Vol. 284, Issue 4, C1065-C1072, April 2003
Colocalization but differential regulation of neuronal NO
synthase and nicotinic acetylcholine receptor in
C2C12 myotubes
Jutta G.
Ebert,
Marek
Zelenka,
Ingolf
Gath,
Ute
Gödtel-Armbrust, and
Ulrich
Förstermann
Department of Pharmacology, Johannes Gutenberg University,
D-55101 Mainz, Germany
In mammalian skeletal muscle,
neuronal-type nitric oxide synthase (nNOS) is found to be enriched at
neuromuscular endplates. Here we demonstrate the colocalization of the
nicotinic acetylcholine receptor (nAChR, stained with 
-bungarotoxin)
and nNOS (stained with a specific antibody) in murine
C2C12 myotubes. However, coimmunoprecipitation experiments demonstrated no evidence for a direct protein-protein association between the nAChR and nNOS in C2C12
myotubes. An antibody to the 1-subunit of the nAChR did
not coprecipitate nNOS, and an nNOS-specific antibody did not
precipitate the 1-subunit of the nAChR. Treatment of
mice with bacterial LPS downregulated the expression of nNOS in
skeletal muscle, and treatment of C2C12 cells
with bacterial LPS and interferon-
markedly decreased nNOS mRNA and
protein expression. In contrast, mRNA and protein of the nAChR (-,
-, and 
-subunits) remained unchanged at the mRNA and protein
levels. These data demonstrate that nNOS and the nAChR are colocalized
in murine skeletal muscle and C2C12 cells but differ in their expressional regulation.
nitric oxide synthase I; nicotinic acetylcholine receptor; colocalization; expressional regulation; ribonuclease protection
analysis
