Analysis of abnormal chloride transport in the pathogenesis of renal electrolyte disorders

1)假性醛固酮缺乏症II型(PHAII)是一种常染色体显性遗传病，以高钾血症、酸中毒和高血压为特征。对PHAII等单基因高血压疾病的研究将有助于深入了解血压调节的机制。我们通过建立一种理想的PHAII小鼠模型Wnk4^&lt；561a&gt；wnk4^&lt；561a；gt；来阐明PHAII的发病机制。我们清楚地表明PHAII的主要发病机制是激活WNK4-OSR1/SPAK-氯化钠共转运体(NCC)的磷酸化级联反应。2)CIC-K氯离子通道属于CLC氯离子通道家族，在肾脏跨上皮氯离子转运中起重要作用。为了发挥作用，CIC-K通道需要在合成后被转移到质膜上：这种转移需要与其b亚基Barttin结合。尽管CLC的晶体结构已被解析，但Barttin与CIC-K通道之间的结合作用尚未得到表征。在本研究中，我们试图通过免疫共沉淀和免疫荧光显微镜，利用不同的CIC-K2突变体来阐明Barttin在CIC-K2中的结合部位。我们发现Barttin能够与构成CIC-K2外侧面的结构域结合。这些关于结合位点的信息将有助于设计一类新的利尿剂或降压药来抑制CIC-K和Barttin的相互作用。

1) Pseudohypoaldosteronism type II (PHAII) is an autosomal-dominant disorder characterized by hyperkalemia, acidosis, and hypertension. Studies of monogenetic hypertensive diseases such as PHAII will provide insight into the mechanisms underlying blood pressure regulation. We clarified the pathogenesis of PHAII by generating Wnk4^<561A> knockin mice, an ideal mouse model of PHAII. We clearly showed that the major pathogenesis of PHAII is the activation of the phosphorylation cascade of the WNK4-OSR1/SPAK-NaCl cotransporter (NCC).2) CIC-K chloride channels belong to the CLC chloride channel family and play an important role in transepithelial chloride transport in the kidney. To be functional, CIC-K channels need to be translocated to the plasma membranes after synthesis : the translocation requires the binding to its b-subunit, barttin. The binding interaction between barttin and CIC-K channels has not been characterized, although the crystal structure of CLC was resolved. In the present study, we sought to clarify the binding sites of barttin in CIC-K2 by co-immunoprecipitation and immunofluorescence microscopy using various CIC-K2 mutants. We found that barttin was able to bind to the domains that constitute the outer lateral surfaces of CIC-K2. This information regarding the binding sites will be useful for designing a new class of diuretics or anti-hypertensive agents that inhibit the interaction of CIC-K and barttin.