Brandstätter J H, Fletcher E L, Garner C C, Gundelfinger E D, Wässle H
Max-Planck-Institut für Hirnforschung, Abteilung für Neuroanatomie, Frankfurt am Main, Germany.
Eur J Neurosci. 1999 Oct;11(10):3683-93. doi: 10.1046/j.1460-9568.1999.00793.x.
Bassoon is a 420-kDa presynaptic protein which is highly concentrated at the active zones of nerve terminals of conventional synapses, both excitatory glutamatergic and inhibitory GABAergic, in rat brain. It is thought to be involved in the organization of the cytomatrix at the site of neurotransmitter release. In the retina, there are two structurally and functionally distinct types of synapses: ribbon and conventional synapses. Antibodies against bassoon were applied to sections of rat and rabbit retina. Strong punctate immunofluorescence was found in the outer and inner plexiform layers. Using pre- and post-embedding immunostaining and electron microscopy, bassoon was localized in the outer plexiform layer at ribbon synapses formed by rods and cones but was absent from basal synaptic contacts formed by cones. In the inner plexiform layer a different picture emerged. As in the brain, bassoon was found at conventional inhibitory GABAergic synapses, made by amacrine cells, but it was absent from the bipolar cell ribbon synapses. These data demonstrate differences in the molecular composition of the presynaptic apparatuses of outer and inner plexiform layer ribbon synapses. Thus, differential equipment with cytomatrix proteins may account for the functional differences observed between the two types of ribbon synapses in the retina.
巴松管蛋白是一种420 kDa的突触前蛋白，在大鼠脑内传统突触（包括兴奋性谷氨酸能突触和抑制性γ-氨基丁酸能突触）的神经末梢活性区高度富集。它被认为参与了神经递质释放部位细胞基质的组织。在视网膜中，存在两种结构和功能不同的突触：带状突触和传统突触。将抗巴松管蛋白的抗体应用于大鼠和兔视网膜切片。在外丛状层和内丛状层发现了强烈的点状免疫荧光。通过包埋前和包埋后免疫染色及电子显微镜观察，巴松管蛋白定位于由视杆和视锥形成的带状突触所在的外丛状层，但在视锥形成的基底突触接触处未发现。在内丛状层则呈现出不同的情况。与在脑中一样，在由无长突细胞形成的传统抑制性γ-氨基丁酸能突触处发现了巴松管蛋白，但在双极细胞带状突触处未发现。这些数据表明外丛状层和内丛状层带状突触的突触前装置分子组成存在差异。因此，细胞基质蛋白的差异配备可能解释了视网膜中两种类型带状突触之间观察到的功能差异。
