REGULATION OF HIV-1 CORECEPTORS

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The chemokines are a family of structurally related peptides that interact through cell surface G-protein coupled receptors in leukocytes to mediate diverse biological and biochemical activities such as adhesion, directed migration and activation. They play a major role in the pathophysiology of many inflammatory disorders. Chemokine receptors CCR5 or CXCR4 were identified as essential co-receptors for the entry of human immunodeficiency virus HIV-1 into CD4 positive cells. While CCR5 is the target for the entry of primary viruses CXCR4 may be important in the progression to AIDS from asymptomatic infection. The overall objective of the parent proposal is to delineate the pathways of CXCR4 signaling, desensitization and internalization using the RBL-2H3 cells stably co-expressing epitope-tagged native or mutated CXCR4 along with human CD4. In this AIDS-FIRCA, Dr. Sozzani proposes to utilize many reagents (epitope-tagged, green fluorescent protein tagged native and mutated CXCR4 DNAs and transfected RBL cell lines) developed for the parent proposal to determine the role of MAPKs on cPLA2 activation by the ligand SDF-1 and the relevance of this pathway to leukocyte chemotaxis using both pharmacological and biochemical approach. The ability of the HIV-1 envelope glycoproteins (gp120) to induce second messenger formation in CXCR4-expressing RBL-2H3 will be investigated. Activation of MAPKs, and cPLA2 will be evaluated and correlated with the ability of gp120 proteins to induce cell migration. The parent laboratory is utilizing and HIV-1 infection permissive human astroglioma cell line, U87, transfected with human CD4 and native or mutated CXCR4 to determine the role of the signaling evens and internalization in HiV-1 infection. The studies on cPLA2 and MAPKs in RBLs will provide a basis for extension of the same to human cell lines in the parent laboratory and to determine the role of these pathways in HIV-1 infection.