Regulation of leukocyte recruitment and endothelial functions by LSP1-mediated protein-protein interactions

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Inflammation is the body's response to infection or injury. During inflammation, there are complex interactions between the white blood cells (leukocytes) and endothelial cells, the cells lining the blood vessel wall. Leukocyte-specific protein 1 (LSP1) is a signaling molecule in leukocytes and endothelial cells. It has an important role in leukocyte-endothelial interactions. When there is an inflammation, LSP1 becomes activated, regulates the permeability of the blood vessel wall, moves in different compartments and can interact with many other proteins in cells. Our research have found clear, biological evidence that, (1) endothelial cell LSP1 can attach to another small and short protein called SUMO1, i.e., LSP1 is post-translationally modified by SUMO1; (2) when there is an inflammation, endothelial LSP1 interacts with intracellular scaffold proteins ezrin-radixin-moesin (ERM) and F-actins; and (3) at arterial blood vessels, endothelial LSP1 interacts with an endothelial protein called eNOS and regulates endothelial functions that are related to blood pressure regulation. We hypothesize that endothelial LSP1 interacts with SUMO1, ERM and eNOS proteins in endothelial cells and by doing so regulates multiple endothelial functions, including leukocyte-endothelial interactions, blood vessel permeability changes and blood pressure regulation. ******Firstly, we will use cultured endothelial cells and many biological techniques to establish that LSP1 is indeed attached (i.e., post-translationally modified) by SUMO1 for maintaining LSP1's stability and functions in endothelial cells. Secondly, we will provide strong scientific evidence that endothelial LSP1 interacts with ERM proteins when endothelial cells are activated and thereby regulates trans-endothelial migration of leukocytes and blood vessel permeability increases in inflammation. We will also watch under microscope the images of LSP1 interacting with SUMO1 and ERM. Thirdly, we will verify that LSP1-deficiency causes hypertension in the mice lacking LSP1. We have the expertise and equipment to measure and compare the contraction and relaxation responses of arterial vessels isolated from the mice lacking LSP1 and control mice having LSP1. Also using cultured endothelial cells, we will determine physical and functional interactions between LSP1 and eNOS. This study will add our scientific knowledge on the mechanisms of LSP1 interacting with SUMO1, ERM and eNOS and reveal important functions of these interactions.