GRK1 and GRK7: Unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones
GRK1 and GRK7: Unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones
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DOI：
10.1111/j.1471-4159.2006.03920.x
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发表时间：
2006-08
影响因子：
4.7
通讯作者：
Yasutaka Wada;Junichi Sugiyama;T. Okano;Y. Fukada
中科院分区：
文献类型：
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作者：
Yasutaka Wada;Junichi Sugiyama;T. Okano;Y. Fukada
视网膜视锥细胞表现出独特的光反应，对光的敏感性更受抑制，关闭动力学比视杆细胞更快。为了理解这些视锥细胞反应特征的分子基础，我们专注于斑马鱼中由G蛋白偶联受体激酶（GRK）1和GRK 7启动的视蛋白失活过程，这是一种适合研究视网膜生理学和生物化学的动物模型。筛选出GRK 1（1A和1B）和GRK 7（7-1和7-2）的两个同源基因，并通过系统发育分析将其分为GRK亚家族1A、1B和7。原位杂交和免疫组织化学研究将GRK 1B和GRK 7 - 1定位于视锥外节，GRK 1A定位于视杆外节。视蛋白/GRKs的摩尔比估计在视杆中为569，在视锥中为153。重组GRKs磷酸化光激活视紫红质，主要视锥细胞亚型GRK 7 - 1的Vmax值是视杆细胞激酶GRK 1A的32倍。视锥激酶的增强的活性应提供视锥中光信号传导的增强的关闭机制，并通过降低信号放大效率而有助于视锥响应的特征。
Retinal cone cells exhibit distinctive photoresponse with a more restrained sensitivity to light and a more rapid shutoff kinetics than those of rods. To understand the molecular basis for these characteristics of cone responses, we focused on the opsin deactivation process initiated by G protein‐coupled receptor kinase (GRK) 1 and GRK7 in the zebrafish, an animal model suitable for studies on retinal physiology and biochemistry. Screening of the ocular cDNAs identified two homologs for each of GRK1 (1A and 1B) and GRK7 (7–1 and 7–2), and they were classified into three GRK subfamilies, 1 A, 1B and 7 by phylogenetic analysis. In situ hybridization and immunohistochemical studies localized both GRK1B and GRK7‐1 in the cone outer segments and GRK1A in the rod outer segments. The opsin/GRKs molar ratio was estimated to be 569 in the rod and 153 in the cone. The recombinant GRKs phosphorylated light‐activated rhodopsin, and the Vmax value of the major cone subtype, GRK7‐1, was 32‐fold higher than that of the rod kinase, GRK1A. The reinforced activity of the cone kinase should provide a strengthened shutoff mechanism of the light‐signaling in the cone and contribute to the characteristics of the cone responses by reducing signal amplification efficiency.