The effect of the disruption of a gene encoding a PI4 kinase on the developmental defect exhibited by Dictyostelium rasC(-) cells.
The disruption of the gene encoding the Dictyostelium Ras subfamily protein, RasC results in a strain that fails to aggregate with defects in both cAMP signal relay and chemotaxis. Restriction enzyme mediated integration disruption of a second gene in the rasC(-) strain resulted in cells that were capable of forming multicellular structures in plaques on bacterial lawns. The disrupted gene, designated pikD(1), encodes a member of the phosphatidyl-inositol-4-kinase beta subfamily. Although the rasC(-)/pikD(1) cells were capable of progressing through early development, when starved on a plastic surface under submerged conditions, they did not form aggregation streams or exhibit pulsatile motion. The rasC(-)/pikD(1) cells were extremely efficient in their ability to chemotax to cAMP in a spatial gradient, although the reduced phosphorylation of PKB in response to cAMP observed in rasC(-) cells, was unchanged. In addition, the activation of adenylyl cyclase, which was greatly reduced in the rasC(-) cells, was only minimally increased in the rasC(-)/pikD(1) strain. Thus, although the rasC(-)/pikD(-) cells were capable of associating to form multicellular structures, normal cell signaling was clearly not restored. The disruption of the pikD gene in a wild type background resulted in a strain that was delayed in aggregation and formed large aggregation streams, when starved on a plastic surface under submerged conditions. This strain also exhibited a slight defect in terminal development. In conclusion, disruption of the pikD gene in a rasC(-) strain resulted in cells that were capable of forming multicellular structures, but which did so in the absence of normal signaling and aggregation stream formation.
Khosla
Meenal
M
Department of Microbiology and Immunology, University of British Columbia, , 300-6174 University Boulevard, Vancouver, BC, Canada V6T 1Z3.
Spiegelman
George B
GB
Weeks
Gerald
G
D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000235:genetics; D002449:Cell Aggregation / Q000235:genetics; D002633:Chemotaxis; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology; D016054:DNA, Protozoan; D004023:Dictyostelium / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D004789:Enzyme Activation; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D017125:Genes, Protozoan; D011905:Genes, ras; D007700:Kinetics; D016254:Mutagenesis, Insertional; D015398:Signal Transduction; D013217:Starvation
D016054:DNA, Protozoan; C018892:2'-deoxy cyclic AMP; D000242:Cyclic AMP; D019870:1-Phosphatidylinositol 4-Kinase; D000262:Adenylyl Cyclases