The Drosophila TMEM184B ortholog Tmep ensures proper locomotion by restraining ectopic firing at the neuromuscular junction
The Drosophila TMEM184B ortholog Tmep ensures proper locomotion by restraining ectopic firing at the neuromuscular junction
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DOI：
10.1101/2021.09.11.459917
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Tiffany S. Cho;Eglė Beigaitė;Nathaniel E. Klein;S. Sweeney;Martha R. C. Bhattacharya
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文献类型：
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作者：
Tiffany S. Cho;Eglė Beigaitė;Nathaniel E. Klein;S. Sweeney;Martha R. C. Bhattacharya
TMEM184B被认为是一种促进损伤后轴突变性的七通道膜蛋白。TMEM184B突变导致小鼠神经肌肉结构异常以及感觉和运动行为缺陷。TMEM184B引起神经肌肉缺陷的机制尚不清楚。我们利用黑腹果蝇研究了TMEM184B同源基因Tmep （CG12004）在神经肌肉连接处的功能。我们发现Tmep是成虫完全生存能力和幼虫有效运动所必需的。与对照组相比，Tmep突变幼虫的身体收缩率降低，雌性的缺陷更大。幸存的成年Tmep突变雌性表现出“爆炸敏感性”，这是一种与癫痫发作相关的表型。在体壁肌肉的记录中，Tmep突变体表现出明显的高兴奋性，对单一刺激产生许多突触后电位，这与Tmep在抑制突触兴奋性中的作用一致。Tmep突变体的神经肌肉连接显示出适度的结构缺陷和卫星钮扣，这也可能导致运动表现不佳。Tmep在运动神经元内的核内体和突触囊泡中表达，提示其可能在突触膜运输中起作用。通过RNAi敲除，我们发现Tmep是运动神经元中正常的幼虫运动和兴奋性所必需的。运动缺陷可以通过突触前破坏内质网钙通道或减少诱发释放概率来修复，这表明突触活动过度驱动行为缺陷。我们的工作建立了TMEM184B同源Tmep在突触传递和运动行为调节中的关键功能。
TMEM184B is a putative seven-pass membrane protein that promotes axon degeneration after injury. TMEM184B mutation causes aberrant neuromuscular architecture and sensory and motor behavioral defects in mice. The mechanism through which TMEM184B causes neuromuscular defects is unknown. We employed Drosophila melanogaster to investigate the function of the TMEM184B ortholog, Tmep (CG12004) at the neuromuscular junction. We show that Tmep is required for full adult viability and efficient larval locomotion. Tmep mutant larvae have a reduced body contraction rate compared to controls, with stronger deficits in females. Surviving adult Tmep mutant females show “bang sensitivity,” a phenotype associated with epileptic seizures. In recordings from body wall muscles, Tmep mutants show substantial hyperexcitability, with many post-synaptic potentials fired in response to a single stimulation, consistent with a role for Tmep in restraining synaptic excitability. Neuromuscular junctions in Tmep mutants show modest structural defects and satellite boutons, which could also contribute to poor locomotor performance. Tmep is expressed in endosomes and synaptic vesicles within motor neurons, suggesting a possible role in synaptic membrane trafficking. Using RNAi knockdown, we show that Tmep is required in motor neurons for proper larval locomotion and excitability. Locomotor defects can be rescued by presynaptic knock-down of endoplasmic reticulum calcium channels or by reducing evoked release probability, suggesting that excess synaptic activity drives behavioral deficiencies. Our work establishes a critical function for the TMEM184B ortholog Tmep in the regulation of synaptic transmission and locomotor behavior.