Phospholipase-C-Independent Inositol 1,4,5-Trisphosphate Formation in Dictyostelium Cells — Activation of a Plasma-Membrane-Bound Phosphatase by Receptor-Stimulated Ca2+ Influx

摘要: Dictyostelium cells have enzyme activities that generate the inositol polyphosphate Ins(1,4,5)P-3 from Ins(1,3,4,5,6)P-5 via intermediates Ins(1,3,4,5)P-4 and Ins(1,4,5,6)P-4. These could explain why with a deletion of single phospholipase C gene (plc(-) cells) possess nearly normal levels. In this study regulation subcellular localization was investigated. The performing different reaction steps to are probably due enzyme. Indications for previously shown similar Ca2+ dependencies various steps. Furthermore, mediating complete conversion co-purify after fractionation, solubilization, chromatography proteins. Subcellular fractionation studies demonstrate is localized mainly at inner face plasma membrane. activity not be stimulated in vitro by guanosine 5'-(3-thio)triphosphate, procedure known activate G-protein-coupled enzymes Dictyostelium. Still, plc(-) level increased significantly stimulation high concentrations extracellular ligand cAMP. This most likely influx because no increase detected absence Ca2+. results existence new receptor-controlled route formation independent C.