Gábriel Robert, de Souza Sunita, Ziff Edward B, Witkovsky Paul
Department of General Zoology and Neurobiology, University of Pécs, H-7604 Pécs, Hungary.
J Comp Neurol. 2002 Jul 22;449(2):129-40. doi: 10.1002/cne.10280.
We used specific antibodies against two postsynaptic density proteins, GRIP (glutamate receptor interacting protein) and ABP (AMPA receptor-binding protein), to study their distribution in the rat retina. In the central nervous system, it has been shown that both proteins bind strongly to the AMPA glutamate receptor (GluR) 2/3 subunits, but not other GluRs, through a set of three PDZ domains. Western blots detected a single GRIP protein that was virtually identical in retina and brain, whereas retinal ABP corresponded to only one of three ABP peptides found in brain. The retinal distributions of GluR2/3, GRIP, and ABP immunoreactivity (IR) were similar but not identical. GluR2/3 immunoreactivity (IR) was abundant in both plexiform layers and in large perikarya. ABP IR was concentrated in large perikarya but was sparse in the plexiform layers, whereas GRIP IR was relatively more abundant in the plexiform layers than in perikarya. Immunolabel for these three antibodies consisted of puncta < or = 0.2 microm in diameter. The cellular localization of GRIP and ABP IR was examined by double labeling subclasses of retinal neuron with characteristic marker proteins, e.g., calbindin. GRIP, ABP, and GluR2/3 IR were detected in horizontal cells, dopaminergic and glycinergic AII amacrine cells and large ganglion cells. Immunolabel was absent in rod bipolar and weak or absent in cholinergic amacrine cells. By using the tyramide method of signal amplification, a colocalization of GluR2/3 was found with either GRIP or ABP in horizontal cell terminals, and perikarya of amacrine and ganglion cells. Our results show that ABP and GRIP colocalize with GluR2/3 in particular subsets of retinal neuron, as was previously established for certain neurons in the brain.
我们使用针对两种突触后致密蛋白——GRIP（谷氨酸受体相互作用蛋白）和ABP（AMPA受体结合蛋白）的特异性抗体，来研究它们在大鼠视网膜中的分布。在中枢神经系统中，已表明这两种蛋白通过一组三个PDZ结构域与AMPA谷氨酸受体（GluR）2/3亚基强烈结合，但不与其他GluR结合。蛋白质印迹法检测到视网膜和大脑中几乎相同的单一GRIP蛋白，而视网膜ABP仅对应于大脑中发现的三种ABP肽中的一种。GluR2/3、GRIP和ABP免疫反应性（IR）在视网膜中的分布相似但不完全相同。GluR2/3免疫反应性（IR）在两个神经毡层和大型核周体中都很丰富。ABP IR集中在大型核周体中，但在神经毡层中稀疏，而GRIP IR在神经毡层中相对比在核周体中更丰富。这三种抗体的免疫标记由直径小于或等于0.2微米的小点组成。通过用特征性标记蛋白（如钙结合蛋白）对视网膜神经元亚类进行双重标记，研究了GRIP和ABP IR的细胞定位。在水平细胞、多巴胺能和甘氨酸能AII无长突细胞以及大型神经节细胞中检测到GRIP、ABP和GluR2/3 IR。在视杆双极细胞中未检测到免疫标记，在胆碱能无长突细胞中免疫标记较弱或未检测到。通过使用酪胺信号放大法，发现在水平细胞终末以及无长突细胞和神经节细胞的核周体中，GluR2/3与GRIP或ABP共定位。我们的结果表明，ABP和GRIP与GluR2/3在视网膜神经元的特定亚群中共定位，这与先前在大脑某些神经元中所确定的情况相同。
