Tsim K W, Choi R C, Dong T T, Wan D C
Department of Biology, Hong Kong University of Science and Technology, Kowloon, Hong Kong.
J Neurochem. 1997 Feb;68(2):479-87. doi: 10.1046/j.1471-4159.1997.68020479.x.
In vertebrate neuromuscular junctions, the postsynaptic specializations include the accumulation of acetylcholinesterase (AChE) at the synaptic basal lamina and the muscle fiber. Several lines of evidence indicate that the presynaptic motor neuron is able to synthesize and secrete AChE at the neuromuscular junctions. By using anti-AChE catalytic subunit, anti-butyrylcholinesterase (BuChE) catalytic subunit, and anti-AChE collagenous tail monoclonal antibodies, we demonstrated that the motor neurons of chick spinal cord expressed AChE in vivo and the predominant AChE was the globular form of the enzyme. Neither asymmetric AChE nor BuChE was detected in the motor neurons. The molecular mass of AChE catalytic subunit in the motor neuron was approximately 105 kDa, which was similar to that of the globular enzyme from low-salt extracts of muscle; both of them were approximately 5 kDa smaller than the asymmetric AChE from high-salt extracts of muscle. The level of AChE expression in the motor neurons decreased, as found by immunochemical and enzymatic analysis, during the different stages of the chick's development and after nerve lesion. Thus, the AChE activity at the neuromuscular junctions that is contributed by the presynaptic motor neurons is primarily the globular, not the asymmetric, form of the enzyme, and these contributions decreased toward maturity and after denervation.
在脊椎动物的神经肌肉接头处，突触后特化包括乙酰胆碱酯酶（AChE）在突触基底膜和肌纤维处的积聚。多条证据表明，突触前运动神经元能够在神经肌肉接头处合成并分泌AChE。通过使用抗AChE催化亚基、抗丁酰胆碱酯酶（BuChE）催化亚基和抗AChE胶原尾单克隆抗体，我们证明了鸡脊髓运动神经元在体内表达AChE，且主要的AChE是该酶的球状形式。在运动神经元中未检测到不对称AChE和BuChE。运动神经元中AChE催化亚基的分子量约为105 kDa，这与来自肌肉低盐提取物的球状酶相似；它们两者都比来自肌肉高盐提取物的不对称AChE小约5 kDa。通过免疫化学和酶学分析发现，在鸡发育的不同阶段以及神经损伤后，运动神经元中AChE的表达水平下降。因此，由突触前运动神经元贡献的神经肌肉接头处的AChE活性主要是酶的球状形式，而非不对称形式，并且这些贡献在发育成熟和去神经支配后会降低。
