Retinal Degeneration and Chloride Channels

 说明书(由申请人提供)：钙激活的氯离子通道(CaCC)是通过胞内钙离子的增加而打开的离子通道，并选择性地引导氯离子和其他阴离子沿其电化学梯度下降。它们最广为人知的功能是分泌上皮液。CaCC由两个不同基因家族的成员编码，Bestrophins和AnocTamins(也称为TMEM16)。BEST1的突变会导致一系列称为Bestrophinopsis的视网膜退行性变。ANO1和ANO2虽然还没有直接与视网膜疾病联系在一起，但在视网膜的各种细胞中都有表达，包括光感受器和RPE。自2008年发现ANO1以来，人们越来越明显地发现，ANO1具有惊人的多功能性：ANO1具有非常广泛的功能，包括感觉转导和适应、调节肌上皮细胞和平滑肌张力、控制神经元和心脏的兴奋性，以及伤害性感受。此外，越来越多的证据表明，ANO1在细胞生物学过程中发挥着重要作用，如调节细胞运动、增殖和原发纤毛发生。最近，我们观察到，当ANO1在非融合细胞中扩散到细胞表面时，随着细胞融合和极化，ANO1集中在一个独特的顶环(“Nimbus”)中。纤毛成为初级纤毛从细胞中出现的地方。初级纤毛是一种非运动性的细胞“天线”，充满了感觉受体，在组织的形态发生和发育中起着关键作用，并与细胞的增殖和迁移密切相关。参与纤毛发生的各种基因的突变会产生一种不同的人类疾病，称为纤毛病，这些疾病经常以视网膜退化为特征。我们发现，ANO1功能或表达的中断对初级纤毛的发育有深远的影响。本研究的目的是阐明ANO1在初级纤毛的发生和功能中的作用。我们推测，ANO1在组织顶膜的一个亚区以使其能够发生纤毛的过程中起关键作用。我们设想ANO1在这种情况下可能通过两种机制发挥作用。(I)ANO1可以作为支架，在顶膜上组织和协调纤毛生成蛋白。我们的蛋白质组学数据支持这一机制，即ANO1与纤毛发生所必需的蛋白质相互作用，这些纤毛蛋白调节ANO1电流。(Ii)氯离子通过ANO1的转运可能在纤毛发生中起作用。ANO1通道阻滞剂干扰纤毛发生的数据以及细胞外液中的阴离子种类对纤毛发生有深刻影响的数据支持了这一观点。由于初级纤毛是光感受器和视网膜色素上皮细胞的基本属性，了解ANO1在初级纤毛发生中的作用对视网膜生物学和视网膜疾病的治疗具有重要意义。

 DESCRIPTION (provided by applicant): Ca2+-activated Cl- channels (CaCCs) are ion channels that are opened by increases in cytosolic Ca2+ and selectively conduct Cl- and other anions down their electrochemical gradient. Their best known function is epithelial fluid secretion. CaCCs are encoded by members of two different gene families, Bestrophins and Anoctamins (also called TMEM16). Mutations in BEST1 cause a spectrum of retinal degenerations called bestrophinopthies. ANO1 and ANO2, while not yet linked directly to retinal disease, are expressed in a variety of cells in the retina including photoreceptors and RPE. Since their discovery in 2008, it has since become increasingly apparent that anoctamins are amazingly versatile: ANO1 has a very broad range of functions that encompass sensory transduction and adaptation, regulation of myoepithelial cell and smooth muscle tone, control of neuronal and cardiac excitability, and nociception. In addition, evidence is accumulating that ANO1 plays fundamental roles in cell biological processes like regulation of cell motility, proliferation, and primary ciliogenesis. Recently, we observed that ANO1, while spread over the cell surface in non-confluent cells, becomes concentrated in a distinctive apical torus (the "nimbus") as cells become confluent and polarize. The nimbus becomes the site where the primary cilium emerges from the cell. The primary cilium, a non-motile cellular "antenna" that is packed with sensory receptors, plays a pivotal role in tissue morphogenesis and development and is closely linked to cell proliferation and migration. Mutations in various genes involved in ciliogenesis produce a diverse spectrum of human disorders called ciliopathies that are very frequently characterized by retinal degeneration. We have found that disrupting ANO1 function or expression has profound effects on the development of the primary cilium. The goal of this research is to elucidate the role of ANO1 in the genesis and function of the primary cilium. We hypothesize that ANO1 plays a key role in organizing a subdomain of the apical membrane to make it competent for ciliogenesis to occur. We imagine two mechanisms by which ANO1 may function in this context. (i) ANO1 may operate as a scaffold to organize and coordinate ciliogenic proteins at the apical membrane. This mechanism is supported by our proteomic data that ANO1 interacts with proteins essential for ciliogenesis and that these ciliary proteins regulate ANO1 currents. (ii) Alternatively, Cl- transport through ANO1 may play a role in ciliogenesis. This idea is supported by data that ANO1 channel blockers disrupt ciliogenesis and that the species of anion in the extracellular solution has profound effects on ciliogenesis. Because the primary cilium is a fundamental property of both photoreceptors and retinal pigment epithelial cells, understanding the role of ANO1 in primary ciliogenesis has important implications for retinal biology and therapy of retinal diseases.