Intracellular cyclic AMP regulates the expression of acetylcholinesterase (AChE) during myogenesis in C2C12 cells

Acetycholinesterase (AChE) localizes at vertebrate neuromuscular junctions to hydrolyse acetylcholine. Previous results indicated that muscle AChE expression could be regulated by motor neuron via nerve-derived factors, such as calcitonin gene-related peptide (CGRP) and muscular activity. However, the intrinsic factor(s) by muscle itself may also play an important role in the regulation of AChE. In order to analyze the molecular mechanism of AChE regulation during myogenesis, a 2.2 kb human AChE promoter tagged with a luciferase reporter gene (Hp-Luc) was stably transfected into C2C12 cells. The profile of promoter-driven luciferase activity during myogenesis was similar to that of endogenous mouse AChE activity; both of them were increased during myogenesis. The level of intracellular cAMP, the phoshorylation pattern of cAMP-responsive element binding protein (CREB) and the activity of cAMP-responsive element (CRE) were down regulated during the myotube formation. The mutation of the CRE site on human AChE promoter altered the original myogenic profile of the promoter activity. Therefore, our results suggest that the intracellular cAMP in muscle during myogenesis serves as a suppressive element on the expression of AChE