Submitted on October 10, 2002
Accepted on December 10, 2002
Colocalization, but differential regulation of neuronal NO synthase and the nicotinic acetylcholine receptor in C2C12 myotubes
Jutta G Ebert1, Marek Zelenka1, Ingolf Gath1, Ute Godtel-Armbrust1, and Ulrich Forstermann1*
1 Pharmacology, Gutenberg University, Mainz, Germany
* To whom correspondence should be addressed. E-mail: ulrich.forstermann{at}uni-mainz.de.
In mammalian skeletal muscle, neuronal-type NO synthase (nNOS) is found 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, co-immunoprecipitation 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 lipopolysaccharide downregulated the expression of nNOS in skeletal muscle, and treatment of C2C12 cells with bacterial lipopolysaccharide 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.
