A secondary disruption of the dmpA gene encoding a large membrane protein allows aggregation defective Dictyostelium rasC- cells to form multicellular structures.
The disruption of the gene encoding the Dictyostelium Ras subfamily protein, RasC, results in a strain that does not aggregate and has defects in both cAMP signal relay and cAMP chemotaxis. Disruption of a second gene in the rasC(-) strain by Restriction Enzyme Mediated Integration produced cells that were capable of forming multicellular structures in plaques on bacterial lawns. The disrupted gene (dmpA) encoded a novel membrane protein that was designated Dmp1. Although the rasC(-)/dmpA(-) cells progressed through early development, they did not form aggregation streams on a plastic surface under submerged starvation conditions. Phosphorylation of PKB in response to cAMP, which is significantly reduced in rasC(-) cells, remained low in the rasC(-)/dmpA(-) cells. However, in spite of this low PKB phosphorylation, the rasC(-)/dmpA(-) cells underwent efficient chemotaxis to cAMP in a spatial gradient. Cyclic AMP accumulation, which was greatly reduced in the rasC(-) cells, was restored in the rasC(-)/dmpA(-) strain, but cAMP relay in these cells was not apparent. These data indicate that although the rasC(-)/dmpA(-) cells were capable of associating to form multicellular structures, normal aggregative cell signaling was clearly not restored. Disruption of the dmpA gene in a wild-type background resulted in cells that exhibited a slight defect in aggregation and a more substantial defect in late development. These results indicate that, in addition to the role played by Dmp1 in aggregation, it is also involved in late development.
Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
Meenal
M
Khosla
Paul
P
Kriebel
Carole A
CA
Parent
George B
GB
Spiegelman
Gerald
G
Weeks
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015139:Blotting, Southern; D002449:Cell Aggregation / Q000235:genetics; D002633:Chemotaxis / Q000235:genetics*; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics* / Q000502:physiology; D017353:Gene Deletion; D017125:Genes, Protozoan; D016153:Genes, Suppressor; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D010641:Phenotype; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000235:genetics; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology; D018631:ras Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics
D008565:Membrane Proteins; D015800:Protozoan Proteins; D000242:Cyclic AMP; D018631:ras Proteins