TRANSCRIPTIONAL CONTROL OF VACUOLAR H+-ATPASE EXPRESSION

质膜液泡H+ ATP酶（V-ATP酶）在细胞膜上具有重要的作用， 在肾碳酸氢盐转运、破骨细胞骨吸收和 巨噬细胞pH稳态。这些运输商占三分之一， 近端小管重吸收的重碳酸盐，和大多数的H+ 在集合管中运输，在那里精细控制酸分泌 发生。破骨细胞皱褶膜上的V-ATP酶是关键 创造骨骼生长所需的酸性微环境 吸收，并在巨噬细胞质膜上是必不可少的， 在酸性环境中的细胞内pH调节， 组织. 液泡H+ ATP酶在液泡系统中以低密度存在 所有的真核细胞。在专门的质子分泌细胞中， 近曲小管细胞、闰细胞、破骨细胞和巨噬细胞， 液泡H+ ATP酶的表达大大增强，高酶 质膜上的密度赋予细胞质子的能力 分泌物 这项建议的目的是确定负责以下方面的机制： 在特定细胞类型中扩增H+ ATP酶表达， 控制液泡H+-ATPase亚基的转录。具体 目的是：1a）分离和表征一个潜在的新的 一种调节液泡H+-ATP酶表达的转录因子， 单核细胞谱系的细胞; 1b）确定组织 该因子的分布和表达模式; 2）定义顺式- 液泡H ~+-ATP酶高水平所需的作用元件 在肾脏近端小管中的表达;以及3）验证 液泡H ~+-ATP酶启动子元件的作用 转基因小鼠模型。 这些研究将有助于理解基因调控元件 是特殊质子的终端分化所必需的， 运输细胞。所获得的信息还可能提供新的 对骨疾病中破骨细胞功能异常机制的认识， 免疫缺陷病症中的巨噬细胞功能障碍， 肾脏疾病中常见的尿液酸化。

Plasma membrane vacuolar H+ATPases (V-ATPases) have an essential role in renal bicarbonate transport, osteoclast bone resorption, and macrophage pH homeostasis. These transporters account for one third of proximal tubule bicarbonate reabsorption, and for the majority of H+ transport in the collecting duct, where fine control of acid secretion occurs. V-ATPases on the ruffled membranes of osteoclasts are crucial for creation of the acidic microenvironments required for bone resorption, and on macrophage plasma membranes are essential for intracellular pH regulation in acidic environments such as abscessed tissue. Vacuolar H+ATPases are present at low densities in the vacuolar system of all eukaryotic cells. In specialized proton-secreting cells such as the proximal tubule cell, intercalated cell, osteoclast and macrophage, vacuolar H+ATPase expression is greatly amplified, and the high enzyme density on the plasma membrane confers the capacity for cellular proton secretion. The goal of this proposal is to identify mechanisms responsible for amplified H+ATPase expression in specific cell types by analyzing the control of the vacuolar H+-ATPase subunit transcription. The specific aims are: 1a) to isolate and characterize a potentially novel transcription factor that regulates vacuolar H+-ATPase expression in cells of the monocytic lineage; 1b) to determine the tissue distribution and expression patterns of this factor; 2) to define cis- acting elements required for high levels of vacuolar H+-ATPase expression in the proximal tubule of the kidney; and 3) to verify the role of vacuolar H+-ATPase promoter elements through construction of a transgenic mouse model. These studies will aid in understanding the genetic regulatory elements that are required for terminal differentiation of specialized proton- transporting cells. The information obtained may also provide new insights on mechanisms of abnormal osteoclast function in bone disease, macrophage malfunction in immunodeficiency disorders, and the disorders of urinary acidification common in renal disease.