Changes in the intracellular Ca2+ concentration regulate the visual signal transduction cascade directly or more often indirectly through Ca2+-binding proteins. Here we focus on centrins, which are members of a highly conserved subgroup of the EF-hand superfamily of Ca2+-binding proteins in photoreceptor cells of the vertebrate retina. Centrins are commonly associated with centrosome-related structures. In mammalian retinal photoreceptor cells, four centrin isoforms are expressed as prominent components in the connecting cilium linking the light-sensitive outer segment compartment with the metabolically active inner segment compartment. Our data indicate that Ca2+-activated centrin isoforms assemble into protein complexes with the visual heterotrimeric G-protein transducin. This interaction of centrins with transducin is mediated by binding to the betagamma-dimer of the heterotrimeric G-protein. More recent findings show that these interactions of centrins with transducin are reciprocally regulated via site-specific phosphorylations mediated by the protein kinase CK2. The assembly of centrin/G-protein complexes is a novel aspect of translocation regulation of signalling proteins in sensory cells, and represents a potential link between molecular trafficking and signal transduction in general.

中文翻译：

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视网膜感光细胞中的中心蛋白：连接纤毛中的调节剂。

细胞内Ca2 +浓度的变化直接或通常通过Ca2 +结合蛋白间接调节视觉信号转导级联。在这里，我们集中于中心蛋白，它们是脊椎动物视网膜感光细胞中Ca2 +结合蛋白的EF手超家族的高度保守亚组的成员。中心蛋白通常与中心体相关结构相关。在哺乳动物的视网膜感光细胞中，在连接纤毛的四个纤毛蛋白亚型被表达为连接纤毛的重要组分，纤毛将光敏的外段隔室与代谢活性的内段隔室相连。我们的数据表明，Ca2 +激活的着丝蛋白同工型与视觉异三聚体G蛋白转导蛋白组装成蛋白复合物。中心蛋白与转导蛋白的这种相互作用是通过与异源三聚体G蛋白的betagamma-二聚体结合而介导的。最近的研究结果表明，通过蛋白激酶CK2介导的位点特异性磷酸化作用，来调节蛋白与转导蛋白的这些相互作用。蛋白质/ G蛋白复合物的组装是感觉细胞中信号蛋白转运调节的一个新方面，通常代表分子运输和信号转导之间的潜在联系。