search for protein(s) that interact with Asb-4. With Asb-4 minus its SOCS box (Asb-4/Îsb) as a bait, we screened mouse testis and arcuate nucleus cDNA libraries and identified G-protein pathway suppressor 1 (GPS1, also known as CSN1) as an Asb-4 interacting protein. GPS1 co-immunoprecipitated with Asb-4 both in vitro and in human HEK293 cells. When Asb-4 and GPS1 were co-transfected into HEK293 cells, expression of Asb-4 reduced the protein level of GPS1. Deletion of the SOCS box (Asb4/Îsb) did not abolish the inhibitory effect of Asb-4 on GPS1, indicating that the SOCS box was not needed for its inhibitory effect. In NIH 3T3 L1 cells, expression of GPS1 enhanced c-Jun NH2-terminal kinase (JNK) activity. Co-expression of Asb-4 with GPS1 inhibited JNK activity. Treatment of the cells with insulin (20Â nM) stimulated JNK activity. Expression of GPS1 potentiated the stimulatory effect of insulin, whereas co-expression of Asb-4 along with GPS1 inhibited JNK activity. In HEK293 cells expression of GPS1 elevated phosphorylation of insulin receptor substrate 1 (IRS-1) at serine307, co-expression of Asb-4 with GPS1 reduced the IRS-1ser307 phosphorylation. The present study demonstrates that Asb-4 interacts with GPS1 and inhibits JNK activity.
Keywords
IRS-1Gps1c-Jun NH2-terminal kinase (JNK)QDOSOCSSOCS1c-Jun NH2-terminal kinasepro-opiomelanocortinSDSPAGEJnkeGFPPOMCNPYRT-PCRpolyacrylamide gel electrophoresisinsulin receptor substrate 1sodium dodecyl sulfatesuppressor of cytokine signalingHEK293 cellhuman embryonic kidney 293 cellCo-IPArcarcuate nucleusCo-Immunoprecipitationreverse transcription polymerase chain reactionenhanced green fluorescent proteinkilodaltonsNeuropeptide Y
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Authors
Ji-Yao Li, Biao-Xin Chai, Weizhen Zhang, Yi-Qing Liu, John B. Ammori, Michael W. Mulholland,