Institute of Genetic Medicine, The John Walton Muscular Dystrophy Research Centre, Newcastle University, International Centre for Life, Newcastle Upon Tyne NE1 3BZ, UK.
Tissue Omics Project Group, Biomedical Research Department, Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V., 44227 Dortmund, Germany.
Hum Mol Genet. 2018 May 1;27(9):1556-1564. doi: 10.1093/hmg/ddy062.
Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of disorders, termed congenital myasthenic syndromes (CMS). Therapies acting on the sympathetic nervous system, including the selective β2 adrenergic agonist salbutamol and the α and β adrenergic agonist ephedrine, have become standard treatment for several types of CMS. However, the mechanism of the therapeutic effect of sympathomimetics in these disorders is not understood. Here, we examined the effect of salbutamol on NMJ development using zebrafish with deficiency of the key postsynaptic proteins Dok-7 and MuSK. Treatment with salbutamol reduced motility defects in zebrafish embryos and larvae. In addition, salbutamol lead to morphological improvement of postsynaptic acetycholine receptor (AChR) clustering and size of synaptic contacts in Dok-7-deficient zebrafish. In MuSK-deficient zebrafish, salbutamol treatment reduced motor axon pathfinding defects and partially restored the formation of aneural prepatterned AChRs. In addition, the effects of salbutamol treatment were prevented by pre-treatment with a selective β2 antagonist. Treatment with the cyclic adenosine monophosphate (cAMP) activator forskolin, replicated the effects of salbutamol treatment. These results suggest that sympathomimetics exert a direct effect on neuromuscular synaptogenesis and do so via β2 adrenoceptors and via a cAMP-dependent pathway.
神经肌肉接头（NMJ）的遗传缺陷包括越来越多样化的疾病，称为先天性肌无力综合征（CMS）。作用于交感神经系统的治疗方法，包括选择性β2 肾上腺素能激动剂沙丁胺醇和α和β肾上腺素能激动剂麻黄碱，已成为几种 CMS 的标准治疗方法。然而，这些疾病中拟交感神经药物治疗效果的机制尚不清楚。在这里，我们使用缺乏关键突触后蛋白 Dok-7 和 MuSK 的斑马鱼研究了沙丁胺醇对 NMJ 发育的影响。沙丁胺醇处理可减少斑马鱼胚胎和幼虫的运动缺陷。此外，沙丁胺醇导致 Dok-7 缺陷的斑马鱼中突触后乙酰胆碱受体（AChR）聚集和突触接触大小的形态改善。在 MuSK 缺陷的斑马鱼中，沙丁胺醇处理可减少运动轴突寻径缺陷，并部分恢复无神经预先形成的 AChR 的形成。此外，β2 受体选择性拮抗剂的预处理可预防沙丁胺醇处理的作用。环磷酸腺苷（cAMP）激活剂 forskolin 的处理复制了沙丁胺醇处理的效果。这些结果表明，拟交感神经药物对神经肌肉突触发生有直接作用，通过β2 肾上腺素能受体和 cAMP 依赖性途径发挥作用。
