Role of IRS-1 Phosphorylation in IGF-1 and IL-4 Signaling in Breast Cancer
Abstract
Insulin-like growth factor-I (IGF-I) is a potent mitogen for breast cancer cells. Binding of IGF-I to its receptor results in activation of the receptor which then phosphorylates the adaptor protein insulin receptor substrate-1 (IRS-1). Our laboratory has shown that phosphorylation of IRS-1 by IGF-I caused enhanced ubiquitin dependent proteasomal degradation of IRS-1. In contrast, interleukin-4 (IL-4) which also phosphorylates IRS-1 does not enhance degradation of IRS-1. The goal of this project is to understand if phosphorylation of different residues on IRS-1 is responsible for the proliferative response mediated by IGF-I compared to the death signal mediated by IL-4. To identify the residues two-dimensional electrophoresis (2D PAGE) of IRS-1 was undertaken. The first task was to isolate phosphorylated P32-labeled IRS-1 which was successfully completed. Two-dimensional electrophoresis of IRS-1 which is a 180 kDa protein has encountered several technical difficulties. So far, IRS-1 has not been detected either by subjecting immunoprecipitated P32-labeled IRS-1 to 2D electrophoresis or immunoblotting lysates with IRS-1 antibody after 2D PAGE. In addition, we have not been able to see proteins above 100 kDa on 2D gels either by silver staining or radioisotope detection of P32 or S35 labeled lysates of MCF-7 cells.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2001
- Accession Number
- ADA396631
Entities
People
- Deepali Sachdev
Organizations
- University of Minnesota