REGULATION OF EXTRACELLULAR SUPEROXIDE DISMUTASE BY PROT

National Jewish Health, Denver CO

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Abstract

National Jewish Medical Center in Denver Colorado is a well established center of excellence in pulmonary medicine. The laboratory of Dr. James Crapo has a long history of productive research in fife radical biology and is well equiped for fiiture research. I will use this highly productive environment to build my career in independent research and, by simultaneously completing a Ph.D. in cell and structural biology, I will have taken an unusual, but rigorous path to complete this goal. The Ph.D., which I started during my fellowship in Pulmonary and Critical Care Medicine, will be an integral part in my development into an independent scientist and in my fiirther studies of free radical biology in the lung. Superoxide plays an important role in inflammation and may also play a role in modulation of blood pressure. Superoxide dismutases are a highly conserved, ubiquitous family of enzymes which convert superoxide into hydrogen peroxide. Extracellular superoxide dismutase (EC-SOD) is the primary extracellular antioxidant enzyme; it is uniquely abundant in lung tissue and in vessel walls. A region within the carboxyterminus of this protein is rich in positive charge and is responsible for the distribution of the enzyme within extracellular spaces. Recently we have shown that this region can be specifically cleaved by an endoprotease. Three observations have made us think that proteolytic cleavage of this enzyme is physiologically significant: (1) the distribution of cleaved versus uncleaved EC-SOD varies among tissues; uncleaved or native EC-SOD predominates in vascular organs such as heart and aorta while cleaved EC-SOD is more prevalent in lung and liver; (2) we have recently found that total EC-SOD and the ratio of cleaved to native EC-SOD are increased during inflammation; and, (3) proteolytic cleavage occurs intracellularly. We propose to test the hypothesis that cells specifically regulate whether they secrete cleaved or intact EC-SOD based on the intended function EC-SOD. We further propose that a primary function of uncleaved EC-SOD is to modulate the EDRF response in blood vessels and that a primary function of cleaved EC-SOD is to protect the extracellular milieu from free radical mediated injury during inflammation. We expect to find that uncleaved EC-SOD predominates in blood vessels in both wild type and transgenic animals and that this EC-SOD activity will protect EDRF mediated vasodilation in aortic ring bath preparations. We further expect to show in cell culture and animal models that inflammation upregulates both total EC-SOD and the ratio of cleaved to intact EC-SOD. W will show that this correlates with a more diffuse distribution of the enzyme and a reduction of free radial mediated lung injury. This will not only define new aspects of the pathogenesis and regulation of vascular tone and inflammation, but can open new approaches to pharmacologically control these events.