GSBS Dissertations and Theses

Approval Date

8-11-2014

Document Type

Doctoral Dissertation

Academic Program

Cancer Biology

Department

Molecular, Cell and Cancer Biology Department

First Thesis Advisor

Leslie M. Shaw, PhD

Keywords

Signal Transduction, Insulin Receptor Substrate Proteins

Subjects

Dissertations, UMMS; Signal Transduction; Insulin Receptor Substrate Proteins

Abstract

The Insulin Receptor Substrate (IRS) proteins IRS-1 and IRS-2 are cytoplasmic adaptor proteins that organize and propagate intracellular signaling downstream of specific growth factor receptors, including the Insulin and Insulin-Like Growth Factor-1 Receptors (IR and IGF-1R, respectively). Despite sharing a high level of homology and the ability to stimulate Phosphotidylinositol-3-Kinase (PI3K) and Mitogen-Activated Protein Kinase (MAPK) signaling, IRS-1 and IRS-2 play distinct roles in mammary tumor progression. Specifically, IRS-1 promotes growth and proliferation, whereas IRS- 2 promotes motility, invasion, survival, aerobic glycolyis, and metastasis. To further understand the differences between IRS-1 and IRS-2, I investigated the mechanistic basis of IRS-2-mediated PI3K activation. I identified tyrosines in IRS-2 that mediate its recruitment and activation of PI3K in response to insulin and IGF-1 stimulation. Using a PI3K-binding deficient IRS-2 mutant, I demonstrated that IRS-2-dependent PI3K signaling promotes aerobic glycolysis through its ability to selectively regulate the phosphorylation of the Akt effector Glycogen Synthase Kinase-3β (Gsk-3β). I also performed a rigorous comparison of IRS-1 and IRS-2 signal transduction and their ability to regulate functions associated with tumor progression. These studies required the generation of a novel model system where IRS-1 and IRS-2 function could be compared in a genetically identical background. Using this model, I confirmed a role for IRS-1 in growth regulation and IRS-2 in tumor cell invasion, as well as expanded the understanding of differential IRS protein function by showing that IRS-2 more vi effectively promotes Akt activation. The model system I have established can be used for further characterization of IRS-1 and IRS-2-specific functions.

DOI

10.13028/M2BC82

Rights and Permissions

Copyright is held by the author, with all rights reserved.

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