Neurosciences Group, Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford, UK.
J Neuromuscul Dis. 2018;5(2):231-240. doi: 10.3233/JND-170293.
Congenital myasthenic syndromes (CMS) are a group of inherited neuromuscular transmission disorders causing fatiguable muscle weakness. ADRB2 agonists have been observed to provide therapeutic benefit where destabilisation of NMJ structures is part of the underlying pathology, such as in DOK7, COLQ and MuSK CMS as well as in slow channel syndrome. However, very little is known about the molecular mechanisms underlying the effects of ADRB2 agonists in CMS.
In vitro investigation into whether an ADRB2 agonist affects the AChR clustering pathway and has the potential to increase the number and stability of AChR clusters.
Cultured C2C12 mouse myotubes overexpressing the common DOK7 frameshift mutation c.1124_1127dupTGCC were incubated with salbutamol sulphate and the effect on AChR cluster numbers were investigated. Moreover, agrin-induced AChR clusters in C2C12 WT cells were left to disperse after agrin-wash-off, and the effects of incubation with salbutamol sulphate on AChR cluster numbers were explored.
Salbutamol sulphate induced a significant increase in the number of AChR clusters formed on C2C12 cells overexpressing c.1124_1127dupTGCC. Furthermore, significantly more clusters remained in C2C12 WT myotubes incubated with salbutamol sulphate following agrin wash-off.
The results suggest that ADRB2 agonists directly affect proteins located at the neuromuscular junction and exert a stabilising effect on AChR clusters.
先天性肌无力综合征（CMS）是一组遗传性神经肌肉传递障碍，导致易疲劳性肌肉无力。ADRB2 激动剂已被观察到在 NMJ 结构不稳定的情况下提供治疗益处，例如在 DOK7、COLQ 和 MuSK CMS 以及慢通道综合征中。然而，对于 ADRB2 激动剂在 CMS 中的作用的分子机制知之甚少。
体外研究 ADRB2 激动剂是否影响 AChR 聚集途径，并具有增加 AChR 簇数量和稳定性的潜力。
培养过表达常见 DOK7 移码突变 c.1124_1127dupTGCC 的 C2C12 小鼠肌管，用硫酸沙丁胺醇孵育，并研究其对 AChR 簇数量的影响。此外，在 Agrin 洗脱后，让 Agrin 诱导的 C2C12 WT 细胞中的 AChR 簇分散，然后探索硫酸沙丁胺醇孵育对 AChR 簇数量的影响。
硫酸沙丁胺醇诱导过表达 c.1124_1127dupTGCC 的 C2C12 细胞形成的 AChR 簇数量显著增加。此外，在 Agrin 洗脱后用硫酸沙丁胺醇孵育的 C2C12 WT 肌管中，更多的簇仍然存在。
结果表明，ADRB2 激动剂直接影响位于神经肌肉接头的蛋白质，并对 AChR 簇发挥稳定作用。
