Laboratory of Biophysics Of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russia; Kazan State Medical University, Kazan, Russia; Open Laboratory of Neuropharmacology, Kazan Federal University, Kazan, Russia.
Laboratory of Biophysics Of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russia; Open Laboratory of Neuropharmacology, Kazan Federal University, Kazan, Russia.
Neuroscience. 2019 Apr 15;404:91-101. doi: 10.1016/j.neuroscience.2019.01.060. Epub 2019 Feb 8.
Septins (Sept) are highly conserved Guanosine-5'-triphosphate (GTP)-binding cytoskeletal proteins involved in neuronal signaling in the central nervous system but their involvement in signal transmission in peripheral synapses remains unclear. Sept5 and Sept9 proteins were detected in mouse peripheral neuromuscular junctions by immunofluorescence with a greater degree of co-localization with presynaptic than postsynaptic membranes. Preincubation of neuromuscular junction preparations with the inhibitor of Sept dynamics, forchlorfenuron (FCF), decreased co-localization of Sept with presynaptic membranes. FCF introduced ex vivo or in vivo had no effect on the amplitude of the spontaneous endplate currents (EPCs), indicating the absence of postsynaptic effects of FCF. However, FCF decreased acetylcholine (ACh) quantal release in response to nerve stimulation, reduced the amplitude of evoked quantal currents and decreased the number of quanta with long synaptic delays, demonstrating the presynaptic action of FCF. Nevertheless, FCF had no effect on the amplitude of calcium transient in nerve terminals, as detected by calcium-sensitive dye, and slightly decreased the ratio of the second response amplitude to the first one in paired-pulse experiments. These results suggest that FCF-induced decrease in ACh quantal secretion is not due to a decrease in Ca influx but is likely related to the impairment of later stages occurring after Ca entry, such as trafficking, docking or membrane fusion of synaptic vesicles. Therefore, Sept9 and Sept5 are abundantly expressed in presynaptic membranes, and disruption of Sept dynamics suppresses the evoked synchronous and delayed asynchronous quantal release of ACh, strongly suggesting an important role of Sept in the regulation of neurotransmission in peripheral synapses.
Septins (Sept) 是高度保守的鸟嘌呤-5'-三磷酸 (GTP) 结合细胞骨架蛋白，参与中枢神经系统的神经元信号传递，但它们在周围突触中的信号传递作用尚不清楚。通过免疫荧光，在小鼠周围神经肌肉接头中检测到 Sept5 和 Sept9 蛋白，它们与突触前膜的共定位程度大于与突触后膜的共定位程度。用 Sept 动力学抑制剂氟氯苯脲 (FCF) 预先孵育神经肌肉接头制剂，会减少 Sept 与突触前膜的共定位。FCF 体外或体内引入对自发性终板电流 (EPC) 的幅度没有影响，表明 FCF 没有突触后作用。然而，FCF 减少了对神经刺激的乙酰胆碱 (ACh) 量子释放，降低了诱发量子电流的幅度，并减少了长突触延迟的量子数量，证明了 FCF 的突触前作用。尽管如此，FCF 对神经末梢钙瞬变的幅度没有影响，如钙敏感染料所检测到的，并且在成对脉冲实验中，轻微降低了第二个响应幅度与第一个响应幅度的比值。这些结果表明，FCF 诱导的 ACh 量子分泌减少不是由于 Ca 流入减少引起的，而是可能与 Ca 进入后发生的后期阶段的损伤有关，例如突触囊泡的运输、对接或膜融合。因此，Sept9 和 Sept5 在突触前膜中大量表达，破坏 Sept 动力学会抑制诱发的同步和延迟异步 ACh 量子释放，强烈表明 Sept 在调节周围突触神经传递中起着重要作用。
