Fellowship Dejan Nikolic: The Role of integrin Signaling Pathways in SR-A-Mediated Cell Adhesion

Class Ascavenger receptors (SR-A)participate in multipl:e macrophage functions, includingendocytosis, phagocytosisand celladhesion. SR-A-mediatedmacrophageatlachmentand retentionatsite$ of inflammation involves SR.A-dependent bindingta modified 8!.xtracellularmatrix (ECM) proteins. Therefore, in addition to uptakeofmodi.fied lipoproteins such as oxidiz,ed LDt, SR-A.-mediated macrbphageadhesi!on and retention at atherosclerotic lesions likelycontributes to pathogenesis of a'theroscleroticdisease. We found that SR-A-dependentcell adhesion Invoil/es actin polymerization andfUopodia and focaf adhesion complex formation; morphological changes typically associated with integrin-dependent cell adhesion, Although signaling mechanisms involved in SR.A-ll1ediated eell adhesion are not known, iritegrin-mediated adhesion involves receptor clustering at the cellsurfaoe and activation of Rho GTPases (Cdc42, Rac, Rho) and focal adhesion kinase (F.AK).Using methods, simil.arto those IJsed to study integrin-mediated signaling, I will test the hypothesis that SR-A mediated cell adhesion involves receptor clustering on the cell surface and activation of Rho-like GTPases and FAK The specific aims of this proposal ar,s: 1) To delineate the role of Rho-like small GTPases (Cdc42,Rac, Rho) and FAK in SR-A-mediated adhesion, and 2) To elucidate whether SR-A aggregation (clustering) is sufficient t,c induce the.adhesion signals. Because SR-A-dependerit adhesion and retention of macro phages may playa critical role in atherosclerosis development :identification of these si,gnaling molecules, proposed in Aim 1, wUl significantly expand our knowledge in this field. The results of experiments proposed in Aim 2 will provide additional information whether SR-Adustering at the cell surface is suffici,ent to induce Intracellular signaling associated with adhesion-induced cell si,gnaling. The following techniques will be employed in these specific aims: cell culture, transfection, SDS-PAGE.,.Western blotting, pull-down assays, oell adhesion assay, immunocytochemistry and confocal microscopy,