突触囊泡膜蛋白及神经多肽的神经内动力学

神经递质的释放是一复杂的过程，它受若干种囊泡胰蛋白和突触前膜蛋白的调控、本文综述了作者近年来对两类突触囊泡膜蛋白和神经多肽在大鼠坐骨神经内的转运及分布。坐骨神经在结扎以后，正常转运中的各种蛋白及多肽便积聚于结扎的近侧端（表示该物质从周围内细胞体转运）。囊泡膜镶嵌蛋白（Ｓｙｎａｐｔｏｐｈｙｓｉｎ，ＳＶ２，ＳｙｎａｐｔｏｌａｇａｉｎⅠ和ＳｙｎａｎｔｏｂｒｅｖｉｎⅡ）和表面粘附囊泡膜蛋白（ＳｙｎａｐｓｉｎⅠ，Ｒｅｂ３ａ与Ｒａｂｎｈｉｌｉｎ－３Ａ）在神经结扎后一小时即可在结扎的近侧端被检测到，其后，随着时间的延长（至八小时），积聚量不断增加，说明该二类蛋白被快相转运。但是５０％～８０％的囊泡镶嵌蛋白同时积聚在结扎处的远侧端，仅１０％～３０％的表面粘附膜蛋白积肥聚在结扎的远侧端，显示绝大部分表面粘附膜蛋白在神经终末被解，而大部分囊泡膜镶嵌蛋白参于蛋白的再循环。除此之外，本文还研究了神经多肽在周围神经内的转运．位于致密核心囊泡内的神经多肽快速从细胞体向周围转运。但仍有３０％～４０％的神经多肽积聚于结扎处的远侧端，参与再循环．本文显示囊泡膜镶嵌蛋白、表面粘附膜蛋白以及神经多肽各有其独特的神经内转运模式。

AXONAL TRANSPORT AND INTRANEURONAL DYNAMICS OF SYNAPTIC VESICLE PROTEINS AND NEUROPEPTIDE ORGANELLES IN NEURONS

Neurotransmitter release is controlled by groups of ptoteins associated with the meinbran of synapticvesicles and the presynaptic membrane. The intraneuronal dynamics and distribution of organelle-bound substanceswere investigated using biochemical and immunocytochemical methods. The sciatic nerve and the spinal roots ofadult rats were Crushed in order to interrupt the fast axonal transport of organelle-bough substances, resulting inaccumulations of transported material proximal and distal to the crushes.A fier indirect immuno-labelling, distinct accumulations of the transmembtane synaptic vesicle proteins synaptophysin, synaptobrevin Ⅱ, synaptotagmin Ⅰand SV2 were observed proximal and distal to the crushes as early as 1h after operation, demonstrating that these proteins were carried with fast axonal transport. Analysis usingcytofluorimetric scanning showed that accumulated amounts of these proteins increased markedly with time andthat 50%～80% of the anterogradely transported substances were recycled. Furthermore, the surface adsorbedproteins synapsin Ⅰ, Rab3a and rabphilin-3A accumulated linearly proximal to the crush. The ratio between distaland proximal accumulations was 30% for synapsin Ⅰ and 10% for Rab3a and rabphilin-3A. Consistent results fromimmunoblot and immuno-EM experiments were obtained, indicating that surface adsorbed proteins, after arrival atthe nerve terminals, are degraded or structurally modified at the end of their lifespan in the presynapse, while thetransmembrane proteins are largely recycled. Neuropeptides, stored in large dense cored vesicle, accumulated onthe proximal side, but comparatively small amounts (30%～40% ) were recycling. The results indicate that transmembrane and surface adsorbed synaptic vesicle proteins, as well as neuropeptides, demonstrate distinct patternsin intraneuronal trafficking.