title: Dictyostelium Dock180-related RacGEFs regulate the actin cytoskeleton during cell motility.
abstract: Cell motility of amoeboid cells is mediated by localized F-actin polymerization that drives the extension of membrane protrusions to promote forward movements. We show that deletion of either of two members of the Dictyostelium Dock180 family of RacGEFs, DockA and DockD, causes decreased speed of chemotaxing cells. The phenotype is enhanced in the double mutant and expression of DockA or DockD complements the reduced speed of randomly moving DockD null cells' phenotype, suggesting that DockA and DockD are likely to act redundantly and to have similar functions in regulating cell movement. In this regard, we find that overexpressing DockD causes increased cell speed by enhancing F-actin polymerization at the sites of pseudopod extension. DockD localizes to the cell cortex upon chemoattractant stimulation and at the leading edge of migrating cells and this localization is dependent on PI3K activity, suggesting that DockD might be part of the pathway that links PtdIns(3,4,5)P(3) production to F-actin polymerization. Using a proteomic approach, we found that DdELMO1 is associated with DockD and that Rac1A and RacC are possible in vivo DockD substrates. In conclusion, our work provides a further understanding of how cell motility is controlled and provides evidence that the molecular mechanism underlying Dock180-related protein function is evolutionarily conserved.
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0380, USA.
authors.forename: Alessia
authors.initials: A
authors.lastname: Para
authors.forename: Miriam
authors.initials: M
authors.lastname: Krischke
authors.forename: Sylvain
authors.initials: S
authors.lastname: Merlot
authors.forename: Zhouxin
authors.initials: Z
authors.lastname: Shen
authors.forename: Michael
authors.initials: M
authors.lastname: Oberholzer
authors.forename: Susan
authors.initials: S
authors.lastname: Lee
authors.forename: Steven
authors.initials: S
authors.lastname: Briggs
authors.forename: Richard A
authors.initials: RA
authors.lastname: Firtel
mesh_terms: D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D002630:Chemotactic Factors / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D006801:Humans; D046912:Multiprotein Complexes / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002630:Chemotactic Factors; C465214:ELMO1 protein, human; D046912:Multiprotein Complexes; D015800:Protozoan Proteins; D020744:rac GTP-Binding Proteins