Project Summary This application has as its theme the integrins, their regulation and their contribution to the functional responses of blood and vascular cells. The integrins of focus are αMβ2 (Mac-1), αIIbβ3, αVβ3, and α5β1 but findings should apply to broadly integrins. The cells of emphasis are vascular cells- endothelial cells, smooth muscle cells and pericytes- and blood cells- leukocytes and platelets. On the blood cells, the conjugation of Mac-1 on leukocytes and GPIb on platelets will be considered. Major emphasis will be placed on the molecules that regulate integrin function- kindlins, talin and paxillin- to determine how they collaborate to regulate integrin activation. The function of these cytoskeletal proteins independent of integrin activating activity will also be dissected. The Program consists of three projects, each directed by an accomplished faculty member at their home institutions, Cleveland Clinic, University Hospitals of Cleveland and Case Western Reserve University which are all closely located and governed by interinstitutional agreements. Dr. Edward F. Plow, Ph.D. will serve as Program Director and lead Project 1. This project deals with the mechanisms by which kindlin-2 regulates both integrin-dependent and independent responses of blood vessel cells. Molecular, cellular and unique mouse models are all brought to bear to determine how kindlin-2 serves as a master regulator of vascular cell responses. In Project 2, Dr. Jun Qin will use high resolution structural approaches in combination with mutagenesis and cellular studies to determine how talin regulate integrin activation and cooperates with kindlins and paxillin to gain such novel insights. He will determine how talin interacts with actin to control organization of the cytoskeleton. Dr. Daniel Simon, M.D. will lead Project 3 and will consider how engagement of integrin Mac-1 on leukocytes and GPIb on platelets regulates the participation of these cells in inflammation and thrombosis. His studies range from basic structural approaches to translational studies in mice and to humans to provide insights into their thrombotic and inflammatory contributions to systemic lupus erythematosus. The Program is supported by two Scientific Cores, Protein Expression and Purification (Core B), and Animal Models and Tissue Analysis (Core C) as well as by an Administrative Core (AC1). A common objective of the Program is to continue and create new collaborations among the Projects and their Leaders to resolve the structural and biological mechanisms that regulate the functions of integrins in blood and vascular cells. The information derived from these studies will provide insights into biologically important responses regulated by integrins and their activation that are relevant to thrombosis and cardiovascular diseases.