The Dictyostelium Bcr/Abr-related protein DRG regulates both Rac- and Rab-dependent pathways.
Dictyostelium discoideum DdRacGap1 (DRG) contains both Rho-GEF and Rho-GAP domains, a feature it shares with mammalian Bcr and Abr. To elucidate the physiological role of this multifunctional protein, we characterized the enzymatic activity of recombinant DRG fragments in vitro, created DRG-null cells, and studied the function of the protein in vivo by analysing the phenotypic changes displayed by DRG-depleted cells and DRG-null cells complemented with DRG or DRG fragments. Our results show that DRG-GEF modulates F-actin dynamics and cAMP-induced F-actin formation via Rac1-dependent signalling pathways. DRG's RacE-GAP activity is required for proper cytokinesis to occur. Additionally, we provide evidence that the specificity of DRG is not limited to members of the Rho family of small GTPases. A recombinant DRG-GAP accelerates the GTP hydrolysis of RabD 30-fold in vitro and our complementation studies show that DRG-GAP activity is required for the RabD-dependent regulation of the contractile vacuole system in Dictyostelium.
Knetsch
M L
ML
Department of Biophysics, Max-Planck-Institute for Medical Research, D-69120 Heidelberg, Germany.
Schäfers
N
N
Horstmann
H
H
Manstein
D J
DJ
D000818:Animals; D004023:Dictyostelium; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011505:Protein-Tyrosine Kinases; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051562:Proto-Oncogene Proteins c-bcr; D064067:Rho Guanine Nucleotide Exchange Factors; D015398:Signal Transduction; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D011506:Proteins; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; C085379:rho GTPase-activating protein; D011505:Protein-Tyrosine Kinases; D051562:Proto-Oncogene Proteins c-bcr; D020691:rab GTP-Binding Proteins; D020744:rac GTP-Binding Proteins