title: On the role of calcium during chemotactic signalling and differentiation of the cellular slime mould Dictyostelium discoideum.
abstract: Transient cytosolic calcium elevations are required for chemotaxis and differentiation of Dictyostelium discoideum since Ca2+ chelating buffers introduced into the cells by scrape loading inhibited motility as well as orientation in a Ca2+ specific manner. Ca2+ changes are provided either by intrinsic cytosolic Ca2+ oscillations that can be determined as periodic Ca2+ efflux, or by receptor-mediated Ca2+ liberation from the InsP3-sensitive store and Ca2+ influx. Cytosolic Ca2+ homeostasis as well as oscillations seem to be regulated by two different Ca2+ stores, the acidosomes and the InsP3-sensitive store, both of which are dependent on Ca2+ pumps and V-type H+ ATPases. Ca2+ transients are sensed by calmodulin-binding proteins. The latter have been detected in Dictyostelium by 125I-calmodulin labeling. A calmodulin-dependent protein phosphatase, calcineurin A, was cloned, sequenced, purified and characterized biochemically. Overproduction of calcineurin A as well as antisense constructs will help to the elucidation of its function in signal transduction. Surprisingly, protein synthesis is also controlled by Ca2+/calmodulin. An integral ribosomal protein of the 60S subunit, L19, proved to be a calmodulin-binding protein and calmodulin antagonists of different classes, inhibited in vitro translation of Dictyostelium and wheat germ extracts.
authors: Faculty of Biology, University of Konstanz, Germany.
authors: D
authors: D
authors: Malchow
authors: R
authors: R
authors: Mutzel
authors: C
authors: C
authors: Schlatterer
mesh_terms: D000818:Animals; D019703:Calcineurin; D002118:Calcium / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D002633:Chemotaxis / Q000502:physiology; D004023:Dictyostelium / Q000254:growth & development / Q000378:metabolism*; D005656:Fungal Proteins / Q000096:biosynthesis; D007424:Intracellular Fluid / Q000378:metabolism; D017136:Ion Transport / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D015800:Protozoan Proteins / Q000096:biosynthesis; D015398:Signal Transduction / Q000502:physiology
chemical_list: D002148:Calmodulin-Binding Proteins; D005656:Fungal Proteins; D015800:Protozoan Proteins; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002118:Calcium