EDG-2 VZG-1 COUPLES TO THE YEAST PHEROMONE RESPONSE PATHWAY SELECTIVELY IN RESPONSE TO LYSOPHOSPHATIDIC ACID/

We have functionally expressed the human cDNA encoding the putative ly sophosphatidic acid (LPA) receptor Edg-2 (Vzg-1) in Saccharomyces cere visiae in an attempt to determine the agonist specificity of this G-pr otein-coupled receptor. LPA activated the pheromone response pathway i n S. cerevisiae expressing Edg-2 in a time- and dose-dependent manner as determined by induction of a pheromone-responsive FUS1::lacZ report er gene, LPA-mediated activation of the pheromone response pathway was dependent on mutational inactivation of the SST2 gene, the GTPase-act ivating protein for the yeast G(alpha) protein (the GPA1 gene product) , This indicates that, in sst2 Delta yeast cells, Edg-2 can efficientl y couple to the yeast heterotrimeric G-protein in response to LPA and activate the yeast mitogen-activated protein kinase pathway, The Edg-2 receptor showed a high degree of specificity for LPA; other lyso-glyc erophospholipids, sphingosine 1-phosphate, and diacyl-glycerophospholi pids did not activate FUS1::lacZ. LPA analogs including a cyclic phosp hoester form and ether-linked forms of LPA activated FUS1::lacZ, altho ugh fatty acid chains of 6 and 10 carbons did not activate FUS1::lacZ, suggesting a role for the side chain in ligand binding or receptor ac tivation, These results indicate that Edg-2 encodes a highly specific LPA receptor.