CLCA protein and chloride transport in canine retinal pigment epithelium
CLCA protein and chloride transport in canine retinal pigment epithelium
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DOI：
10.1152/ajpcell.00210.2003
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发表时间：
2003-11-01
影响因子：
5.5
通讯作者：
Forsyth, GW
中科院分区：
文献类型：
--
作者：
Loewen, ME;Smith, NK;Forsyth, GW
穿过视网膜色素上皮 (RPE) 的离子和液体传输问题可能是视网膜感光细胞和 RPE 之间液体不适当积聚的原因。比较了参与基础液体跨 RPE 转运的 Cl-转运蛋白的活性，以确定 Ca2+- 或 cAMP 依赖性通道是否可能负责该组织中分泌活性的基础管家水平。候选 Ca2+ 依赖性 CLCA 蛋白在 Cl- 基础 RPE 转运中的作用已被研究。低浓度的Cl-电导抑制剂格列本脲和5-硝基-2-(3-苯基丙氨基)苯甲酸酯降低了安装在Ussing室中的狗RPE制剂中的短路电流，并减少了表达pCLCA1 Cl-电导调节剂的成纤维细胞的Ca2+依赖性Cl-流出。然而，这些相同的药物并没有抑制表达囊性纤维化跨膜调节器（CFTR）传导Cl-通道的培养成纤维细胞的Cl-释放速率。在犬 RPE 细胞的原代培养物或表达 pCLCA1 通道调节剂的成纤维细胞中添加离子霉素可增加两种类型培养细胞释放 Cl- 的速率。然而，pCLCA1的存在也增加了表达CFTR的成纤维细胞的cAMP依赖性Cl-释放。我们得出的结论是，对于通过 RPE 的正常液体分泌，Ca2+ 依赖性 Cl- 转运可能比 cAMP 依赖性 Cl- 转运更重要。此外，RPE 中表达的 CLCA 蛋白似乎调节其他 Cl-转运蛋白的活性，而不是充当主要离子转运蛋白。
Problems in ion and fluid transfer across the retinal pigment epithelium (RPE) are a probable cause of inappropriate accumulations of fluid between the photoreceptors of the retina and the RPE. The activities of Cl- transporters involved in basal fluid transfer across the RPE have been compared to determine whether Ca2+- or cAMP-dependent channels may be responsible for basal housekeeping levels of secretory activity in this tissue. The role of a candidate Ca2+-dependent CLCA protein in the basal RPE transport of Cl- has been investigated. Low concentrations of the Cl- conductance inhibitors glibenclamide and 5-nitro-2-(3-phenylpropylamino) benzoate reduced the short-circuit current in dog RPE preparations mounted in Ussing chambers and decreased the Ca2+-dependent Cl- efflux from fibroblasts expressing the pCLCA1 Cl- conductance regulator. However, these same agents did not inhibit the rate of Cl- release from cultured fibroblasts expressing the cystic fibrosis transmembrane regulator (CFTR) conductive Cl- channel. Addition of ionomycin to primary cultures of canine RPE cells or to fibroblasts expressing the pCLCA1 channel regulator increased the rate of release of Cl- from both types of cultured cells. However, the presence of pCLCA1 also increased cAMP-dependent Cl- release from fibroblasts expressing CFTR. We conclude that Ca2+-dependent Cl- transport may be more important than cAMP-dependent Cl- transport for normal fluid secretion across the RPE. Furthermore, CLCA proteins expressed in the RPE appear to regulate the activity of other Cl- transporters, rather than functioning as primary ion transport proteins.