Journal of Biosciences, Dec, 2007, Vol.32(3), p.1281(9)
Byline: Ralph H. Schaloske (1), Dagmar Blaesius (2), Christina Schlatterer (3), Daniel F. Lusche (4) Keywords: Arachidonic acid; chemotaxis; fatty acids; iplA Abstract: 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 (PIP.sub.3), Ca.sup.2+ 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 Ca.sup.2+ concentration by causing the release of Ca.sup.2+ from intracellular stores and activating influx of extracellular Ca.sup.2+. 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. Ca.sup.2+ played an important role in AA chemotaxis of wild-type Ax2 as ethyleneglycolbis(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)P.sub.3-receptor had been knocked out, chemotaxis was only slightly affected by EGTA. Chemotaxis in the presence of extracellular Ca.sup.2+ 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. Author Affiliation: (1) Department of Chemistry and Biochemistry, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0601, USA (2) Pharmaceutical Institute, Universty of Tuebingen, Morgenstelle 8, 72076, Tuebingen, Germany (3) Department of Biology, University of Konstanz, Universitaetsstr.10, 78457, Konstanz, Germany (4) W M Keck Dynamic Image Analysis Facility, Department of Biological Sciences, The University of Iowa, Iowa City, IA, 52242, USA Article History: Registration Date: 06/05/2007 Received Date: 02/05/2007 Accepted Date: 01/09/2007 Online Date: 07/05/2008 Article note: These authors contributed equally to this work. This work was carried out at the University of Konstanz, Department of Biology, Universitaetstr.10, 78457 Konstanz, Germany.
Arachidonic Acid -- Health Aspects ; Arachidonic Acid -- Research ; Chemotaxis -- Health Aspects ; Chemotaxis -- Research ; Dictyostelium -- Health Aspects ; Dictyostelium -- Research