title: The Rac GEF ZizB regulates development, cell motility and cytokinesis in Dictyostelium.
abstract: Dock (dedicator of cytokinesis) proteins represent a family of guanine nucleotide exchange factors (GEFs) that include the well-studied Dock180 family and the poorly characterised zizimin family. Our current understanding of Dock180 function is that it regulates Rho small GTPases and thus has a role in a number of cell processes, including cell migration, development and division. Here, we use a tractable model for cell motility research, Dictyostelium discoideum, to help elucidate the role of the related zizimin proteins. We show that gene ablation of zizA causes no change in development, whereas ablation of zizB gives rise to an aberrant developmental morphology and a reduction in cell directionality and velocity, and altered cell shape. Fluorescently labelled ZizA protein associates with the microtubule-organising centre (MTOC), whereas ZizB is enriched in the cortex. Overexpression of ZizB also causes an increase in the number of filopodia and a partial inhibition of cytokinesis. Analysis of ZizB protein binding partners shows that it interacts with Rac1a and a range of actin-associated proteins. In conclusion, our work provides insight into the molecular and cellular functions of zizimin GEF proteins, which are shown to have a role in cell movement, filopodia formation and cytokinesis.
authors.affiliation: Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, UK.
authors.forename: Nicholl K
authors.initials: NK
authors.lastname: Pakes
authors.forename: Douwe M
authors.initials: DM
authors.lastname: Veltman
authors.forename: Francisco
authors.initials: F
authors.lastname: Rivero
authors.forename: Jamal
authors.initials: J
authors.lastname: Nasir
authors.forename: Robert
authors.initials: R
authors.lastname: Insall
authors.forename: Robin S B
authors.initials: RS
authors.lastname: Williams
mesh_terms: D000595:Amino Acid Sequence; D002465:Cell Movement; D048749:Cytokinesis; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D015800:Protozoan Proteins; D020744:rac GTP-Binding Proteins