Leukocyte recruitment from the blood stream and into surrounding tissues is a critical event in the inflammatory process. This process is initiated by endothelial activation, followed by leukocyte rolling, firm adhesion, and finally transendothelial migration (TEM). Firm adhesion of leukocytes is primarily mediated by leukocyte integrins binding to endothelial integrin ligands, ICAM-1 and VCAM-1, both of which have been shown to localize in ring like structures at sites of leukocyte adhesion. ICAM-1 is composed of an extracellular region containing 5 Ig domains, a transmembrane region, and a 28 amino acid cytoplasmic tail. This short cytoplasmic tail associates with activated Src family kinases (SFK), cortactin, and a number of other cytoskeletal adapter proteins. Although it is clear that SFK play a vital role in leukocyte transmigration, very little is known about how, when, or where SFK are activated during this process. Specific Aim 1 will address spatial and temporal dynamics of SFK activation and Specific Aim 2 will address the role of the ICAM-1 cytoplasmic tail in mediating TEM tunnel complex formation and SFK activation. This project will provide a better understanding of mechanisms involved in leukocyte transmigration with the long term goal of identifying molecular targets for inhibiting detrimental inflammation such as that found in atherosclerosis. If approved, this project will be funded through an F32 grant as part of the Ruth L. Kirschstein National Research Service Award. PUBLIC HEALTH RELEVANCE: This project will examine molecular mechanisms in involved in the migration of leukocytes out of the blood stream and into surrounding tissues. Knowledge gained in this project will be valuable for the development of new drugs to inhibit leukocyte migration and thus reduce inflammation.