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  • The EMBO Journal (2001) 20, 1620 - 1629
  • doi:10.1093/emboj/20.7.1620

The Dictyostelium Bcr/Abr-related protein DRG regulates both Rac- and Rab-dependent pathways

Menno L.W. Knetsch1, Nicole Schäfers1, Heinz Horstmann2 and Dietmar J. Manstein1

  1. Department of Biophysics, Max-Planck-Institute for Medical Research, D-69120 Heidelberg, Germany
  2. Present address: Institute of Molecular and Cell Biology, National University of Singapore, 30 Medical Drive, Singapore 117609

Correspondence to:

Dietmar J. Manstein, E-mail: manstein@mpimf-heidelberg.mpg.de

Received 21 November 2000; Accepted 7 February 2001; Revised 7 February 2001

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.

  • Keywords:

    • actin,
    • contractile vacuole,
    • Dictyostelium,
    • RabD,
    • Rac