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RhoGEF specificity mutants implicate RhoA as a target for Dbs transforming activity
Li Cheng1, Kent L Rossman, Gwendolyn M Mahon
1Department of Microbiology and Molecular Genetics, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark 07103-2714, USA.
Molecular and Cellular Biology
|September 7, 2002
Summary
Dbs, a RhoGEF, transforms cells by activating RhoA, not Cdc42. Specificity mutants reveal RhoA signaling is crucial for Dbs-mediated cell transformation.
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- Dbs is a Rho-specific guanine nucleotide exchange factor (RhoGEF) with transforming activity.
- RhoGEFs often lack substrate specificity, complicating the study of their functions.
- Dbs can activate both RhoA and Cdc42 GTPases.
Purpose of the Study:
- To determine the specific GTPase substrate responsible for Dbs-mediated cell transformation.
- To investigate the role of RhoA versus Cdc42 in the transforming activity of Dbs.
Main Methods:
- Utilized crystal structures of RhoGEFs bound to GTPases to predict specificity determinants.
- Created Dbs mutants to alter relative exchange activity for RhoA and Cdc42.
- Assessed Dbs-mediated transformation potential and activation of endogenous GTPases in NIH 3T3 cells.
Main Results:
- Dbs's transforming potential correlates with its exchange activity on RhoA, not Cdc42.
- Oncogenic Dbs activates endogenous RhoA but not Cdc42 in NIH 3T3 cells.
- Inhibition of RhoA activation blocks Dbs-mediated transformation.
Conclusions:
- Dbs transforms NIH 3T3 cells primarily through activation of RhoA.
- Specificity mutants of RhoGEFs are valuable tools for dissecting signaling pathways.
- This study implicates RhoA as the key mediator of Dbs-induced cell transformation.