Molecular Regulation of Human iNOS by Phosphorylation

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DESCRIPTION (provided by applicant): Overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been implicated in the pathogenesis of several diseases including airway lung inflammation. The overall objective of this proposal is to understand the posttranslational mechanisms of cellular turnover of iNOS and thus lay the groundwork for future studies aiming at controlling NO synthesis. Our preliminary data suggest that iNOS is subject to regulation by phosphorylation precedes its ubiquitination. We propose to test the following hypotheses: A) The specific ubiquitin ligase that links ubiquitin to iNOS binds preferentially to phosphorylated iNOS. Thus phosphorylation of specific iNOS residue(s) is critical for iNOS ubiquitination and degraqdation. B) Cells maintain a tight control over NO synthesis by maintaining a robust rate of iNOS turnover that is modulated by cellular factors. To test these hypotheses we propose studies with the following Specific Aims; Aim 1: Elucidation of the role of phosphorylation in iNOS turnover and determining specific phosporylated residues; Aim 2: Characterization of the rate of iNOS turnover and cellular factors that modulate it. The rational for the proposed studies is that once these mechanisms are understood, therapeutic strategies can be designed to alter these pathways and modulate iNOS turnover.