M1 muscarinic receptors stimulate rapid and prolonged phases of neuronal nitric oxide synthase activity: Involvement of different calcium pools

Diane R. Wotta, Ann M. Parsons, Jingru Hu, Andrew W. Grande, Esam E. El-Fakahany

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19 Scopus citations

Abstract

This study shows that activation of M1 muscarinic receptors, when coexpressed in Chinese hamster ovary (CHO)-K1 cells with neuronal nitric oxide (NO) synthase (nNOS), produces early and late phases of elevation of both intracellular Ca2+ concentration and nNOS activity. We examined the relationship between receptor-mediated increases in intracellular Ca2+ concentration and activation of nNOS over both short and long intervals using guanosine 3',5'-cyclic monophosphate (cGMP) formation as a measure of nNOS activity. The rapid phase of nNOS activation was dependent on release of Ca2+ from intracellular stores in both the CHO M1/nNOS transfected cells and in neuroblastoma (N1E-115) cells, in which muscarinic receptors and nNOS are endogenously expressed. Two single point mutations in the M1 muscarinic receptor that have previously been shown to uncouple differentially the receptor from phosphoinositide hydrolysis produced parallel attenuation of the rapid phase of nNOS activation. Characterization of the prolonged phase of nNOS activation was done using the conversion of L-[3H]arginine to L- [3H]citrulline as well as cGMP formation following stimulation of M1 muscarinic receptors for 60 min. Both responses were dependent on influx of extracellular Ca2+ and were accompanied by prolonged formation of NO at functionally effective levels as late as 60 min following receptor activation. Therefore, this study demonstrates for the first time the existence of two mechanistically distinct phases of nNOS activation that are dependent on different sources of Ca2+.

Original languageEnglish (US)
Pages (from-to)487-497
Number of pages11
JournalJournal of Neurochemistry
Volume71
Issue number2
StatePublished - Aug 1 1998

Keywords

  • Acetylcholine
  • Calcium
  • Muscarinic system
  • Receptor
  • Signaling

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