title: A novel adenylyl cyclase detected in rapidly developing mutants of Dictyostelium.
abstract: Disruption of either the RDEA or REGA genes leads to rapid development in Dictyostelium. The RDEA gene product displays homology to certain H2-type phosphotransferases, while REGA encodes a cAMP phosphodiesterase with an associated response regulator. It has been proposed that RDEA activates REGA in a multistep phosphorelay. To test this proposal, we examined cAMP accumulation in rdeA and regA null mutants and found that these mutants show a pronounced accumulation of cAMP at the vegetative stage that is not observed in wild-type cells. This accumulation was due to a novel adenylyl cyclase and not to the known Dictyostelium adenylyl cyclases, aggregation stage adenylyl cyclase (ACA) or germination stage adenylyl cyclase (ACG), since it occurred in an acaA/rdeA double mutant and, unlike ACG, was inhibited by high osmolarity. The novel adenylyl cyclase was not regulated by G-proteins and was relatively insensitive to stimulation by Mn2+ ions. Addition of the cAMP phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX) permitted detection of the novel adenylyl cyclase activity in lysates of an acaA/acgA double mutant. The fact that disruption of the RDEA gene as well as inhibition of the REGA-phosphodiesterase by IBMX permitted detection of the novel AC activity supports the hypothesis that RDEA activates REGA.
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX13QU, United Kingdom.
authors.forename: H J
authors.initials: HJ
authors.lastname: Kim
authors.forename: W T
authors.initials: WT
authors.lastname: Chang
authors.forename: M
authors.initials: M
authors.lastname: Meima
authors.forename: J D
authors.initials: JD
authors.lastname: Gross
authors.forename: P
authors.initials: P
authors.lastname: Schaap
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004023:Dictyostelium / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D007527:Isoenzymes / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure; D015800:Protozoan Proteins
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D015800:Protozoan Proteins; C112741:RdeA protein, Dictyostelium; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; C112742:regA protein, Dictyostelium; D000262:Adenylyl Cyclases; D015056:1-Methyl-3-isobutylxanthine