David Sandeep, Pinter Katherine, Nguyen Keziah-Khue, Lee David S, Lei Zhengchang, Sokolova Yuliya, Sheets Lavinia, Kindt Katie S
Section on Sensory Cell Development and Function, National Institute on Deafness and other Communication Disorders, Bethesda, MD, USA.
National Institutes of Health-Brown University Graduate Partnership Program, Bethesda, MD, USA.
bioRxiv. 2024 May 20:2024.05.20.595037. doi: 10.1101/2024.05.20.595037.
Sensory hair cells of the inner ear utilize specialized ribbon synapses to transmit sensory stimuli to the central nervous system. This sensory transmission necessitates rapid and sustained neurotransmitter release, which relies on a large pool of synaptic vesicles at the hair-cell presynapse. Work in neurons has shown that kinesin motor proteins traffic synaptic material along microtubules to the presynapse, but how new synaptic material reaches the presynapse in hair cells is not known. We show that the kinesin motor protein Kif1a and an intact microtubule network are necessary to enrich synaptic vesicles at the presynapse in hair cells. We use genetics and pharmacology to disrupt Kif1a function and impair microtubule networks in hair cells of the zebrafish lateral-line system. We find that these manipulations decrease synaptic-vesicle populations at the presynapse in hair cells. Using electron microscopy, along with calcium imaging and electrophysiology, we show that a diminished supply of synaptic vesicles adversely affects ribbon-synapse function. mutants exhibit dramatic reductions in spontaneous vesicle release and evoked postsynaptic calcium responses. Additionally, we find that mutants exhibit impaired rheotaxis, a behavior reliant on the ability of hair cells in the lateral line to respond to sustained flow stimuli. Overall, our results demonstrate that Kif1a-based microtubule transport is critical to enrich synaptic vesicles at the active zone in hair cells, a process that is vital for proper ribbon-synapse function.
内耳的感觉毛细胞利用特殊的带状突触将感觉刺激传递到中枢神经系统。这种感觉传递需要快速且持续的神经递质释放，这依赖于毛细胞突触前膜处大量的突触小泡。在神经元中的研究表明，驱动蛋白运动蛋白沿着微管将突触物质运输到突触前膜，但新的突触物质如何到达毛细胞的突触前膜尚不清楚。我们发现，驱动蛋白运动蛋白Kif1a和完整的微管网络对于在毛细胞的突触前膜富集突触小泡是必需的。我们利用遗传学和药理学方法破坏斑马鱼侧线系统毛细胞中Kif1a的功能并损害微管网络。我们发现这些操作会减少毛细胞突触前膜处的突触小泡数量。通过电子显微镜、钙成像和电生理学方法，我们表明突触小泡供应减少会对带状突触功能产生不利影响。突变体表现出自发小泡释放和诱发的突触后钙反应显著降低。此外，我们发现突变体表现出趋流性受损，这种行为依赖于侧线中的毛细胞对持续流动刺激作出反应的能力。总体而言，我们的结果表明，基于Kif1a的微管运输对于在毛细胞的活跃区富集突触小泡至关重要，这一过程对于正常的带状突触功能至关重要。
