NBCe1-mediated Regulation of HCO3- is a Novel Mechanism Underlying Metabolic Reprogramming and Cystogenesis

项目摘要/摘要 葡萄糖刺激的胰岛素分泌丧失(GSIS)是一种重要的病理生理事件 2型糖尿病(T2 DM)患者高血糖的发生。最近的证据表明， 糖尿病患者的GSIS与线粒体功能降低的代谢重编程有关；然而 这些观察结果背后的机制在很大程度上仍不清楚。单细胞转录组学研究近况 人类β细胞发现SLC4A4是在T2 DMβ细胞中高表达的为数不多的独特基因之一 在非糖尿病β细胞中被抑制。SLC4a4编码胰腺中Na-nHCO3-共转运蛋白NBCe1B和 在调节细胞内pH(Phi)方面起着关键作用。重要的是，NBCe1的激活增加了 与细胞内糖酵解增强和线粒体功能受损有关，提示它可能 导致GSIS丧失，继而发展为T2 DM。初步的论文研究支持这一点。 假设并证明抑制β-细胞中的NBCE1B活性可改善体外GSIS并增强 体内葡萄糖耐量。这些累积的观察结果使我们制定了博士论文的方向 总体目标是表征NBCE1B作为一种新的β-细胞代谢和调节因子的作用 2型糖尿病患者的功能障碍。因此，特定目标1(F99)将检验T2 DM患者β细胞功能障碍的假设 由NBCe1B激活的细胞碱化介导的代谢重编程驱动。vt.给出 NBCe1在维持全身pH动态平衡中的关键作用，F99是我唯一要阐明的位置 K00期肾脏酸碱平衡失调的新机制。 具体地说，NBCe1(NBCe1a)的A-异构体是HCO3-重吸收的关键机制。 肾脏。NBCe1a缺失与代谢性酸中毒和集合管内的皮质囊肿相关 (CD)。可溶性腺酰环化酶(SAC)被认为是CD中的HCO3感受器。以前的工作 NBCe1A介导的HCO3重吸收受损可激活SAC-cAMP/PKA介导的 发信号。有趣的是，CD内持续的cAMP/PKA激活也被证明是一个关键 多囊肾病(PKD)中的囊性发育和增殖的介体。因此，主要的 我提出的博士后研究方向的目的是描述《NBCe1A》作为一部小说的作用 通过激活SAC-cAMP/PKA信号通路调节囊变。因此，具体目标2 (K00)将检验一种假设，即受损的NBCe1A介导的HCO3重吸收激活了一种可溶性的腺苷 Cyclase-cAMP/PKA信号通路在集合管促进增殖和囊变的实验研究 对PKD的研究。F99和K00一起，将推动我实现我的长期目标，领导一个独立的 肾脏病研究计划。

PROJECT SUMMARY/ABSTRACT The loss of glucose-stimulated insulin secretion (GSIS) is a critical pathophysiological event precipitating development of hyperglycemia in Type 2 diabetes mellitus (T2DM). Recent evidence suggests that loss of GSIS in diabetes is associated with metabolic reprogramming toward reduced mitochondrial function; however mechanisms underlying these observations remain largely unknown. Recent single cell transcriptomics studies of human β-cells identified SLC4A4 as one of few unique genes highly expressed in T2DM β-cells and repressed in non-diabetic β-cells. Slc4a4 encodes for Na+-nHCO3- cotransporter, NBCe1B in the pancreas and plays a key role in regulating intracellular pH (pHi). Importantly, increased activation of NBCe1 has been associated with enhanced intracellular glycolysis and impaired mitochondrial function suggesting it may contribute to loss of GSIS and consequent development of T2DM. Preliminary dissertation studies support this hypothesis and demonstrate that inhibition of NBCe1B activity in β-cells improves GSIS in vitro and enhances glucose tolerance in vivo. These cumulative observations led us to develop a doctoral dissertation direction with an overall objective to characterize the role of NBCe1B as a novel regulator of β-cell metabolism and dysfunction in T2DM. Accordingly, Specific Aim 1 (F99) will test the hypothesis that β-cell dysfunction in T2DM is driven by metabolic reprogramming mediated by cellular alkalization through activation of NBCe1B. Given the critical role of NBCe1 in maintaining systemic pH homeostasis, the F99 uniquely positions me to elucidate novel mechanisms associated with dysregulation of acid-base balance in the kidney during the K00 phase. Specifically, the A-isoform of NBCe1 (NBCe1A) functions as the key mechanism of HCO3- reabsorption in the kidney. Deletion of NBCe1A is associated with metabolic acidosis and cortical cysts within the collecting duct (CD). Soluble adenylyl cyclase (sAC) has been identified as a HCO3- sensor within the CD. Previous work demonstrated that impaired NBCe1A-mediated HCO3- reabsorption activates sAC-cAMP/PKA mediated signaling. Interestingly, persistent cAMP/PKA activation within the CD has also been demonstrated to be a key mediator of cyst development and proliferation in polycystic kidney disease (PKD). Therefore, the main objective of my proposed postdoctoral research direction is to characterize the role of NBCe1A as a novel regulator of cystogenesis through activation of sAC-cAMP/PKA signaling pathway. Accordingly, Specific Aim 2 (K00) will test the hypothesis that impaired NBCe1A-mediated HCO3- reabsorption activates a soluble adenylyl cyclase-cAMP/PKA signaling cascade in the collecting duct promoting proliferation and cystogenesis in models of PKD. Together, the F99 and K00 will propel me to achieve my long-term goal to lead an independent research program in nephrology.