Lysophospholipid receptor-mediated calcium signaling in human keratinocytes.

The lysophospholipids, sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA), stimulate chemotaxis and induce differentiation of human keratinocytes. As Ca(2+) plays an important role in keratinocyte differentiation, we studied Ca(2+) signaling by S1P and LPA in these cells, known to express mRNA transcripts of the S1P(1-5) and LPA(1-3) receptors, and the receptor subtypes involved in this process. S1P and LPA caused transient increases in intracellular free Ca(2+) concentration (Ca(2+)), with pEC(50) values of 8.5+/-0.11 and 7.5+/-0.23, respectively. The Ca(2+) increases are apparently mediated by stimulation of phospholipase C and involve Ca(2+) mobilization from thapsigargin-sensitive stores and subsequent Ca(2+) influx. The LPA-induced Ca(2+) increases were not inhibited by the LPA(1/3) receptor antagonist, dioctanoylglycerol pyrophosphate. The S1P-induced Ca(2+) increases were largely inhibited by the putative S1P(3) antagonist, BML-241, and the S1P(1/3) antagonist, VPC23019. The S1P(1)-specific agonist, SEW2871, did not increase Ca(2+) but stimulated chemotaxis of keratinocytes, which was fully blocked by S1P(1) antisense oligonucleotides. The data indicate that LPA and S1P potently increase Ca(2+) in human keratinocytes and that the effect of LPA is mediated by LPA(2), whereas that of S1P is mediated at least to a large part by S1P(3). The S1P(1) receptor, without stimulating Ca(2+) increases, mediates chemotaxis of keratinocytes.