Coordinated SLC12A3/SLC12A6/SL26A4 electroneutral transport pathways maintain K+ homeostasis and acid-base balance

碱性饮食和碱性血症对钾的动态平衡有深远的影响，但潜在的 机制仍然知之甚少。在这里，我们提出一项创新计划，以结束这一意义重大的 知识鸿沟，建立在我们最近发现的长期追求的电子中和钾运输的基础上 路径。我们的数据显示，饮食中的碱负荷刺激了电子中性钾的表达 共转运蛋白KCC3a(SLc12a6)，与氯/HCO3-交换蛋白(SLC26A4)平行，在B- 类型插层细胞顶膜与噻嗪敏感的氯化钠的激活 (Slc12a3)，位于远端曲管。在这里我们提出了一个重要的假设，即KCC3a是 长期追捧的电子中和钾分泌途径并提出偶联的新思想 KCC3a、Pendrin和NCC之间维持钾和酸碱平衡，以响应 食用碱性和富含钾的食物，但会在碱性中毒中导致钾的浪费。这是一项新的 模型将由多学科专家团队进行严格测试，结合最先进的蜂窝 新的基因工程小鼠模型的生物学和生理表型。目标1将测试 假设KCC3a被激活，以响应碱性饮食的消耗和碱中毒来驱动 尿钾排泄。插层细胞特异性KCC3基因敲除小鼠将被调查以进行)测试 KCC3对钾平衡的贡献；b)对侧耳素介导的HCO3-分泌的贡献；c)阐明 KCC3表达调控的分子机制；c)检测KCC特异性 抑制剂可防止碱性血症中钾的流失。目标2将检验这样的假设，即吊坠蛋白与 KCC3a促进KHCO3分泌。将对吊环蛋白基因敲除小鼠进行研究，以确定：a) 吊环蛋白对KCC3a调节的贡献；以及b)解偶联的生理后果 传送者。我们还将探索KCC3a是否通过垂蛋白转录的变化来调节垂蛋白 涉及细胞内氯化物的变化。目标3将检验碱中毒导致WNK-SPAK的假设 NCC介导的磷酸化以确保电子中和碳酸氢钾分泌占优势 过度放电性钾分泌。新发现的DCT特异性Spak小鼠和In小鼠的得失 将对体外细胞模型进行测试，以严格测试这一想法并探索其机制。总而言之，这是 研究计划应该阐明一种新的机制来解释钾和酸碱平衡是如何 通过食用碱性和富含钾的食物而保存的，旧石器时代和 素食饮食。这项调查还有望改变教科书上对尿液的解释 碱中毒中钾的消耗，开辟了治疗的新天地。

Alkaline diets and alkalemia have a profound impact on potassium homeostasis, but the underlying mechanisms remain poorly understood. Here we propose an innovative plan to close this significant knowledge gap, building on our recent discovery of a long sought-after electroneutral potassium transport pathway. Our data reveal that dietary alkaline loading stimulates the expression of the electroneutral KCl cotransporter, KCC3a (Slc12a6), in parallel with the Cl-/HCO3- exchanger, pendrin (Slc26a4), on the B- type intercalated cell apical membrane and the activation of the thiazide-sensitive sodium-chloride, NCC (Slc12a3), in the Distal Convoluted Tubule. Here we advance the overarching hypothesis that KCC3a is the long sought-after electroneutral potassium secretory pathway and propose the novel idea that coupling between KCC3a, pendrin, and NCC maintains potassium and acid-base balance in response to the consumption of alkaline and potassium-rich foods but drives potassium wasting in alkalosis. This new model will be rigorously tested by a multidisciplinary team of experts, combining state-of-the-art cellular biology and physiological phenotyping in novel genetically engineered mouse models. Aim 1 will test the hypothesis that KCC3a is activated in response to the consumption of alkaline diets and alkalosis to drive urinary potassium excretion. Intercalated-cell-specific KCC3 knockout mice will be investigated to a) test the contribution of KCC3 to potassium balance and b) to pendrin-mediated HCO3- secretion; c) elucidate the molecular mechanisms that underlie the regulation of KCC3 expression; c) test if KCC-specific inhibitors prevent the loss of K+ in alkalemia. Aim 2 will test the hypothesis that pendrin is co-activated with KCC3a to increase KHCO3 secretion. Pendrin knockout mice will be studied to determine: a) the contribution of pendrin to the regulation of KCC3a; and b) the physiologic consequences of uncoupling the transporters. We will also explore if KCC3a regulates pendrin through changes in pendrin transcription that involve changes in intracellular chloride. Aim 3 will test the hypothesis that alkalosis drives WNK-SPAK mediated phospho-activation of NCC to ensure electroneutral potassium bicarbonate secretion prevails over electrogenic potassium secretion. Newly developed DCT-specific loss and gain of SPAK mice and in vitro cell models will be examined to rigorously test this idea and explore the mechanism. In summary, this program of investigation should illuminate a new mechanism to explain how K+ and acid-base balance are preserved with the consumption of alkaline and potassium-rich foods, typical of the paleolithic and vegetarian diets. The investigation is also expected to change the textbook explanation of urinary potassium wasting in alkalosis, opening a new therapeutic horizon.