title: Identification of darlin, a Dictyostelium protein with Armadillo-like repeats that binds to small GTPases and is important for the proper aggregation of developing cells.
abstract: We purified from Dictyostelium lysates an 88-kDa protein that bound to a subset of small GTPases, including racE, racC, cdc42Hs, and TC4ran, but did not bind to R-ras or rabB. Cloning of the gene encoding this 88-kDa protein revealed that it contained multiple armadillo-like repeats most closely related to the mammalian GTP exchange factor smgGDS. We named this protein darlin (Dictyostelium armadillo-like protein). Disruption of the gene encoding darlin demonstrated that this protein is not essential for cytokinesis, pinocytosis, phagocytosis, or development. However, the ability of darlin null cells to aggregate in response to starvation is severely affected. When starved under liquid medium, the mutant cells were unable to form aggregation centers and streams, possibly because of a defect in cAMP relay signaling. This defect was not due to an inability of the darlin mutants to activate adenylate cyclase in response to G protein stimulation. These results suggest that the darlin protein is involved in a signaling pathway that may modulate the chemotactic response during early development.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Vithalani
authors.forename: C A
authors.initials: CA
authors.lastname: Parent
authors.forename: E M
authors.initials: EM
authors.lastname: Thorn
authors.forename: M
authors.initials: M
authors.lastname: Penn
authors.forename: D A
authors.initials: DA
authors.lastname: Larochelle
authors.forename: P N
authors.initials: PN
authors.lastname: Devreotes
authors.forename: A
authors.initials: A
authors.lastname: De Lozanne
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051186:Armadillo Domain Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002417:Cattle; D003001:Cloning, Molecular; D016054:DNA, Protozoan; D004023:Dictyostelium / Q000235:genetics* / Q000502:physiology; D029721:Drosophila Proteins; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators
chemical_list: D051186:Armadillo Domain Proteins; D002352:Carrier Proteins; D016054:DNA, Protozoan; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; D019476:Insect Proteins; D015800:Protozoan Proteins; D015534:Trans-Activators; C116560:darlin protein, Dictyostelium; D020558:GTP Phosphohydrolases