Regulation and mechanism of nitric oxide synthase isozymes

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Nitric oxide (NO) is one of the most widespread signaling molecules in mammals and important in controlling nearly every cellular and organ function in the body.    Since NO plays multiple physiological roles in regulating varied and diverse organ functions, defects in NO production are also involved in a number of pathophysiological states including atherosclerosis, hypertension, stroke and vascular complications in diabetes.  NO is synthesized in the body by enzymes named nitric oxide synthases or NOS.  NOS enzymes are some of the most complex enzymes ever discovered.  Precise control of NOS enzymes is of potential therapeutic value since NO has diverse biological functions and is also a key part of several serious disease states. A significant number of fundamental questions about NOS need to be answered before we can take full advantage of the therapeutic potential of this target enzyme.  The long-term goals of our research program are to understand the regulation and mechanism of NOS enzymes and the role of NO in cell function, signalling and differentiation.  We use the recombinant forms of the three different mammalian NOS enzymes in our investigations.  Site-directed mutagenesis is used to decipher the role of important regions of the enzymes.  We learn about their fundamental properties by performing experiments on native and mutated forms of the enzymes.  For example, although all three enzymes are activated when bound to a calcium sensing protein called calmodulin, there are significant differences in the processes leading to the activation of each enzyme.  Our research program will provide an understanding of the important mechanism of calmodulin binding and activation of NOS enzymes.  We will also perform in vivo investigations using mammalian cell culture studies to understand how cell function, homeostasis and differentiation  as well as enzyme activity and are affected by the post-translational processing of the inducible NOS enzyme.  Gaining a better understanding of how these enzymes function may help in the development of therapies for a wide variety of diseases.