IDENTIFICATION OF INTERACTIONS BETWEEN NITRIC OXIDE SYNTHASE AND CALMODULIN

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Nitric oxide synthase (NOS) plays a role in a variety of physiological functions from smooth muscle relaxation to cell-cell signaling in neurons. This enzyme catalyzes the oxidation of arginine to generate the multifunctional small molecule nitric oxide (¿NO). The unregulated production of ¿NO can lead to a number of pathological conditions such as stroke and Alzheimer¿s disease. There are three distinct isoforms of NOS that are differentially regulated by calmodulin (CaM). The isoforms found in neuronal and endothelial cells are regulated by the reversible binding of Ca2+/CaM, while the form found in macrophages (inducible) binds CaM tight enough to be seemingly irreversible.1 Previous research has demonstrated that the neuronal and the inducible NOS have very different requirements for which Ca2+ binding site of CaM must be Ca2+ bound in order to achieve activation, and suggests that the interactions between CaM and these two NOS isoforms is in opposite orientation.2,3 In lieu of molecular structures of these proteins, understanding this phenomenon requires studies geared at the gradual unraveling of the interactions and then piecing the information back together. The long-term objective of Dr. Stevens-Truss¿ laboratory is to understand the mechanisms underlying CaM¿s binding to and regulation of NOS. Mass spectrometry offers a tool that can be used to unravel these interactions. Traditional protein fingerprinting methodologies coupled with mass spectrometry are planned for use in this project, in an attempt to develop ways to study the interactions between CaM and the various NOS isoforms. This research is important because (i) it will increase our understanding of the overall folded structure of NOS as it relates to CaM binding and activation, (ii) it will shed light on the still enigmatic role of CaM in binding and activating over 30 different proteins, and (iii) it will advance efforts to design NOS isoform selective inhibitors. Moreover, these studies will aid in our understanding of factors that disrupt protein-protein interactions such as light energy collisions. Nitric oxide synthase (NOS) plays a role in a variety of physiological functions from smooth muscle relaxation to cell-cell signaling in neurons. This enzyme catalyzes the oxidation of arginine to generate the multifunctional small molecule nitric oxide (¿NO). The unregulated production of ¿NO can lead to a number of pathological conditions such as stroke and Alzheimer¿s disease. There are three distinct isoforms of NOS that are differentially regulated by calmodulin (CaM). The isoforms found in neuronal and endothelial cells are regulated by the reversible binding of Ca2+/CaM, while the form found in macrophages (inducible) binds CaM tight enough to be seemingly irreversible.1 Previous research has demonstrated that the neuronal and the inducible NOS have very different requirements for which Ca2+ binding site of CaM must be Ca2+ bound in order to achieve activation, and suggests that the interactions between CaM and these two NOS isoforms is in opposite orientation.2,3 In lieu of molecular structures of these proteins, understanding this phenomenon requires studies geared at the gradual unraveling of the interactions and then piecing the information back together. The long-term objective of Dr. Stevens-Truss¿ laboratory is to understand the mechanisms underlying CaM¿s binding to and regulation of NOS. Mass spectrometry offers a tool that can be used to unravel these interactions. Traditional protein fingerprinting methodologies coupled with mass spectrometry are planned for use in this project, in an attempt to develop ways to study the interactions between CaM and the various NOS isoforms. This research is important because (i) it will increase our understanding of the overall folded structure of NOS as it relates to CaM binding and activation, (ii) it will shed light on the still enigmatic role of CaM in binding and activating over 30 different proteins, and (iii) it will advance efforts to design NOS isoform selective inhibitors. Moreover, these studies will aid in our understanding of factors that disrupt protein-protein interactions such as light energy collisions.