Teichberg S, Holtzman E, Crain S M, Peterson E R
J Cell Biol. 1975 Oct;67(1):215-30. doi: 10.1083/jcb.67.1.215.
Intact neurons in cultures of fetal rodent spinal cord explants show stimulation-dependent uptake of horseradish peroxidase (HRP) into many small vesicles and occasional tubules and multivesicular bodies (MVB) at presynaptic terminals. Presynaptic terminals were allowed to take up HRP during 1 h of strychnine-enhanced stimulation of synaptic transmitter release and then "chased" in tracer-free medium either with strychnine or with 10 mM Mg++ which depresses transmitter release. Tracer-containing vesicles are lost from terminals under both chase conditions; the loss is more rapid (4-8 h) with strychnine than with 10 mM Mg++ (8-16 h). There is a parallel decrease in the numbers of labeled MVB's at terminals. Loss of tracer with 10 mM Mg++ does not appear to be due to the membrane rearrangements (exocytosis coupled to endocytosis) that presumably lead to initial tracer uptake; terminals exposed to HRP and Mg++ for up to 16 h show little tracer uptake into vesicles. Nor is the decrease likely to the due to loss of HRP enzyme activity; HRP is very stable in solution. During the chases there is a striking accumulation of HRP in perikarya that is far more extensive in cultures initially exposed to tracer with strychnine than 10 mM Mg++ regardless of chase conditions. Much of the tracer ends up in large dense bodies. These findings suggest that synaptic vesicle membrane turnover involves retrograde axonal transport of membrane to neuronal perikarya for further processing, including lysosomal degradation. The more rapid (4-8 h) loss of tracer-containing vesicles with strychnine may reflect vesicle membrane reutilization for exocytosis.
在胎鼠脊髓外植体培养物中，完整的神经元显示，在突触前终末，辣根过氧化物酶（HRP）可依赖刺激被摄取到许多小囊泡以及偶尔出现的小管和多泡体（MVB）中。在士的宁增强突触递质释放刺激1小时期间，允许突触前终末摄取HRP，然后在无示踪剂的培养基中“追踪”，分别加入士的宁或10 mM Mg++，后者可抑制递质释放。在两种追踪条件下，含有示踪剂的囊泡均从终末丢失；士的宁处理时丢失更快（4 - 8小时），而10 mM Mg++处理时则为8 - 16小时。终末处标记的MVB数量也相应减少。10 mM Mg++导致的示踪剂丢失似乎并非由于可能导致最初示踪剂摄取的膜重排（与胞吞作用偶联的胞吐作用）；暴露于HRP和Mg++长达16小时的终末几乎没有示踪剂摄取到囊泡中。减少也不太可能是由于HRP酶活性丧失；HRP在溶液中非常稳定。在追踪期间，HRP在胞体中显著积聚，无论追踪条件如何，最初用士的宁而非10 mM Mg++处理示踪剂的培养物中积聚更为广泛。许多示踪剂最终进入大的致密体中。这些发现表明，突触囊泡膜更新涉及膜向神经元胞体的逆行轴突运输，以便进行进一步处理，包括溶酶体降解。士的宁处理时含有示踪剂的囊泡更快（4 - 8小时）丢失可能反映了囊泡膜用于胞吐作用的再利用。
