Ion Channel Transporter Interactions

摘要 阿尔茨海默病（AD）是一种神经退行性疾病，在我们的老龄化人群中越来越普遍 世界各地AD的特征是含有淀粉样β肽（Aβ）的斑块的积累， 神经系统紊乱以及认知缺陷恶化有力的证据表明硫胺素 AD患者体内平衡也可能发生改变。二磷酸硫胺素（TDP）水平降低， 糖代谢中依赖TDP的关键酶的功能发生在AD患者的血液和脑中。 硫胺素缺乏可加重斑块形成并改变淀粉样前体蛋白的代谢 在AD小鼠模型中，许多硫胺素依赖性过程减少， AD患者的大脑。我们先前发现了电压门控钾（Kv）通道的物理相互作用 与各种溶质转运蛋白结合。我们和其他研究小组已经报道了多种KV通道转运蛋白， 在体外和体内的相互作用，但其在AD中的潜在作用尚未确定， 报道了Kv通道与硫胺素转运蛋白的复合物。我们相信千伏通道传输器 复合体形成关键的信号枢纽，促进对高度动态的细胞过程的严格控制，并且 正如我们和其他人所表明的，它们的破坏与神经系统疾病有关，可能与AD有关。 在这里，建立在最近的初步数据表明神经元KCNQ通道之间的相互作用， 我们的目的是测试假设，KCNQ和/或KCNA Kv通道形成硫胺素转运蛋白， 与人硫胺素转运蛋白THTR-1和/或THTR-2的调节复合物，其是高亲和力的 通过质子梯度下降在细胞中浓缩硫胺素的转运蛋白。我们最近证明， AD患者的脑以及5XFAD（AD模型）小鼠的脑表达水平显著降低， THTR-1 -建立在先前的工作，表明硫胺素稳态改变AD， 缺乏会加重AD病理。此外，我们还发现，各种Kv通道，包括KCNQ 2/3， 形成复合物并与APP早期裂解产物C99共定位于郎维叶结，改变通道 在KCNQ 2/3的情况下，引起通道抑制。鉴于这些联系，我们假设朝中社 和KCNQ通道可以与硫胺素转运蛋白THTR-1和/或THTR-2形成物理复合物， 调节彼此的功能，我们将研究它们在AD中的变化。在两个具体目标中，我们将首先 研究通道-转运蛋白复合物形成在体外的存在和功能后果， KCNA、KCNQ Kv通道α亚基和硫胺素转运蛋白THTR-1和/或THTR-2。接下来，我们将调查 神经元KCNA和KCNQ通道亚型表达及其复合物形成的可能变化 在AD患者和小鼠脑的不同区域中具有硫胺素转运蛋白THTR-1和/或THTR-2 疾病的模型。在这个项目结束时，我们将建立新的通道转运蛋白 复合物，并确定它们是否被改变或有可能在AD的发病机制中发挥作用。

ABSTRACT Alzheimer’s disease (AD) is a neurodegenerative disorder that is increasingly prevalent in our aging populations around the world. AD is characterized by the accumulation of Amyloid-β peptide (Aβ)-containing plaques, neurofibrillary tangles, and also worsening cognitive deficits. Compelling evidence suggests that thiamine homeostasis may also be changed in AD. Reduction in thiamine diphosphate (TDP) levels and abnormal functioning of TDP-dependent key enzymes in glucose metabolism occur in the blood and brains of AD patients. Thiamine deficiency exacerbates plaque formation and alters the metabolism of Amyloid Precursor Protein Processing (APP) and/or Aβ in mouse models of AD; many thiamine-dependent processes are diminished in the brains of AD patients. We previously discovered physical interaction of voltage-gated potassium (Kv) channels with various solute transporters. We and other groups have since reported a variety of Kv channel-transporter interactions, both in vitro and in vivo, but their potential role in AD has not been established, neither have complexes of Kv channels with thiamine transporters been reported. We believe that Kv channel-transporter complexes form crucial signaling hubs facilitating tight control over highly dynamic cellular processes, and that their disruption, as we and others have shown, is associated with neurological diseases, and potentially AD. Here, building on recent preliminary data suggestive of interactions between neuronal KCNQ channels and thiamine transporters, we aim to test the hypothesis that KCNQ and/or KCNA Kv channels form reciprocally regulating complexes with the human thiamine transporters THTR-1 and/or THTR-2, which are high-affinity transporters that concentrate thiamine in cells via a downhill proton gradient. We recently demonstrated that brains of AD patients as well as those of 5XFAD (AD model) mice express significantly reduced levels of THTR-1 – building on prior work that demonstrated that thiamine homeostasis is altered in AD, and thiamine deficiency exacerbates AD pathology. In addition, we also found that various Kv channels, including KCNQ2/3, form complexes and co-localize in nodes of Ranvier with the APP early cleavage product C99, altering channel function and in the case of KCNQ2/3 causing channel inhibition. Given these links, we hypothesize that KCNA and KCNQ channels can form physical complexes with thiamine transporters THTR-1 and/or THTR-2 and thus regulate one another’s function, and we will study how they change in AD. In two Specific Aims we will first investigate in vitro existence and functional consequences of channel-transporter complex formation between KCNA, KCNQ Kv channel α subunits and thiamine transporters THTR-1 and/or THTR-2. Next, we will investigate possible changes in expression of neuronal KCNA and KCNQ channel isoforms, and their complex formation with thiamine transporters THTR-1 and/or THTR-2 in different regions of the brains of AD patients and a mouse model of the disease. At the conclusion of this project, we will have established novel channel-transporter complexes and determined whether they are altered or have the potential for a role in the pathogenesis of AD.