IDENTIFICATION OF SURROGATE AGONISTS FOR THE HUMAN FPRL-1 RECEPTOR BYAUTOCRINE SELECTION IN YEAST

We describe a procedure for isolating agonists for mammalian G protein -coupled receptors of unknown function, Human formyl peptide receptor like-1 (FPRL-1) receptor, originally identified as an orphan G protein -coupled receptor related to the formyl peptide receptor (FPR1), was e xpressed in Saccharomyces cells designed to couple receptor activation to histidine prototrophy. Selection for histidine prototrophs among t ransformants obtained with a plasmid-based library encoding random pep tides identified six different agonists, each of whose production yiel ded autocrine stimulation of the receptor expressed in yeast. A synthe tic version of each peptide promoted activation of FPRL-1 expressed in human embryonic kidney (HEK293) cells, and five of the peptides exhib ited significant selectivity for activation of FPRL-1 relative to FPR1 , One selective peptide was tested and found to mobilize calcium in is olated human neutrophils. This demonstrates that stimulation of FPRL-1 results in neutrophil activation and suggests that the receptor funct ions as a component of the inflammatory response, This autocrine selec tion protocol may be a generally applicable method for providing pharm acological tools to evaluate the physiological roles of the growing nu mber of mammalian orphan G protein-coupled receptors.