Cone deactivation kinetics and GRK1/GRK7 expression in enhanced S cone syndrome caused by mutations in NR2E3
Cone deactivation kinetics and GRK1/GRK7 expression in enhanced S cone syndrome caused by mutations in NR2E3
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DOI：
10.1167/iovs.02-0494
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发表时间：
2003-03-01
影响因子：
4.4
通讯作者：
Milam, AH
中科院分区：
文献类型：
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作者：
Cideciyan, AV;Jacobson, SG;Milam, AH
目的.目的探讨NR 2 E3突变引起的S锥增强综合征（ESCS）患者视锥失活动力学与G蛋白偶联受体激酶1（GRK 1）和GRK 7免疫反应性的关系。采用视锥细胞光转导模型，利用视网膜电图（ERG）研究视锥细胞的激活动力学。使用配对闪光ERG范式定量了明亮闪光后视锥细胞的失活动力学。用抗视锥蛋白和激酶GRK 1和GRK 7的抗体在死后正常和ESCS视网膜组织中进行免疫细胞化学。ESCS患者中长/中波长敏感（L/M）视锥细胞介导的反应的激活动力学与正常L/M视锥细胞的激活动力学相似。ESCS短波长敏感（S）视锥细胞的激活动力学，当与相同刺激诱发的正常L/M视锥细胞反应相比时，慢了与光谱敏感性的预期差异一致的量。明亮的闪光后，选择唤起相同的激活动力学，ESCS S锥失活慢得多ESCS或正常的L/M锥。正常人视网膜显示强烈标记的锥外段与抗GRK 1和抗GRK 7。在ESCS视网膜中，L/M视蛋白阳性的外段用抗GRK 1强烈标记，而S视蛋白阳性的外段没有显示出可检测的GRK 1反应性。GRK 7标记在ESCS视网膜的所有光感受器中均不存在。NR 2 E3突变导致的视锥细胞占主导地位的人类视网膜提供了对GRK 1和GRK 7在人类视锥细胞光感受器中的生理作用的更多理解。当GRK 1存在于ESCS中时，人L/M视锥细胞中的正常失活动力学可以在没有GRK 7的情况下发生，但是当GRK 7存在但GRK 1缺乏时，不会发生在Oguchi病中。缺乏GRK 1和GRK 7的ESCS患者的S锥中的失活动力学的结果在一个更明显的异常，并建议存在部分补偿时，另一个GRK是不足的。
PURPOSE. To determine the relationship between cone deactivation kinetics in patients with the enhanced S cone syndrome (ESCS) caused by mutations in NR2E3 and the immunoreactivity to G-protein-coupled receptor kinase 1 (GRK1) and GRK7.METHODS. Electroretinogram (ERG) photoresponses were used to investigate activation kinetics of cones with a model of cone phototransduction. Deactivation kinetics of cones after bright flashes was quantified with a paired-flash ERG paradigm. Immunocytochemistry was performed with antibodies against cone opsins and kinases GRK1 and GRK7 in postmortem normal and ESCS retinal tissue.RESULTS. Activation kinetics of long/middle-wavelength-sensitive (L/M) cone-mediated responses in patients with ESCS were similar to those of normal L/M cones. Activation kinetics of ESCS short-wavelength-sensitive (S) cones, when compared with normal L/M cone responses evoked by the same stimulus, were slower by an amount consistent with the expected differences in spectral sensitivities. After bright flashes chosen to evoke identical activation kinetics, ESCS S cones deactivated much more slowly than ESCS or normal L/M cones. Normal human retina revealed strongly labeled cone outer segments with anti-GRK1 and anti-GRK7. In an ESCS retina, outer segments positive for L/M opsin were strongly labeled with anti-GRK1, whereas outer segments positive for S opsin showed no detectable GRK1 reactivity. GRK7 labeling was absent in all photoreceptors of the ESCS retina.CONCLUSIONS. The cone-dominant human retina resulting from NR2E3 mutations affords greater understanding of the physiological roles of GRK1 and GRK7 in human cone photo-receptors. Normal deactivation kinetics in human L/M cones can occur without GRK7 when GRK1 is present in ESCS, but does not occur when GRK7 is present but GRK1 is deficient in Oguchi disease. Lack of both GRK1 and GRK7 in S cones of patients with ESCS results in a more pronounced abnormality in deactivation kinetics and suggests the existence of partial compensation by either GRK when the other is deficient.