Association of Insulin Receptor Substrate 1 (IRS-1) Y895 with Grb-2 Mediates the Insulin Signaling Involved in IRS-1-Deficient Brown Adipocyte Mitogenesis
| Autor: | Angela M. Valverde, Morris F. White, Sebastian Pons, Alberto Alvarez, Manuel Benito, C. Mur, C R Kahn |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
MAPK/ERK pathway
medicine.medical_specialty Insulin Receptor Substrate Proteins medicine.medical_treatment Mitosis environment and public health Mice chemistry.chemical_compound Adipose Tissue Brown Internal medicine Insulin receptor substrate Adipocytes medicine Animals Insulin Cell Growth and Development Molecular Biology Cells Cultured Adaptor Proteins Signal Transducing GRB2 Adaptor Protein biology Kinase Proteins Tyrosine phosphorylation Cell Biology Phosphoproteins IRS1 Cell biology Insulin receptor Endocrinology chemistry biology.protein Gene Deletion hormones hormone substitutes and hormone antagonists Signal Transduction |
| Zdroj: | Molecular and Cellular Biology. 21:2269-2280 |
| ISSN: | 1098-5549 |
| Popis: | We have recently generated immortalized fetal brown adipocyte cell lines from insulin receptor substrate 1 (IRS-1) knockout mice and demonstrated an impairment in insulin-induced lipid synthesis as compared to wild-type cell lines. In this study, we investigated the consequences of IRS-1 deficiency on mitogenesis in response to insulin. The lack of IRS-1 resulted in the inability of insulin-stimulated IRS-1-deficient brown adipocytes to increase DNA synthesis and enter into S/G2/M phases of the cell cycle. These cells showed a severe impairment in activating mitogen-activated protein kinase kinase (MEK1/2) and p42-p44 mitogen-activated protein kinase (MAPK) upon insulin stimulation. IRS-1-deficient cells also lacked tyrosine phosphorylation of SHC and showed no SHC–Grb-2 association in response to insulin. The mitogenic response to insulin could be partially restored by enhancing IRS-2 tyrosine phosphorylation and its association with Grb-2 by inhibition of phosphatidylinositol 3-kinase activity through a feedback mechanism. Reconstitution of IRS-1-deficient brown adipocytes with wild-type IRS-1 restored insulin-induced IRS-1 and SHC tyrosine phosphorylation and IRS-1–Grb-2, IRS-1–SHC, and SHC–Grb-2 associations, leading to the activation of MAPK and enhancement of DNA synthesis. Reconstitution of IRS-1-deficient brown adipocytes with the IRS-1 mutant Tyr895Phe, which lacks IRS-1–Grb-2 binding, restored SHC–IRS-1 association and SHC–Grb-2 association. However, the lack of IRS-1–Grb-2 association impaired MAPK activation and DNA synthesis in insulin-stimulated mutant cells. These data provide strong evidence for an essential role of IRS-1 and its direct association with Grb-2 in the insulin signaling pathway leading to MAPK activation and mitogenesis in brown adipocytes. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|