Arachidonic acid is a chemoattractant for Dictyostelium discoideum cells.
Cyclic AMP (cAMP)is a natural chemoattractant of the social amoeba Dictyostelium discoideum. It is detected by cell surface cAMP receptors. Besides a signalling cascade involving phosphatidylinositol 3,4,5-trisphosphate (PIP3), Ca2+ signalling has been shown to have a major role in chemotaxis. Previously, we have shown that arachidonic acid (AA) induces an increase in the cytosolic Ca2+ concentration by causing the release of Ca2+ from intracellular stores and activating influx of extracellular Ca2+. Here we report that AA is a chemoattractant for D. discoideum cells differentiated for 8-9 h. Motility towards a glass capillary filled with an AA solution was dose-dependent and qualitatively comparable to cAMP-induced chemotaxis. Ca2+ played an important role in AA chemotaxis of wild-type Ax2 as ethyleneglycol-bis(b-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA) added to the extracellular buffer strongly inhibited motility. In the HM1049 mutant whose iplA gene encoding a putative Ins(1,4,5)P3 -receptor had been knocked out, chemotaxis was only slightly affected by EGTA. Chemotaxis in the presence of extracellular Ca2+ was similar in both strains. Unlike cAMP, addition of AA to a cell suspension did not change cAMP or cGMP levels. A model for AA chemotaxis based on the findings in this and previous work is presented.
Schaloske
Ralph H
RH
Department of Chemistry and Biochemistry, University of California at San Diego,9500 Gilman Drive, La Jolla, CA 92093-0601, USA.
Blaesius
Dagmar
D
Schlatterer
Christina
C
Lusche
Daniel F
DF
D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002633:Chemotaxis / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology* / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D009154:Mutation
D016718:Arachidonic Acid; D004533:Egtazic Acid; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium