title: Oxygen dependence of nitric oxide-mediated signaling.
abstract: Nitric oxide (•NO) is a biologically important short-lived free radical signaling molecule. Both the enzymatic synthesis and the predominant forms of cellular metabolism of •NO are oxygen-dependent. For these reasons, changes in local oxygen concentrations can have a profound influence on steady-state •NO concentrations. Many proteins are regulated by •NO in a concentration-dependent manner, but their responses are elicited at different thresholds. Using soluble guanylyl cyclase (sGC) and p53 as model •NO-sensitive proteins, we demonstrate that their concentration-dependent responses to •NO are a function of the O2 concentration. p53 requires relatively high steady-state •NO concentrations (>600 nM) to induce its phosphorylation (P-ser-15), whereas sGC responds to low •NO concentrations (<100 nM). At a constant rate of •NO production (liberation from •NO-donors), decreasing the O2 concentration (1%) lowers the rate of •NO metabolism. This raises steady-state •NO concentrations and allows p53 activation at lower doses of the •NO donor. Enzymatic •NO production, however, requires O2 as a substrate such that decreasing the O2 concentration below the K m for O2 for nitric oxide synthase (NOS) will decrease the production of •NO. We demonstrate that the amount of •NO produced by RAW 264.7 macrophages is a function of the O2 concentration. Differences in rates of •NO production and •NO metabolism result in differential sGC activation that is not linear with respect to O2. There is an optimal O2 concentration (≈5-8%) where a balance between the synthesis and metabolism of •NO is established such that both the •NO concentration and sGC activation are maximal.
authors.affiliation: Departments of Medicinal Chemistry & Pharmacognosy, University of Illinois at Chicago, Chicago, IL 60612-7231, United States.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Hickok
authors.forename: Divya
authors.initials: D
authors.lastname: Vasudevan
authors.forename: Kate
authors.initials: K
authors.lastname: Jablonski
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Thomas
mesh_terms: D000818:Animals; D002460:Cell Line; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D061986:MCF-7 Cells; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010766:Phosphorylation; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction; D000071756:Soluble Guanylyl Cyclase; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D018160:Receptors, Cytoplasmic and Nuclear; D016159:Tumor Suppressor Protein p53; D009569:Nitric Oxide; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase; D010100:Oxygen
keywords: Autooxidation; BH4, tetrahydrobiopterin; DETA/NO, (Z)-1-[N-(2-aminoethyl)–N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate; FAD, flavin adenine dinucleotide; FMN, flavin mononucleotide; Km, Michaelis constant; LPS, lipopolysaccharide; NADPH, nicotinamide adenine dinucleotide phosphate, reduced; NO2−, nitrite; NO3−, nitrate; Nitric oxide; Nitric oxide synthase; O2, oxygen; ODQ, 1H-[1,2,4]Oxadiazolo[4,3–a]quinoxalin-1-one; Oxygen; P-Ser-15, phospho-serine 15; Sper/NO, (Z)-1-[N-[3–aminopropyl]–N-[4-(3-aminopropylammonio)butyl]-amino]diazen-1-ium-1,2-diolate; cGMP, cyclic guanosine monophosphate; eNOS, endothelial nitric oxide synthase; iNOS, inducible nitric oxide synthase; nNOS, neuronal nitric oxide synthase; p53; sGC; sGC, soluble guanylyl cyclase; •NO, nitric oxide
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