Genetic analysis of collagen Q: roles in acetylcholinesterase and butyrylcholinesterase assembly and in synaptic structure and function.
Genetic analysis of collagen Q: roles in acetylcholinesterase and butyrylcholinesterase assembly and in synaptic structure and function.
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DOI：
10.1083/jcb.144.6.1349
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发表时间：
1999-03-22
影响因子：
7.8
通讯作者：
Sanes, J R
中科院分区：
文献类型：
--
作者：
Feng, G;Krejci, E;Molgo, J;Cunningham, J M;Massoulie, J;Sanes, J R
乙酰胆碱酯酶（AChE）以两种不对称形式存在，与称为Q（ColQ）的胶原亚基共价结合，以及可溶性或膜结合的球状形式。在骨骼肌神经肌肉接头处，不对称乙酰胆碱酯酶锚定在突触间隙的基底层，在那里它水解乙酰胆碱以终止突触传递。AChE也被假设在神经系统中发挥发育作用，ColQ也在一些AChE缺乏的组织中表达。为了寻找ColQ和AChE在突触和其他地方的作用，我们产生了ColQ缺陷突变小鼠。ColQ −/−小鼠在骨骼肌、心肌和大脑中完全缺乏不对称的AChE;它们也缺乏不对称形式的AChE同系物丁酰胆碱酯酶。因此，ColQ基因的产物是组装所有可检测的不对称乙酰胆碱酯酶和丁酰胆碱酯酶所必需的。令人惊讶的是，球状AChE四聚体也不存在于新生儿ColQ −/−肌肉中，这表明ColQ基因在AChE形式的组装或稳定中发挥作用，这些AChE形式本身不包含胶原亚基。组织化学、免疫组织化学、毒理学和电生理学测定均表明ColQ-/-神经肌肉接头处不存在AChE。尽管如此，神经肌肉功能最初是强大的，表明乙酰胆碱酯酶和ColQ不发挥强制性的作用，在早期阶段的突触。此外，由于突触乙酰胆碱酯酶的急性抑制对正常动物是致命的，突变体中必须有补偿机制，使突触在乙酰胆碱酯酶长期缺乏的情况下发挥作用。一种结构机制似乎是雪旺氏细胞对神经末梢的部分鞘化。然而，补偿是不完全的，因为缺乏ColQ和突触AChE的动物无法茁壮成长，大多数在成熟之前死亡。
Acetylcholinesterase (AChE) occurs in both asymmetric forms, covalently associated with a collagenous subunit called Q (ColQ), and globular forms that may be either soluble or membrane associated. At the skeletal neuromuscular junction, asymmetric AChE is anchored to the basal lamina of the synaptic cleft, where it hydrolyzes acetylcholine to terminate synaptic transmission. AChE has also been hypothesized to play developmental roles in the nervous system, and ColQ is also expressed in some AChE-poor tissues. To seek roles of ColQ and AChE at synapses and elsewhere, we generated ColQ-deficient mutant mice. ColQ −/− mice completely lacked asymmetric AChE in skeletal and cardiac muscles and brain; they also lacked asymmetric forms of the AChE homologue, butyrylcholinesterase. Thus, products of the ColQ gene are required for assembly of all detectable asymmetric AChE and butyrylcholinesterase. Surprisingly, globular AChE tetramers were also absent from neonatal ColQ −/− muscles, suggesting a role for the ColQ gene in assembly or stabilization of AChE forms that do not themselves contain a collagenous subunit. Histochemical, immunohistochemical, toxicological, and electrophysiological assays all indicated absence of AChE at ColQ −/− neuromuscular junctions. Nonetheless, neuromuscular function was initially robust, demonstrating that AChE and ColQ do not play obligatory roles in early phases of synaptogenesis. Moreover, because acute inhibition of synaptic AChE is fatal to normal animals, there must be compensatory mechanisms in the mutant that allow the synapse to function in the chronic absence of AChE. One structural mechanism appears to be a partial ensheathment of nerve terminals by Schwann cells. Compensation was incomplete, however, as animals lacking ColQ and synaptic AChE failed to thrive and most died before they reached maturity.