Investigative ophthalmology & visual science · 2001
Nitric oxide attenuates alpha(2)-adrenergic receptors by ADP-ribosylation of G(i)alpha in ciliary epithelium.
СтатьяПоддержка исследования: вне правительства СШАПоддержка службы здравоохранения СШАНазвание и аннотация: Перевод пока не подготовлен
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Moroi S E, Hao Y, Sitaramayya A
Аннотация
PURPOSE: To determine the mechanism by which nitric oxide (NO) regulates alpha(2)-adrenergic receptor coupling to adenylyl cyclase in bovine ciliary epithelium.
METHODS: Ciliary epithelial explants were dissected, cultured, and labeled with [(3)H]adenine. [(3)H]Adenosine 3',5'-cyclic monophosphate (cAMP) was measured under basal conditions and after exposure to forskolin, isoproterenol, clonidine, yohimbine, pertussis toxin, and the NO donor spermine-NO. Endogenous and NO-stimulated ADP-ribosylation of ciliary epithelial membrane proteins was determined by [(32)P]nicotinamide adenosine diphosphate (NAD) labeling and autoradiography. The three isoforms of the G(i)alpha protein subunit were evaluated by Western blot analysis.
RESULTS: Basal [(3)H]cAMP content was 13.4 +/- 1.3 picomoles/mg protein (SEM). Both isoproterenol and forskolin stimulated [(3)H]cAMP accumulation to 36.0 +/- 3.9 and 73.2 +/- 17.5 picomoles/mg protein, respectively. Clonidine did not affect basal [(3)H]cAMP levels, but attenuated both isoproterenol- and forskolin-mediated [(3)H]cAMP accumulation to 23.2 +/- 4.4 and 31.6 +/- 4.6 picomoles/mg protein, respectively. Yohimbine antagonized the clonidine-mediated adenylyl cyclase inhibition. Pertussis toxin blocked the effect of clonidine. In the presence of the NO donor spermine-NO, the clonidine-mediated inhibition of forskolin- and isoproterenol-stimulated cAMP accumulation was attenuated completely. NO significantly stimulated endogenous [(32)P]ADP-ribosylation of a 40-kDa membrane protein. Western blot analysis with specific antibodies revealed expression of all three G(i) subtypes--G(i1)alpha, G(i2)alpha, and G(i3)alpha--in bovine ciliary epithelium.
CONCLUSIONS: NO attenuates alpha(2)-adrenergic receptor-mediated inhibition of adenylyl cyclase in ciliary epithelium through ADP-ribosylation of the G(i)alpha subunit. The findings demonstrate heterologous regulation between the NO and cAMP signaling pathways in ciliary epithelium.
METHODS: Ciliary epithelial explants were dissected, cultured, and labeled with [(3)H]adenine. [(3)H]Adenosine 3',5'-cyclic monophosphate (cAMP) was measured under basal conditions and after exposure to forskolin, isoproterenol, clonidine, yohimbine, pertussis toxin, and the NO donor spermine-NO. Endogenous and NO-stimulated ADP-ribosylation of ciliary epithelial membrane proteins was determined by [(32)P]nicotinamide adenosine diphosphate (NAD) labeling and autoradiography. The three isoforms of the G(i)alpha protein subunit were evaluated by Western blot analysis.
RESULTS: Basal [(3)H]cAMP content was 13.4 +/- 1.3 picomoles/mg protein (SEM). Both isoproterenol and forskolin stimulated [(3)H]cAMP accumulation to 36.0 +/- 3.9 and 73.2 +/- 17.5 picomoles/mg protein, respectively. Clonidine did not affect basal [(3)H]cAMP levels, but attenuated both isoproterenol- and forskolin-mediated [(3)H]cAMP accumulation to 23.2 +/- 4.4 and 31.6 +/- 4.6 picomoles/mg protein, respectively. Yohimbine antagonized the clonidine-mediated adenylyl cyclase inhibition. Pertussis toxin blocked the effect of clonidine. In the presence of the NO donor spermine-NO, the clonidine-mediated inhibition of forskolin- and isoproterenol-stimulated cAMP accumulation was attenuated completely. NO significantly stimulated endogenous [(32)P]ADP-ribosylation of a 40-kDa membrane protein. Western blot analysis with specific antibodies revealed expression of all three G(i) subtypes--G(i1)alpha, G(i2)alpha, and G(i3)alpha--in bovine ciliary epithelium.
CONCLUSIONS: NO attenuates alpha(2)-adrenergic receptor-mediated inhibition of adenylyl cyclase in ciliary epithelium through ADP-ribosylation of the G(i)alpha subunit. The findings demonstrate heterologous regulation between the NO and cAMP signaling pathways in ciliary epithelium.
Предметные рубрики MeSH
Adenosine Diphosphate RiboseAdenylyl Cyclase InhibitorsAdenylyl CyclasesAnimalsAutoradiographyBlotting, WesternCattleCells, CulturedCiliary BodyCyclic AMPEpithelial CellsEpitheliumGTP-Binding Protein alpha Subunits, Gi-GoNitric OxideNitric Oxide DonorsOrgan Culture TechniquesReceptors, Adrenergic, alpha-2Signal Transduction