Sodium Chloride Cotransporter Regulation by WNK Kinase

描述(由申请人提供)： WNKS(不含赖氨酸(K))是一个新发现的丝氨酸/苏氨酸激酶亚家族，参与控制上皮细胞的离子通透性。WNK1和WNK4激酶的突变被发现会导致假性低醛固酮增多症II型(PHA II)，也被称为Gordon综合征。PHA II是一种罕见的常染色体显性遗传病，以高血压、高钾血症和代谢性酸中毒为特征。其临床特征可被一种硫氮化物利尿剂逆转，该利尿剂是一种氯化钠共转运体(NCC)抑制剂。免疫荧光研究和Northern印迹分析表明，WNK1和WNK4都存在于参与氯离子转运的各种极化上皮细胞中，如肾脏、克隆窝、汗管、胰管、胆管、附睾部和脑室管膜。导致PHA II的WNK激酶突变表明，WNK激酶参与了远端肾单位对氯化钠的调节。最近的研究表明，WNK4对非洲爪哇卵母细胞的NCC活性和表面表达具有抑制作用，进一步证明WNK4通过直接或间接机制调节NCC的功能。本研究旨在探讨WNK4在肾小管上皮细胞NCC调控中的作用。需要检验的假设是，WNK4激酶的不适当靶向和/或功能将通过改变NCC的加工和/或间接改变NCC在哺乳动物细胞中的磷酸化来影响NCC的调节。这一假说得到了强大的初步数据的支持，即WNK4显著降低了NCC的表面表达。相反，在非洲绿猴肾(Cos-7)细胞中，NCC表面的表达不受WNK4突变体的影响。进一步研究WNK4对NCC的调节将为理解WNK4的生理作用提供重要信息，并有助于确定PHA II的潜在机制，这对于更好地理解高血压的发病机制是至关重要的。

DESCRIPTION (provided by applicant): WNKs (with no lysine (K)) are a newly described novel subfamily of serine/threonine kinases implicated in controlling the ionic permeability of epithelia. Mutations in WNK1 and WNK4 kinases are found to cause pseudohypoaldosteronism type II (PHA II), also referred to as Gordon syndrome. PHA II is a rare autosomal dominant disorder featuring hypertension, hyperkalemia and metabolic acidosis. Its clinical features are reversed by a thiazide diuretic, a sodium chloride cotransporter (NCC) inhibitor. Immunofluorescent studies and Northern blot analysis demonstrated that both WNK1 and WNK4 are present in a variety of polarized epithelia involved in chloride ion transport, such as kidney, clonic crypts, sweat ducts, pancreatic ducts, biliary ducts, epididymis and the ependyma of the brain. Mutations in WNK kinases resulting in PHA II suggest that WNK kinase is involved in the regulation of sodium chloride handling by the distal nephron. Recent studies have shown an inhibitory effect of WNK4 on NCC activity and surface expression of NCC in Xenopus oocytes, further demonstrating that WNK4 kinase regulates NCC function through direct or indirect mechanisms. This research proposal is to examine the role of WNK4 kinase in NCC regulation in the renal tubular cells. The hypothesis to be tested is that inappropriate targeting and/or function of the WNK4 kinase will affect NCC regulation directly by altering the NCC processing and/or indirectly by altering the phosphorylation of NCC in mammalian cells. This hypothesis is supported by strong preliminary data that surface expression of NCC is significantly reduced by WNK4. In contrast, NCC surface expression is unaffected by WNK4 mutants in African green monkey kidney (Cos-7) cells. Further investigating the regulation of NCC by WNK4 will provide important information to understanding the physiological role of WNK4 kinase and help to identify the underlying mechanisms of PHA II that are crucial in better understanding the pathogenesis of essential hypertension.