EXCEEDTHE SPACE PROVIDED. Chemoattractants and chemokines play a critical role in host defense against invading pathogens. Their ability to attract leukocytes to sites of infection and inflammation and stimulate the generation of superoxide radicals and the release degradative enzymes is vital to human health. On the contrary, these life saving responses, when not properly regulated, can also lead to numerous pathological conditions. Following ischaemic periods in tissues, such as those seen with myocardial thrombosis or stroke, inappropriate leukocyte activation can result in significant tissue damgae. Rheumatoid arthritis and inflammatory bowel disease are also intimately associated with excess leukocyte activation. Chemoattractants exert their effects on leukocytes by binding 1:0 heptahelical G protein-coupled receptors (GPCRs). For the proposed studies in this application, we will utilise the well characterized N-formyl peptide receptor (FPR). The goal of the proposed studies is to define at the molecular level the mechanismsinvolved in the regulation of leukocyte GPCR activation. Desensitization is the process of diminishing the magnitude of receptor-mediated signal transduction processes upon chronic or repeated agonist stimulation. The two major processing events of chemoattractant G protein-coupled receptors consist of receptor/G-protein uncoupling and receptor internalization. We have previously demonstrated that phosphorylation within the carboxy terminus of the FPR plays a critical role in these processes. However, it remains unclear how receptor phosphorylation leads to these events. Our evidence suggests that distinct, and therefore at least two discernable mechanismsare responsible for receptor desensitization and internalization. Our goals include the evaluation of the interaction of cytosolic components with the phosphorylated carboxy-terminus of the FPR. We will determine the role(s) of arrestins and other proteins in chemoattractant receptor desensitization and internalization. We will utilize FPR mutants of the intracellular domains, and in particular the phosphorylated carboxy-terminus, expressed in myeloid cell lines for functional analyses. We will also explore for novel proteins which interact with the FPR to facilitate these processes. Infoimation obtained from these studies will extend our understanding of the regulation of signal transduction pathways initiated by chemoattractant receptors. The long term goals are to develop therapeutic means to control leukocyte activity and prevent the host damage resulting from excessive leukocyte activation. PERFORMANCE SITE ========================================Section End===========================================
