title: Influx of extracellular Ca2+ is necessary for electrotaxis in Dictyostelium.
abstract: Intracellular free Ca2+ ([Ca2+](i)) is a pivotal signalling element in cell migration and is thought to be required for chemotaxis of Dictyostelium. Ca2+ signalling may also be important for electrotaxis. However this suggestion has been controversial. We show that electric fields direct Dictyostelium cells to migrate cathodally and increase [Ca2+](i) in Dictyostelium cells, as determined by Fluo-3 AM imaging and (45)Ca2+ uptake. Omission of extracellular Ca2+([Ca2+](e)) and incubation with EGTA abolished the electric-field-stimulated [Ca2+](i) rise and directional cell migration. This suggests a requirement for [Ca2+](e) in the electrotactic response. Deletion of iplA, a gene responsible for chemoattractant-induced [Ca2+](i) increase, had only a minor effect on the electric-field-induced [Ca2+](i) rise. Moreover, iplA-null Dictyostelium cells showed the same electrotactic response as wild-type cells. Therefore, iplA-independent Ca2+ influx is necessary for electrotactic cell migration. These results suggest that the [Ca2+](i) regulatory mechanisms induced by electric fields are different from those induced by cAMP and folic acid in Dictyostelium cells. Different roles of the iplA gene in chemoattractant-induced and electrically induced Ca2+ signalling, and different effects of [Ca2+](i) elevation on chemotaxis and electrotaxis indicate that the chemoattractant and electric cues activate distinctive initial signalling elements.
authors.affiliation: School of Medical Sciences, University of Aberdeen, Aberdeen, UK.
authors.forename: Lynne J
authors.initials: LJ
authors.lastname: Shanley
authors.forename: Petr
authors.initials: P
authors.lastname: Walczysko
authors.forename: Mary
authors.initials: M
authors.lastname: Bain
authors.forename: David J
authors.initials: DJ
authors.lastname: MacEwan
authors.forename: Min
authors.initials: M
authors.lastname: Zhao
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002465:Cell Movement; D002633:Chemotaxis / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D004023:Dictyostelium / Q000378:metabolism / Q000502:physiology*; D004574:Electromagnetic Fields; D005492:Folic Acid / Q000502:physiology; D009154:Mutation; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology
chemical_list: D015800:Protozoan Proteins; D005492:Folic Acid; D000242:Cyclic AMP; D002118:Calcium