Dick O, Hack I, Altrock W D, Garner C C, Gundelfinger E D, Brandstätter J H
Abteilung für Neuroanatomie, Max-Planck-Institut für Hirnforschung, D-60528 Frankfurt am Main, Germany.
J Comp Neurol. 2001 Oct 15;439(2):224-34. doi: 10.1002/cne.1344.
In recent years significant progress has been made in the elucidation of the molecular assembly of the postsynaptic density at synapses, whereas little is known as yet about the components of the presynaptic active zone. Piccolo and Bassoon, two structurally related presynaptic cytomatrix proteins, are highly concentrated at the active zones of both excitatory and inhibitory synapses in rat brain. In this study we used immunocytochemistry to examine the cellular and ultrastructural localization of Piccolo at synapses in the rat retina and compared it with that of Bassoon. Both proteins showed strong punctate immunofluorescence in the outer and the inner plexiform layers of the retina. They were found presynaptically at glutamatergic ribbon synapses and at conventional GABAergic and glycinergic synapses. Although the two proteins were coexpressed at all photoreceptor ribbon synapses and at some conventional amacrine cell synapses, at bipolar cell ribbon synapses only Piccolo was present. Our data demonstrate similarities but also differences in the molecular composition of the presynaptic apparatuses of the synapses in the retina, differences that may account for the functional differences observed between the ribbon and the conventional amacrine cell synapses and between the photoreceptor and the bipolar cell ribbon synapses in the retina.
近年来，在阐明突触后致密区的分子组装方面取得了重大进展，而对于突触前活性区的组成成分，人们目前还知之甚少。 piccolo和Bassoon是两种结构相关的突触前细胞基质蛋白，在大鼠脑内的兴奋性和抑制性突触的活性区均高度富集。在本研究中，我们运用免疫细胞化学方法检测了piccolo在大鼠视网膜突触处的细胞及超微结构定位，并将其与Bassoon的定位进行了比较。这两种蛋白在视网膜的外丛状层和内丛状层均呈现出强烈的点状免疫荧光。它们定位于突触前的谷氨酸能带状突触以及传统的γ-氨基丁酸能和甘氨酸能突触。尽管这两种蛋白在所有光感受器带状突触和一些传统无长突细胞突触中共同表达，但在双极细胞带状突触中仅存在piccolo。我们的数据表明，视网膜中突触前装置的分子组成既有相似之处，也存在差异，这些差异可能解释了视网膜中带状突触与传统无长突细胞突触之间以及光感受器与双极细胞带状突触之间所观察到的功能差异。
