title: Nitric oxide inhibition of ERK1/2 activity in cells expressing neuronal nitric-oxide synthase.
abstract: Neuronal nitric-oxide synthase (nNOS) is a constitutively expressed enzyme responsible for the production of nitric oxide (NO*) from l-arginine and O2. Nitric oxide is an intra- and intercellular messenger that mediates a diversity of signaling pathways in target cells. In the absence of l-arginine, nNOS has been shown to generate superoxide (O2*). Superoxide, either directly or through its self-dismutation to H2O2, is likewise believed to be a cell-signaling agent. Because nNOS can generate NO* and O2*, we examined the activation of cellular signal transduction pathways in nNOS-transfected cells grown in the presence or absence of l-arginine. Spin trapping/EPR spectroscopy confirmed that stimulated nNOS-transfected cells grown in an l-arginine environment secreted NO* into the surrounding milieu. Production of NO* blocked Ca2+ ionophore-induced activation of the ERK1/2 through a mechanism involving inhibition of the Ras G-protein and Raf-1 kinase. In contrast, ERK activation was largely unaffected in nNOS-transfected cells grown in l-arginine-free media. Inhibition of nNOS-generated NO* with the competitive NOS inhibitor, NG-nitro-l-arginine methyl ester, in cells grown in l-arginine restored ERK1/2 activation to levels similar to that found when nNOS was activated in l-arginine-free media. These findings indicate that nNOS can differentially regulate the ERK signal transduction pathway in a manner dependent on the presence of l-arginine and the production of NO*.
authors: Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA.
authors: Kimberly W
authors: KW
authors: Raines
authors: Guan-Liang
authors: GL
authors: Cao
authors: Supatra
authors: S
authors: Porsuphatana
authors: Pei
authors: P
authors: Tsai
authors: Gerald M
authors: GM
authors: Rosen
authors: Paul
authors: P
authors: Shapiro
mesh_terms: D001120:Arginine / Q000494:pharmacology; D002460:Cell Line; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D008954:Models, Biological; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014162:Transfection
chemical_list: D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D013481:Superoxides; D009569:Nitric Oxide; D001120:Arginine; C496320:NOS1 protein, human; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases