Molecular mechanisms for expression of renal potassium channels in doubly-perfused cultured collecting duct cells.

肾脏K的分泌是由集合管细胞介导的，而心尖ROMK K通道负责这种分泌。尽管许多研究人员已经研究了ROMK K通道活性的调节，但通道表达到根尖膜的确切机制仍不清楚。在本研究中，我们研究了外源转基因克隆的ROMK K通道在培养的M-1肾细胞中的表达机制。用荧光显微镜观察通道表达，用膜片钳技术检测通道电流。结果表明，ROMK在顶膜上的表达不需要膜上的PDZ结构域，而其他膜上表达ROMK通道需要PDZ结构域。由于ROMK K通道在体内仅表达于顶膜，而不表达于基底膜，提示ROMK K通道选择性地表达于膜可能不含ROMK-PDZ结构域的上皮细胞中。

Renal K secretion is mediated by the collecting duct cell, and apical ROMK K channels are responsible for this secretion. Although regulation of the ROMK K channel activity has been examined by many reserachers, precise mechanisms for channel expression to the apical membrane is still unknown. In this study, we investigated the expresssion mechanisms using exogeneously transfected cloned ROMK K channels to cultured M-1 kidney cells. Channel expression was observed with fluorescent microscope and channel current was examined using the patch-clamp technique. As the results, expression of ROMK to the apical membrane requred no PDZ domain in the membrane, but other membanes required PDZ domain to express ROMK K channels. Since ROMK K channels are expressed only to the apical membrane but not the basolateral membrane in vivo, it is suggested that ROMK K channels are selectively expressed to the apical membrane in the epithelial cells which may possesses no ROMK-PDZ domain in the membrane.