Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Am J Physiol Gastrointest Liver Physiol. 2008 Mar;294(3):G627-34. Epub 2007 Dec 20.

Active and inactive pools of nNOS in the nerve terminals in mouse gut: implications for nitrergic neurotransmission.

Author information

  • 1Center for Swallowing and Motility Disorders, Veterans Affairs Boston Healthcare System and Harvard Medical School, Boston, Massachusetts, USA.

Abstract

Nitric oxide (NO) is responsible for nitrergic neurotransmission in the gut, and its release is dependent on its de novo synthesis by neuronal nitric oxide synthase (nNOS). The magnitude of NO synthesis and release during neurotransmission may be related to the fraction of catalytically active nNOS out of a larger pool of inactive nNOS in the nerve terminals. The purpose of the present study was to identify catalytically active and inactive pools of nNOS in the varicosities from mouse gut. Enteric varicosities were confirmed as nitrergic by colocalization of nNOS with the nerve varicosity marker synaptophysin. Low-temperature SDS-PAGE of these varicosity extracts showed 320-, 250-, and 155-kDa bands when blotted with anti-nNOS(1422-1433) and 320- and 155-kDa bands when blotted with anti-nNOS(1-20) antibodies, respectively. The 320- and 155-kDa bands represent dimers and monomers of nNOSalpha; the 250- and 135-kDa bands represent dimers and monomers of nNOSbeta. Immunoprecipitation with calmodulin (CaM) showed that a portion of nNOSalpha dimer was bound with CaM. On the other hand, a portion of nNOSalpha dimer, nNOSbeta dimer, and all monomers lacked CaM binding. The CaM-lacking nNOS fractions reacted with anti-serine 847-phospho-nNOS. In vitro assays of NO production revealed that only the CaM-bound dimeric nNOSalpha was catalytically active; all other forms were inactive. We suggest that the amount of catalytically active nNOSalpha dimers may be regulated by serine 847 phosphorylation and equilibrium between dimers and monomers of nNOSalpha.

PMID:
18096606
[PubMed - indexed for MEDLINE]
PMCID:
PMC2497337
Free PMC Article

Images from this publication.See all images (6)Free text

Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk