Mavlyutov Timur A, Nickells Robert W, Guo Lian-Wang
Department of Pharmacology, University of Wisconsin, School of Medicine and Public Health, Madison, WI 53706, USA.
Mol Vis. 2011 Apr 26;17:1034-43.
The sigma-1 receptor (σR1), a ligand-operated chaperone, has been inferred to be neuroprotective in previous studies using σR1 ligands. The σR1 specificity of the protective function, however, has yet to be firmly established, due to the existence of non-σR1 targets of the ligands. Here, we used the σR1-knockout mouse (Sigmar1(-/-)) to demonstrate unambiguously the role of the σR1 in protecting the retinal ganglion cells against degeneration after acute damage to the optic nerve.
Retinal σR binding sites were labeled with radioiodinated σR ligands and analyzed by autoradiography. Localization of the σR1 was performed by indirect immunofluorescence on frozen retinal sections. Retinal ganglion cell death was induced by acute optic nerve crush in wild-type and Sigmar1(-/-) mice. Surviving cells in the ganglion cell layer were counted on Nissl-stained retinal whole mounts 7 days after the crush surgery.
Photoaffinity labeling indicated the presence of the σR1 in the retina, in concentrations equivalent to those in liver tissue. Immunolabeling detected this receptor in cells of both the ganglion cell layer and the photoreceptor cell layer in wild-type retinas. Quantification of cells remaining after optic nerve crush showed that 86.8±7.9% cells remained in the wild-type ganglion cell layer, but only 68.3±3.4% survived in the Sigmar1(-/-), demonstrating a significant difference between the wild-type and the Sigmar1(-/-) in crush-induced ganglion cell loss.
Our data indicated faster retinal ganglion cell death in Sigmar1(-/-) than in wild-type mice under the stresses caused by optic nerve crush, providing direct evidence for a role of the σR1 in alleviating retinal degeneration. This conclusion is consistent with the previous pharmacological studies using σR1 agonists. Thus, our study supports the idea that the σR1 is a promising therapeutic target for neurodegenerative retinal diseases, such as glaucoma.
σ-1受体（σR1）是一种配体门控伴侣蛋白，在先前使用σR1配体的研究中已推断其具有神经保护作用。然而，由于配体存在非σR1靶点，保护功能的σR1特异性尚未得到确凿证实。在此，我们使用σR1基因敲除小鼠（Sigmar1(-/-)）明确证明σR1在保护视网膜神经节细胞免受视神经急性损伤后变性中的作用。
用放射性碘标记的σR配体标记视网膜σR结合位点，并通过放射自显影进行分析。通过对冷冻视网膜切片进行间接免疫荧光法确定σR1的定位。在野生型和Sigmar1(-/-)小鼠中通过急性视神经挤压诱导视网膜神经节细胞死亡。挤压手术后7天，在尼氏染色的视网膜全层标本上计数神经节细胞层中的存活细胞。
光亲和标记表明视网膜中存在σR1，其浓度与肝脏组织中的浓度相当。免疫标记在野生型视网膜的神经节细胞层和光感受器细胞层的细胞中均检测到该受体。视神经挤压后剩余细胞的定量分析表明，野生型神经节细胞层中86.8±7.9%的细胞存活，但在Sigmar1(-/-)小鼠中仅68.3±3.4%的细胞存活，这表明野生型和Sigmar1(-/-)小鼠在挤压诱导的神经节细胞损失方面存在显著差异。
我们的数据表明，在视神经挤压引起的应激下，Sigmar1(-/-)小鼠的视网膜神经节细胞死亡比野生型小鼠更快，这为σR1在减轻视网膜变性中的作用提供了直接证据。这一结论与先前使用σR1激动剂的药理学研究一致。因此，我们的研究支持σR1是神经退行性视网膜疾病（如青光眼）的一个有前景的治疗靶点这一观点。
