Ion Pump Partners: Regulators of Sorting and Function

描述(申请人提供)：Na，K和H，K-ATPase是P型离子泵家族的成员，在维持细胞内稳态和跨上皮运输方面发挥关键作用。Na，K-ATPase产生维持细胞渗透平衡和膜电位的离子梯度。通过运输上皮细胞来利用这些梯度来驱动各种溶质的输入和输出，以对抗陡峭的浓度梯度。H，K-ATPase负责胃酸的分泌，似乎也在肾脏钾的重吸收中发挥作用。为了执行这些功能，这些泵必须被限制在极化上皮细胞质膜的特定区域。Na，K-ATPase存在于大多数极化上皮细胞的基底外侧表面。在胃酸分泌的壁细胞中，H，K-ATPase被储存在细胞内的囊泡室中，该囊泡室与顶端质膜融合，以响应促分泌剂的刺激。这些离子泵的活动通过各种过程受到严格控制，这些过程既调节了它们的亚细胞运输，也调节了它们的催化性能。为了获得合适的亚细胞分布并参与各自的调控途径，两个泵都可能与大量的辅助蛋白相互作用。在之前的资助期间，我们已经确定了几个新的伙伴多肽，它们似乎与这些泵相互作用，调节它们的细胞生物学和功能特性。我们发现Na，K-ATPase与Neurabin II/Spinophin和Arrestin都有关联，这表明钠泵可能对G蛋白偶联受体信号转导的调控机制敏感。此外，Na，K和H，K-ATPase都与跨膜相互作用蛋白Tetraspan家族的一个成员形成复合物，这些结合深刻地影响泵的运输。在目前的方案中，我们将开展旨在1)确定Neurabin II/Spinophin和Arrestin调节Na，KATPase功能的分子和细胞生物学机制，2)表征离子泵和Tetraspan之间相互作用的生理效应，以及3)研究相互作用的蛋白质在体内调节离子泵功能的作用。这些研究将使我们能够确定这些新的相互作用的生理意义，并了解它们在正常情况下和在病理条件下参与调节泵的功能。

DESCRIPTION (provided by applicant): The Na, K and H, K-ATPases are members of the P-type family of ion pumps and play critical roles in maintaining cellular homeostasis and transepithelial transport. The Na, K-ATPase creates ion gradients that maintain cellular osmotic balance and membrane potential. These gradients are exploited by transporting epithelia to drive the import and export of a wide range of solutes against steep concentration gradients. The H, K-ATPase is responsible for gastric acid secretion and also appears to play a role in renal potassium reabsorption. To carry out these functions, these pumps must be restricted to specific domains of the plasma membranes of polarized epithelial cells. The Na, K-ATPase resides at the basolateral surfaces of most polarized epithelial cell types. In the acid secreting parietal cells of the stomach the H, K-ATPase is stored in an intracellular vesicular compartment that fuses with apical plasma membrane in response to secretagogue stimulation. The activities of these ion pumps are tightly controlled through a variety of processes that regulate both their subcellular trafficking and their catalytic properties. In order to attain their appropriate subcellular distributions and to participate in their respective regulatory pathways, both pumps are likely to interact with a large number of accessory proteins. During the previous funding period we have identified a several novel partner polypeptides that appear to interact with these pumps to modulate their cell biologic and functional properties. We find that the Na,K-ATPase associates with both neurabin II/spinophilin and arrestin, suggesting that the sodium pump may be susceptible to regulatory mechanisms similar to those that govern G protein coupled receptor signaling. In addition, the Na, K and H, K-ATPase each form complexes with a member of the tetraspan family of transmembrane interacting proteins, and these associations profoundly influence pump trafficking. In the present proposal we will carry out studies designed to 1) determine the molecular and cell biologic mechanisms through which neurabin II/spinophilin and arrestin modulate the function of the Na, KATPase, 2) characterize the physiologic effects of interactions between ion pumps and tetraspans, and 3) examine the role of interacting proteins in governing ion pump function in vivo. These studies will allow us to define the physiological significance of these novel interactions, and to understand their involvement in governing pump function both under normal circumstances and in the context of pathological conditions.