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The Dictyostelium Bcr/Abr-related protein DRG regulates both Rac- and Rab-dependent pathways
M L Knetsch1, N Schäfers, H Horstmann
1Department of Biophysics, Max-Planck-Institute for Medical Research, D-69120 Heidelberg, Germany.
The EMBO Journal
|April 4, 2001
Summary
Dictyostelium discoideum DdRacGap1 (DRG) regulates cell shape and division through its Rac1-dependent signaling and cytokinesis functions. DRG also controls the contractile vacuole system by modulating RabD GTPase activity.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Dictyostelium discoideum DdRacGap1 (DRG) is a multifunctional protein with both Rho-guanine nucleotide exchange factor (GEF) and Rho-GTPase activating protein (GAP) domains.
- This dual functionality is shared with mammalian proteins like Bcr and Abr, suggesting conserved roles in cellular regulation.
Purpose of the Study:
- To elucidate the physiological role of DRG in Dictyostelium discoideum.
- To characterize the enzymatic activities of DRG fragments and its in vivo functions.
Main Methods:
- In vitro characterization of recombinant DRG fragments' enzymatic activity.
- Creation and analysis of DRG-null Dictyostelium cells.
- In vivo studies using DRG-depleted cells and complementation assays with DRG or its fragments.
Main Results:
- DRG-GEF activity modulates F-actin dynamics and cAMP-induced F-actin formation via Rac1-dependent pathways.
- DRG's RacE-GAP activity is essential for proper cell cytokinesis.
- DRG-GAP activity accelerates RabD GTP hydrolysis and is required for RabD-dependent regulation of the contractile vacuole system, indicating specificity beyond Rho family GTPases.
Conclusions:
- DRG plays a critical role in regulating F-actin dynamics, cytokinesis, and the contractile vacuole system in Dictyostelium discoideum.
- The study highlights DRG's multifaceted regulatory functions involving both Rac1 and RabD GTPases.