The N-formyl peptide chemoattractant receptor (fMLF-R) is a glycoprotein that mediates the directed migration of polymorphonuclear neutrophils during inflammation. The fMLF-R shares many features with the superfamily of rhodopsin-type receptors possessing seven transmembrane domains and it mediates its cellular effects through a pertussis toxin sensitive G- binding protein. The N-formylated peptides (N-formyl-met-leu-phe) that bind the fMLF-R are thought to be derived from bacterial protein degradation and possibly from mitochondrial proteins upon tissue damage. The binding of N-formylated peptides mediate a variety of cellular and biochemical responses in neutrophils and macrophages including bacteriocidal superoxide radical production, release of proteolytic enzymes from intracellular granules, aggregation and phagocytosis. The infiltration of neutrophils and macrophages into tissues are thought to play an important role in the pathogenesis of many diseases including adult respiratory distress syndrome (ARDS), rheumatoid arthritis, myocardial reperfusion injury, and inflammatory bowel disease. Chemotactic factors, such as fMLF, likely play a role in these disease processes. in addition to myeloid cells, the fMLF-R has been identified on non-myeloid cells such as liver parenchyma, cells of the central nervous system, and lung epithelium. This would strongly suggest that the biological functions mediated by fMLF are likely to be even more pleiotropic and important that originally assumed and that it has other functions than directing the migration of leukocytes. The broad long term objective of this proposal are to examine the expression and regulation of the N-formyl peptide receptor (fMLF-R) and thereby modulate its role during inflammation such that tissue damage by neutrophils can be minimized. Molecular knowledge of the regulation and functional aspects of the fMLF-R are paramount in achieving this goal. Our immediate objectives are to: l) examine the transcriptional and translational regulation of the fMLF-R using U937 cells as a model for neutrophils using reporter gene constructs and cytokines; 2) using ligand binding studies examine the biology of the fMLF-R in non-myeloid cells; 3) initiate studies into the biological functions mediated by the fMLF-R on tissue cells by examining the expression of adhesion molecules involved in neutrophil migration; and 4) explore the identity, origin, and potential function of a family of fMLF-R homologues by sequencing, transfection, and ligand binding studies.
