Rho-like GTPases such as rhoA, rac1, and cdc42 play an essential role in growth factor-mediated changes in the actin cytoskeleton necessary for cell growth and motility. These GTPases are activated by guanine nucleotide exchange factors (GEFs) which promote the exchange of GDP for GTP, and are negatively regulated by GTPases activating proteins. The multifunctional Trio protein contains a rac1-specific GEF domain, a rhoA-specific GEF domain, a protein serine threonine kinase domain, and a number of auxiliary domains. Expression of the Trio rac1 GEF domain causes membrane ruffling and expression of the rhoA Trio GEF domain causes increased cell-matrix interactions via focal adhesion formation. Expression of the Trio rac1-specific GEF domain also causes anchorage independent growth of NIH 3T3 cells indicating that Trio is a potential proto-oncogene. Trio binds the focal adhesion-associated LAR transmembrane protein tyrosine phosphatase, suggesting that a Trio-LAR complex could also regulate protein tyrosine phosphorylation signaling. Given the central role of cell migration in metastasis, Trio may be particularly important in human cancer, as aberrant Trio expression may dysregulate cell growth and/or cell motility. Thus, we will study the Trio protein to understand how external signals are transmitted into the cell and how these signals lead to changes in cell growth and cell motility. The overall aim of this proposal is to test our hypothesis that Trio is an integrator/broadcaster of intracellular signal flow that coordinates multiple signals to regulate cytoskeletal changes associated with cell growth and cell motility.
The specific aims are: 1)to identify signaling events regulating Trio functions, 2) determine the role of the three Trio enzymatic domains within context of the entire Trio protein, and 3) to analyze Trio signal transduction via the isolation of Trio binding proteins. The health-relatedness of this project is to increase our understanding of the signaling pathways that regulate cell growth and motility. Malfunction of such mechanisms could result in cell transformation and/or tumor metastasis.
The aims will be accomplished by: i) identifying what upstream signals regulate Trio phosphorylation and localization, and determining how altered phosphorylation and/or localization affects Trio enzymatic activities; ii) determining what roles Trio plays in regulating cell morphology, motility and growth; and iii) identifying and characterizing Trio binding proteins, and determining the effect of the Trio-binding proteins on Trio signaling.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA075091-04
Application #
6350242
Study Section
Cellular Biology and Physiology Subcommittee 1 (CBY)
Project Start
1998-04-02
Project End
2002-01-31
Budget Start
2001-02-01
Budget End
2002-01-31
Support Year
4
Fiscal Year
2001
Total Cost
$244,943
Indirect Cost
Name
Dana-Farber Cancer Institute
Department
Type
DUNS #
149617367
City
Boston
State
MA
Country
United States
Zip Code
02215
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Medley, Quintus G; Buchbinder, Elizabeth G; Tachibana, Kouichi et al. (2003) Signaling between focal adhesion kinase and trio. J Biol Chem 278:13265-70
Seipel, K; O'Brien, S P; Iannotti, E et al. (2001) Tara, a novel F-actin binding protein, associates with the Trio guanine nucleotide exchange factor and regulates actin cytoskeletal organization. J Cell Sci 114:389-99
Medley, Q G; Serra-Pages, C; Iannotti, E et al. (2000) The trio guanine nucleotide exchange factor is a RhoA target. Binding of RhoA to the trio immunoglobulin-like domain. J Biol Chem 275:36116-23
Seipel, K; Medley, Q G; Kedersha, N L et al. (1999) Trio amino-terminal guanine nucleotide exchange factor domain expression promotes actin cytoskeleton reorganization, cell migration and anchorage-independent cell growth. J Cell Sci 112 ( Pt 12):1825-34