title: Regulation of Dictyostelium morphogenesis by RapGAP3.
abstract: Rap1 is a key regulator of cell adhesion and cell motility in Dictyostelium. Here, we identify a Rap1-specific GAP protein (RapGAP3) and provide evidence that Rap1 signaling regulates cell-cell adhesion and cell migration within the multicellular organism. RapGAP3 mediates the deactivation of Rap1 at the late mound stage of development and plays an important role in regulating cell sorting during apical tip formation, when the anterior-posterior axis of the organism is formed, by controlling cell-cell adhesion and cell migration. The loss of RapGAP3 results in a severely altered morphogenesis of the multicellular organism at the late mound stage. Direct measurement of cell motility within the mound shows that rapGAP3(-) cells have a reduced speed of movement and, compared to wild-type cells, have a reduced motility towards the apex. rapGAP3(-) cells exhibit some increased EDTA/EGTA sensitive cell-cell adhesion at the late mound stage. RapGAP3 transiently and rapidly translocates to the cell cortex in response to chemoattractant stimulation, which is dependent on F-actin polymerization. We suggest that the altered morphogenesis and the cell-sorting defect of rapGAP3(-) cells may result in reduced directional movement of the mutant cells to the apex of the mound.
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, Center for Molecular Genetics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0380, USA.
authors.forename: Taeck J
authors.initials: TJ
authors.lastname: Jeon
authors.forename: Susan
authors.initials: S
authors.lastname: Lee
authors.forename: Gerald
authors.initials: G
authors.lastname: Weeks
authors.forename: Richard A
authors.initials: RA
authors.lastname: Firtel
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D004023:Dictyostelium / Q000254:growth & development / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000502:physiology*; D055786:Gene Knockout Techniques; D009024:Morphogenesis / Q000502:physiology; D009154:Mutation; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D020690:GTPase-Activating Proteins; D015800:Protozoan Proteins; D020827:rap1 GTP-Binding Proteins