Lysophosphatidic acid (LPA) is a major mitogen in serum that regulates an array of cellular processes related to pathogenesis of cancer and other human diseases. Despite the central role of LPA in controlling cell growth and other cellular activities, very little is understood about the signaling mechanisms of LPA. While protein tyrosine phosphorylation has been recognized as an important signaling mechanism of LPA and other agonists of G protein-coupled receptors, it remains largely unknown how activation of G-proteins leads to tyrosine phosphorylation. To address this important question, LPA-induced tyrosine phosphorylation of the epidermal growth factor receptor (EGFR) will be studied. Based on our preliminary observations and increasing evidence of redox-regulation in cell signaling, it is postulated that LPA transactivates the EGFR by decreasing EGF receptor phosphatase activity through a mechanism mediated by calcium and reactive oxygen species (ROS).
Three specific aims are proposed to critically evaluate key aspects of this hypothesis.
In Specific Aim I, the requirement for intrinsic EGFR tyrosine kinase activity will be assessed using kinase- defective EGFR and new specific inhibitors for the EGFR. Effects of decreasing protein tyrosine phosphatase activity toward EGFR will also be examined. Alternatively, a novel sensitive approach is proposed to determine whether LPA activates the EGFR kinase. TO further evaluate whether LPA-induced tyrosine phosphorylation is catalyzed by intrinsic EGF receptor kinase or by another cellular kinase, Specific Aim II proposes phosphopeptide mapping and mutagenesis experiments to analyze LPA-induced tyrosine phosphorylation sites on the EGFR.
In Specific Aim III, regulation of EGFR-dephosphorylating activity by LPA will be investigated both in vitro and in intact cells under conditions that redox-mediated changes can be detected, and the involvement of calcium and ROS will be evaluated. These studies not only will advance our understanding of signal transduction by LPA and G-proteins that control many cellular processes fundamental to the development of cancer and other human diseases, but also will stimulate further research in the emerging area of oxidative signaling.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
5R29CA077467-02
Application #
6137658
Study Section
Metabolic Pathology Study Section (MEP)
Program Officer
Spalholz, Barbara A
Project Start
1999-01-01
Project End
2003-12-31
Budget Start
2000-01-01
Budget End
2000-12-31
Support Year
2
Fiscal Year
2000
Total Cost
$98,594
Indirect Cost
Name
University of South Florida
Department
Biochemistry
Type
Schools of Medicine
DUNS #
City
Tampa
State
FL
Country
United States
Zip Code
33612
Ren, Yuan; Chen, Zhengming; Chen, Liwei et al. (2010) Critical role of Shp2 in tumor growth involving regulation of c-Myc. Genes Cancer 1:994-1007