Trojan Philipp, Krauss Norbert, Choe Hui-Woog, Giessl Andreas, Pulvermüller Alexander, Wolfrum Uwe
Institut für Zoologie, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
Prog Retin Eye Res. 2008 May;27(3):237-59. doi: 10.1016/j.preteyeres.2008.01.003. Epub 2008 Jan 31.
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.
细胞内钙离子浓度的变化直接或更常见地通过钙结合蛋白间接调节视觉信号转导级联反应。在这里，我们聚焦于中心蛋白，它们是脊椎动物视网膜光感受器细胞中钙结合蛋白EF手超家族高度保守亚组的成员。中心蛋白通常与中心体相关结构有关。在哺乳动物视网膜光感受器细胞中，四种中心蛋白异构体作为连接光敏感外段区室与代谢活跃内段区室的连接纤毛中的主要成分表达。我们的数据表明，钙激活的中心蛋白异构体与视觉异源三聚体G蛋白转导素组装成蛋白复合物。中心蛋白与转导素的这种相互作用是通过与异源三聚体G蛋白的βγ二聚体结合介导的。最近的研究结果表明，中心蛋白与转导素的这些相互作用通过蛋白激酶CK2介导的位点特异性磷酸化相互调节。中心蛋白/G蛋白复合物的组装是感觉细胞中信号蛋白转位调节的一个新方面，总体上代表了分子运输与信号转导之间的潜在联系。
