The goal of the project is to molecularly clone and characterize novel chemokine receptors in lymphocytes. Chemokines are members of a family of more than thirty human cytokines whose best described activities are as chemotactic factors for leukocytes. Our laboratory has focused on chemokines that specifically target activated lymphocytes. As part of studies of the actions of chemokines on lymphocyte physiology, we have screened lines of human tumor infiltrating lymphocytes (TIL) to identify novel chemokine receptors. These experiments are of particular relevance to AIDS given the recent discoveries that chemokine receptors function as obligate co-receptors for HIV-1 entry. Using the polymerse chain reaction with pools of degenerate primers we have identified two novel seven transmembrane domain receptors designated STRL22 and STRL33 that are related by sequence to known chemokine receptors. cDNA clones isolated from libraries prepared from the TIL predict that STRL22 and STRL33 encode proteins of 374 and 342 amino acids respectively. The STRL22 gene is expressed in peripheral blood lymphocytes, TIL, B cells and lymphoid tissues and the STRL33 gene is expressed in TIL, in activated PBL, and in lymphoid tissues. By screening novel chemokines for agonist activity, the chemokine MIP-3alpha was found to be a ligand for STRL22, which has been re-named CC chemokine receptor 6 (CCR6). MIP-3alpha is unusual among CC chemokines in that it does not target moncytes, but specifically stimulates lymphocytes. Using an assay to detect fusion between cells expressing HIV-1 envelope glycoproteins (Envs) and cells expressing CD4 and candidate co-receptors done in collaboration with Edward Berger's laboratory, are determined that STRL33 could function as a co-receptor for Envs from diverse strains of HIV-1 as well as SIV. In collaboration with Keith Peden of the FDA, using STRL33-transfected cell lines, we showed that STRL33 could mediate infection by HIV-1ELI and by SIVMAC. Because STRL33 is active with a broader range of Envs than the other co-receptors described to date, STRL33 may be of particular value in discovering the structural determinates of Env/co-receptor interactions and may be of importance in the pathogenesis of HIV/SIV disease.
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