Sternfeld M, Ming G, Song H, Sela K, Timberg R, Poo M, Soreq H
Department of Biological Chemistry, The Life Sciences Institute, The Hebrew University of Jerusalem, 91904, Israel.
J Neurosci. 1998 Feb 15;18(4):1240-9. doi: 10.1523/JNEUROSCI.18-04-01240.1998.
Accumulated indirect evidence suggests nerve growth-promoting activities for acetylcholinesterase (AChE). To determine unequivocally whether such activities exist, whether they are related to the capacities of this enzyme to hydrolyze acetylcholine and enhance synapse development, and whether they are associated with alternative splicing variants of AChEmRNA, we used four recombinant human AChEDNA vectors. When Xenopus laevis embryos were injected with a vector expressing the synapse-characteristic human AChE-E6, which contains the exon 6-encoded C terminus, cultured spinal neurons expressing this enzyme grew threefold faster than co-cultured control neurons. Similar enhancement occurred in neurons expressing an insertion-inactivated human AChE-E6-IN protein, containing the same C terminus, and displaying indistinguishable immunochemical and electrophoretic migration properties from AChE-E6, but incapable of hydrolyzing acetylcholine. In contrast, the nonsynaptic secretory human AChE-I4, which contains the pseudointron 4-derived C terminus, did not affect neurite growth. Moreover, no growth promotion occurred in neurons expressing the catalytically active C-terminally truncated human AChE-E4, demonstrating a dominant role for the E6-derived C terminus in neurite extension. Also, AChE-E6 was the only active enzyme variant to be associated with Xenopus membranes. However, postsynaptic length measurements demonstrated that both AChE-E6 and AChE-E4 enhanced the development of neuromuscular junctions in vivo, unlike the catalytically inert AChE-E6-IN and the nonsynaptic AChE-I4. These findings demonstrate an evolutionarily conserved synaptogenic activity for AChE that depends on its hydrolytic capacity but not on its membrane association. Moreover, this synaptogenic effect differs from the growth-promoting activity of AChE, which is unrelated to its hydrolytic capacity yet depends on its exon 6-mediated membrane association.
累积的间接证据表明乙酰胆碱酯酶（AChE）具有促进神经生长的活性。为了明确此类活性是否存在、它们是否与该酶水解乙酰胆碱及促进突触发育的能力相关，以及它们是否与AChE mRNA的可变剪接变体有关，我们使用了四种重组人AChE DNA载体。当向非洲爪蟾胚胎注射表达具有突触特征的人AChE-E6（其包含外显子6编码的C末端）的载体时，表达这种酶的培养脊髓神经元生长速度比共培养的对照神经元快三倍。在表达插入失活的人AChE-E6-IN蛋白（含有相同的C末端，且免疫化学和电泳迁移特性与AChE-E6无法区分，但无水解乙酰胆碱能力）的神经元中也出现了类似的增强。相比之下，含有假内含子4衍生C末端的非突触分泌型人AChE-I4对神经突生长没有影响。此外，在表达具有催化活性的C末端截短的人AChE-E4的神经元中未出现生长促进现象，这表明E6衍生的C末端在神经突延伸中起主导作用。而且，AChE-E6是唯一与非洲爪蟾膜相关的活性酶变体。然而，突触后长度测量表明，与催化惰性的AChE-E6-IN和非突触的AChE-I4不同，AChE-E6和AChE-E4在体内均增强了神经肌肉接头的发育。这些发现证明了AChE具有一种进化上保守的突触形成活性[1]，其依赖于水解能力而非膜结合。此外，这种突触形成效应不同于AChE的生长促进活性，后者与其水解能力无关，但依赖于其外显子6介导的膜结合。 [1] 此处“进化上保守的突触形成活性”在原文中为“evolutionarily conserved synaptogenic activity”，为使译文更符合中文表达习惯，添加了注释说明。在实际翻译中，可根据具体要求灵活处理。
