The overall goal of this project is to engage undergraduate and graduate students in innovative studies in molecular toxinology, studies that have the potential to contribute to important advances in our understanding of the pathophysiology of snakebite. Snakebite is a huge global health problem, causing serious injury to 2.7 million men, women and children and claiming an estimated 125,000 lives annually. In spite of its importance as a global health issue, very little is known of the pathophysiology of snakebite. The scientific premise for our study is that a specific family of snake venom toxins, the Cysteine-Rich Secretory Proteins (svCRiSPs), plays a critical role in snakebite by targeting blood and lymphatic vessels in the region of the bite and rapidly and dramatically increasing vascular permeability. We hypothesize that svCRiSPs increase blood and lymphatic endothelial cell permeability. The increase in interstitial fluid flow that results from decreased endothelial cell barrier function, accelerates the transit of the venom from its site of deposition in the bite into the systemic circulation. Once delivered into the systemic circulation, the numerous toxins in the venom gain access to their target tissues, causing the rapid immobilization and death of the snake's prey. To test our hypothesis we will address two distinct but complementary Specific Aims: Specific Aim 1: To profile the effect of svCRiSPs on vascular permeability and endothelial cell function. Teams of undergraduate students enrolled in research courses will purify and characterize svCRISP's from the venom some of the most medically significant species of venomous snakes housed in our collection. Characterization will include in vitro assays of blood and lymphatic endothelial cell barrier function and in vivo assays of vascular permeability. Specific Aim 2. To characterize the cellular and molecular basis for the effects of Hellerin, a newly identified crotalid svCRiSP, on the function of blood and lymphatic endothelial cells. Advanced undergraduate and graduate students will investigate the mechanism of action of Hellerin an svCRiSP isolated from the venom of the Southern Pacific Rattlesnake. Students will test the activity of Hellerin on the proliferation and barrier function of blood and lymphatic endothelial cells and will characterize the cell signaling pathways and membrane receptors that mediate the effects of the toxin on endothelial cell function. The proposed studies will support the educational goals of our program by providing undergraduate and graduate students with hands-on research experience that provides an introduction to the opportunities available for careers in biomedical research. This research program will also enhance the academic environment of our university by promoting an important program of global health research. Knowledge gained from these studies will provide insights into the molecular mechanisms that underlie the effects of svCRiSPs on vascular function and will contribute to our understanding of the pathophysiology of snakebite.