Bajjalieh S M, Frantz G D, Weimann J M, McConnell S K, Scheller R H
Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University, California 94305.
J Neurosci. 1994 Sep;14(9):5223-35. doi: 10.1523/JNEUROSCI.14-09-05223.1994.
The synaptic vesicle proteins SV2A and SV2B (SV2 = synaptic vesicle protein 2) are two highly related proteins belonging to a family of transporters. As a first step toward identifying the function of the SV2 proteins, we examined the expression of SV2A and SV2B in the rat brain by in situ hybridization, immunohistochemistry, and immunoprecipitation with isoform-specific antibodies. These analyses revealed that one isoform, SV2A, is expressed ubiquitously throughout the brain at varying levels. The other isoform, SV2B, has a more limited distribution with varying degrees of coexpression with SV2A. Immunoprecipitation of brain synaptic vesicles with isoform-specific antibodies followed by Western analyses suggests that both isoforms can be present on the same synaptic vesicle. The expression of the SV2 proteins did not correlate either with neurotransmitter phenotype or with the expression of other synaptic vesicle protein isoforms. SV2B expression was observed to change during development; it is more widely expressed in the immature brain and is found in cells that have yet to establish synaptic contacts. The ubiquitous and overlapping expression of the SV2s suggests that they perform a function common to all synaptic vesicles. Variable and changing coexpression of the SV2 isoforms may indicate that SV2 function is regulated by the isoform composition of synaptic vesicles. The observation that the synaptic vesicle proteins, all occurring in multiple isoforms, are differentially expressed with respect to each other indicates that up to 90 different vesicle types are possible.
突触囊泡蛋白SV2A和SV2B（SV2 = 突触囊泡蛋白2）是属于转运蛋白家族的两种高度相关的蛋白质。作为确定SV2蛋白功能的第一步，我们通过原位杂交、免疫组织化学以及使用亚型特异性抗体进行免疫沉淀，研究了SV2A和SV2B在大鼠脑中的表达。这些分析表明，一种亚型SV2A在整个大脑中普遍表达，但水平各异。另一种亚型SV2B的分布更为局限，与SV2A存在不同程度的共表达。用亚型特异性抗体对脑突触囊泡进行免疫沉淀，随后进行蛋白质印迹分析，结果表明两种亚型都可能存在于同一突触囊泡上。SV2蛋白的表达与神经递质表型或其他突触囊泡蛋白亚型的表达均无关联。观察到SV2B的表达在发育过程中发生变化；它在未成熟大脑中表达更为广泛，且存在于尚未建立突触联系的细胞中。SV2的普遍且重叠的表达表明它们执行所有突触囊泡共有的功能。SV2亚型的可变且不断变化的共表达可能表明SV2的功能受突触囊泡亚型组成的调节。观察到所有以多种亚型形式存在的突触囊泡蛋白彼此差异表达，这表明可能存在多达90种不同的囊泡类型。
