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Afr Health Sci. 2011 Dec;11(4):526-34.

Inhibitors caveolin-1 and protein kinase G show differential subcellular colocalization with Nitric oxide synthase.

Author information

1
Department of Pharmacology, Lagos State University College of Medicine. 1 Oba Akinjobi Way, GRA, Ikeja, Lagos, P.M.B. 21266, Ikeja, Lagos, Nigeria. theresaadebola@yahoo.com

Abstract

BACKGROUND:

Nitric oxide synthase (NOS) is negatively regulated by protein-protein interactions with caveolin-1 before extracellular activating signals release it for nitric oxide (NO) production. Smooth muscle protein kinase G (PKG) is a down-stream effector of NO signaling for relaxation of vascular smooth muscle cells (SMC). The PKG is also found in endothelial cells and it inhibits activated NOS within endothelial cells.

METHODS:

We used confocal fluorescence microscopy to colocalize the inhibitors caveolin-1 and PKG with NOS in freshly isolated neonatal lamb endothelial cells in order to corroborate the speculation of their differential effects on NOS. The roles of caveolin-1 and PKG as regulators of NOS were investigated by examining their respective subcellular sites of colocalization with NOS using qualitative fluorescence immunohistochemistry and confocal microscopy.

RESULTS:

Caveolin-1 was colocalized with NOS in the plasma membrane and Golgi. The PKG1-beta isoform was colocalized with serine116 phosphorylated NOS in the cytosol and in vesicular structures seen in the endoplasmic reticulum and in the nuclear region.

CONCLUSION:

We conclude that unlike caveolin-1, a known pre-activation inhibitor of nascent NOS, PKG may be a post-activation inhibitor of NOS, possibly important for the recycling of the spent enzyme.

KEYWORDS:

caveolin-1; nitric oxide synthase; protein kinase G

PMID:
22649431
PMCID:
PMC3362974
[Indexed for MEDLINE]
Free PMC Article
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