Detection of calmodulin-binding proteins and calmodulin-dependent phosphorylation linked to calmodulin-dependent chemotaxis to folic and cAMP in Dictyostelium.
Calmodulin (CaM) antagonists, trifluoperazine (TFP) or calmidazolium (R24571), dose-dependently inhibited cAMP and folic acid (FA) chemotaxis in Dictyostelium. Developing, starved, and refed cells were compared to determine if certain CaM-binding proteins (CaMBPs) and CaM-dependent phosphorylation events could be identified as potential downstream effectors. Recombinant CaM ([35S]VU-1-CaM) gel overlays coupled with cell fractionation revealed at least three dozen Ca(2+)-dependent and around 12 Ca(2+)-independent CaMBPs in Dictyostelium. The CaMBPs associated with early development were also found in experimentally starved cells (cAMP chemotaxis), but were different for the CaMBP population linked to growth-phase cells (FA chemotaxis). Probing Western blots with phosphoserine antibodies revealed several phosphoprotein bands that displayed increases when cAMP-responsive cells were treated with TFP. In FA-responsive cells, several but distinct phosphoproteins decreased when treated with TFP. These data show that unique CaMBPs are present in growing, FA-chemosensitive cells vs. starved cAMP-chemoresponsive cells that may be important for mediating CaM-dependent events during chemotaxis.
Gauthier
M L
ML
Department of Zoology, University of Toronto at Mississauga, L5L 1C6, Mississauga, ON, Canada.
O'Day
D H
DH
D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D002148:Calmodulin-Binding Proteins / Q000032:analysis*; D002465:Cell Movement; D002633:Chemotaxis / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology*; D004023:Dictyostelium / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005492:Folic Acid / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry; D014268:Trifluoperazine / Q000494:pharmacology
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D010768:Phosphoserine; D014268:Trifluoperazine; C031938:calmidazolium; D005492:Folic Acid; D000242:Cyclic AMP