Pattnaik B, Jellali A, Sahel J, Dreyfus H, Picaud S
Laboratoire de Physiopathologie Cellulaire et Moléculaire de la Rétine, Institut National de la Santé et de la Recherche Médicale EMI 99-18, University Louis Pasteur, 67091 Strasbourg Cedex, France.
J Neurosci. 2000 Sep 15;20(18):6789-96. doi: 10.1523/JNEUROSCI.20-18-06789.2000.
Protein MAP1B was recently reported to link GABA(C) receptors to the cytoskeleton at neuronal synapses. This interaction was demonstrated in the mammalian retina, where GABA(C) receptors were thought to be exclusively expressed in bipolar cells. Our previous studies on cultured photoreceptors suggested however the presence of GABA(C) receptors in cones. To further investigate GABA(C) receptor expression in cones, we measured GABA responses in mammalian photoreceptors in situ, and we examined the distribution of the receptor and that of protein MAP1B in the mammalian outer retina. Photoreceptors were recorded from flat-mounted retinas of retinal degeneration mice at an age when the retina becomes cone-dominated after rod cell death. GABA(A) and GABA(C)-gated currents were produced only in cones but not rods. Recording freshly dissociated retinal cells from wild-type C57 mice confirmed the presence of GABA(A) and GABA(C) receptors in cones. Immunohistochemical labeling of mouse and rat retinal sections localized GABA(C) receptors to cone terminals that were identified by peanut agglutinin lectin staining. As expected from previous studies on bipolar cells, the punctate immunostaining was not restricted to cone terminals in the outer plexiform layer. MAP1B immunolabeling was obtained in rat and pig retinas and was similarly found in cone terminals identified by the peanut agglutinin lectin staining. These results provide physiological and histological evidence that cones receive a GABA feedback in the mammalian retina and are consistent with the notion that protein MAP1B links GABA(C) receptors to the cytoskeleton at postsynaptic sites.
最近有报道称，蛋白质MAP1B在神经元突触处将GABA(C)受体与细胞骨架连接起来。这种相互作用在哺乳动物视网膜中得到了证实，在那里GABA(C)受体被认为仅在双极细胞中表达。然而，我们之前对培养的光感受器的研究表明，视锥细胞中存在GABA(C)受体。为了进一步研究视锥细胞中GABA(C)受体的表达情况，我们原位测量了哺乳动物光感受器中的GABA反应，并检测了该受体以及蛋白质MAP1B在哺乳动物视网膜外层的分布。在视网膜变性小鼠的扁平视网膜上记录光感受器，这些小鼠在杆状细胞死亡后视网膜以视锥细胞为主导的年龄阶段。GABA(A)和GABA(C)门控电流仅在视锥细胞中产生，而在杆状细胞中未产生。从野生型C57小鼠新鲜分离的视网膜细胞记录结果证实了视锥细胞中存在GABA(A)和GABA(C)受体。对小鼠和大鼠视网膜切片进行免疫组织化学标记，将GABA(C)受体定位到通过花生凝集素凝集素染色鉴定的视锥细胞终末。正如之前对双极细胞的研究所预期的那样，点状免疫染色并不局限于外网状层的视锥细胞终末。在大鼠和猪的视网膜中获得了MAP1B免疫标记，并且同样在通过花生凝集素凝集素染色鉴定的视锥细胞终末中发现。这些结果提供了生理学和组织学证据，表明视锥细胞在哺乳动物视网膜中接受GABA反馈，并且与蛋白质MAP1B在突触后位点将GABA(C)受体与细胞骨架连接起来的观点一致。
