Ion Pump Partners: Regulators of Sorting and Function

描述（由申请人提供）：Na、K和H、K- atp酶是离子泵p型家族的成员，在维持细胞稳态和上皮转运中起关键作用。Na， k - atp酶产生离子梯度，维持细胞渗透平衡和膜电位。这些梯度通过运输上皮细胞来驱动各种溶质的进出口，以对抗陡峭的浓度梯度。H， k - atp酶负责胃酸分泌，似乎也在肾钾重吸收中起作用。为了实现这些功能，这些泵必须被限制在极化上皮细胞的质膜的特定区域。Na， k - atp酶位于大多数极化上皮细胞的基底外侧表面。在胃的泌酸壁细胞中，H， k - atp酶储存在细胞内的囊泡室中，在促分泌剂刺激下与顶质膜融合。这些离子泵的活性受到一系列过程的严格控制，这些过程调节着它们的亚细胞运输和催化性能。为了获得适当的亚细胞分布并参与各自的调控途径，这两个泵可能与大量辅助蛋白相互作用。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，以调节其细胞生物学和功能特性。我们发现Na， k - atp酶与神经素II/嗜脊髓蛋白和抑制蛋白都有关联，这表明钠泵可能受到类似于控制G蛋白偶联受体信号传导的调节机制的影响。此外，Na、K和H、K- atp酶各自与跨膜相互作用蛋白的四聚体家族成员形成复合物，这些关联深刻地影响泵运输。在目前的提案中，我们将开展旨在1)确定神经素II/嗜脊髓蛋白和抑制素调节Na， KATPase功能的分子和细胞生物学机制，2)表征离子泵和四聚体之间相互作用的生理效应，以及3)检查相互作用蛋白在体内调节离子泵功能中的作用。这些研究将使我们能够定义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病理条件下控制泵功能的参与。

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.