Article

Association of insulin receptor substrate 1 (IRS-1) y895 with Grb-2 mediates the insulin signaling involved in IRS-1-deficient brown adipocyte mitogenesis.

Departamento de Bioquímica y Biología Molecular, Centro Mixto CSIC/UCM, Facultad de Farmacia, Universidad Complutense, 28040 Madrid, Spain.
Molecular and Cellular Biology (Impact Factor: 5.04). 05/2001; 21(7):2269-80. DOI: 10.1128/MCB.21.7.2269-2280.2001
Source: PubMed

ABSTRACT 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.

0 Bookmarks
 · 
87 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Insulin receptor substrate-1 (IRS1) is a key mediator of insulin signal transduction. Perturbations involving IRS1 complexes may lead to the development of insulin resistance and type 2 diabetes. Surprisingly, little is known about the proteins that interact with IRS1 in humans in health and disease conditions. We used a proteomic approach to assess IRS1 interaction partners in skeletal muscle from lean healthy controls (LC), obese insulin resistant non-diabetic controls (OC), and type 2 diabetic participants (T2D) before and after insulin infusion. We identified 113 novel endogenous IRS1 interaction partners, which represents the largest IRS1 interactome in humans and provides new targets for studies of IRS1 complexes in various diseases. Furthermore, we generated the 1st global picture of IRS1 interaction partners in LC, and how they differ in OC and T2D. Interestingly, dozens of proteins in OC and/or T2D exhibited increased associations with IRS1 compared to LC under the basal and/or insulin-stimulated conditions, revealing multiple new dysfunctional IRS1 pathways in OC and T2D. This novel abnormality, increased interaction of multiple proteins with IRS1 in obesity and type 2 diabetes in humans, provides new insights into the molecular mechanism of insulin resistance, and identifies new targets for type 2 diabetes drug development.
    Diabetes 02/2014; 63(6). DOI:10.2337/db13-1872 · 7.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study is to examine the effect of mutation on tyrosine kinase hINSR gene of DM Type 2 patients reduce the IRS- 1 activation by in silico analysis. Blood DNA of DM Type 2 patients from Saeful Anwar Hospital Malang were amplified and sequenced by specific primers of tyrosine kinase domain of hINSR gene. These gene sequences were converted to protein sequence by BLAST and the IRS-1 protein sequence is retrieved from NCBI database. Both of the protein sequence was aligned by using Bio edit version 5.0.6. The model of three dimension protein was predicted by SWISS MODEL webserver, and visualized the structure alteration by using Pymol 0.99rc6 and Hex 5.0, and then superimpose of the hINSR and IRS-1 interaction were examined by docking using Hex 5.0. The results showed that one substitution and one deletion of 8-3F patient exon-22 hINSR gene tyrosine kinase domain cause loss of four helixes and three coils structures on tyrosine kinase hINSR protein. Six-deletions and six-substitutions on same gene domain of DMK9 patient changed the two helixes became coil structure. The binding energy of hINSR tyrosine kinase with IRS-1 of normal is E= -494.67 kJ/mol, DMK9 patient is E= -458.4 kJ/mol, and 8-3F patient is E=-544.20 kJ/mol. The DMK9 patient prognosis has better physiological condition than 8-3F patient. Interaction between 8-3F of hINSR tyrosine kinase domain mutation and PTB domain IRS-1 is more spontaneous than DMK9, but both of them were reduced on IRS-1 activation respectively.
    Bioinformation 10/2013; 9(17):853-7. DOI:10.6026/97320630009853 · 0.50 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Obesity has reached epidemic proportions in the developed world. The progression from obesity to diabetes mellitus type 2, via metabolic syndrome, is recognised, and the significant associated increase in the risk of major human cancers acknowledged. We review the molecular basis of the involvement of morbidly high concentrations of endogenous or therapeutic insulin and of insulin-like growth factors in the progression from obesity to diabetes and finally to cancer. Epidemiological and biochemical studies establish the role of insulin and hyperinsulinaemia in cancer risk and progression. Insulin-like growth factors, IGF-1 and IGF-2, secreted by visceral or mammary adipose tissue have significant paracrine and endocrine effects. These effects can be exacerbated by increased steroid hormone production. Structural studies elucidate how each of the three ligands, insulin, IGF-1, and IGF-2, interacts differently with isoforms A and B of the insulin receptor and with type I IGF receptor and explain how these protagonists contribute to diabetes-associated cancer. The above should inform appropriate treatment of cancers that arise in obese individuals and in those with diabetes mellitus type 2. Novel drugs that target the insulin and insulin-like growth factor signal transduction pathways are in clinical trial and should be effective if appropriate biomarker-informed patient stratification is implemented.
    International Journal of Endocrinology 01/2013; 2013:632461. DOI:10.1155/2013/632461 · 1.52 Impact Factor

Full-text (4 Sources)

Download
50 Downloads
Available from
May 28, 2014