Expression and comparative characterization of Gq-coupled invertebrate visual pigments and melanopsin
Expression and comparative characterization of Gq-coupled invertebrate visual pigments and melanopsin
复制标题
DOI：
10.1111/j.1471-4159.2007.05184.x
复制
发表时间：
2008-05-01
影响因子：
4.7
通讯作者：
Shichida, Yoshinori
中科院分区：
文献类型：
--
作者：
Terakita, Akihisa;Tsukamoto, Hisao;Shichida, Yoshinori
非视觉色素黑素定位于感光性视网膜神经节细胞，参与哺乳动物昼夜节律的光包裹和瞳孔反应，在系统发育上与昆虫、头足类等无脊椎动物的视觉色素相近。最近的研究表明，黑素是一种双稳态色素，像无脊椎动物的视觉色素一样，驱动Gq介导的信号转导级联。由于视觉细胞和感光神经节细胞的详细电生理特性有所不同，我们在此表达和纯化了无脊椎动物视觉色素和黑素蛋白，以比较研究它们对GQ的激活能力。我们成功地表达和纯化了蜜蜂的紫外光和蓝光敏感的视觉色素以及文昌鱼的黑色素。虽然纯化的紫外光敏感色素和黑素在纯化过程中失去了双稳性质，但色素在脂泡中的重组导致了双稳性质的恢复。这些重组色素的光依赖GQ激活能力相似，表明电生理差异不取决于GQ激活步骤，而取决于其他信号转导步骤和/或细胞属性。我们的发现也很重要，因为这是第一份报告描述了GQ偶联无脊椎动物视觉色素在培养细胞中的异源大规模表达。
A non-visual pigment melanopsin, which is localized in photosensitive retinal ganglion cells and is involved in the circadian photoentrainment and pupillary responses in mammals, is phylogenetically close to the visual pigments of invertebrates, such as insects and cephalopods. Recent studies suggested that melanopsin is a bistable pigment and drives a Gq-mediated signal transduction cascade, like the invertebrate visual pigments. Because detailed electrophysiological properties are somewhat different between the visual cells and the photosensitive ganglion cells, we here expressed and purified the invertebrate visual pigment and melanopsin to comparatively investigate their Gq-activation abilities. We successfully expressed and purified UV and blue light-sensitive visual pigments of the honeybee as well as the amphioxus melanopsin. Although the purified UV-sensitive pigment and the melanopsin lost their bistable nature during purification, reconstitution of the pigments in lipid vesicles resulted in return of the bistable nature. The light-dependent Gq-activation abilities among these reconstituted pigments are similar, suggesting that the electrophysiological differences do not depend on the Gq-activation step but rather on the other signal transduction steps and/or on cell properties. Our findings are also important in that this is the first report describes a heterologous large-scale expression of the Gq-coupled invertebrate visual pigments in cultured cells.