Genetic Control of Vacuolar H+-ATPase Expression

描述（由申请人提供）：液泡质子易位ATP酶，或v -ATP酶，是一种多亚基复合物，利用ATP水解产生的能量将质子输送到细胞膜上。在大多数真核生物中，v - atp酶仅存在于内吞网络的膜中，在那里它们用于酸化核内体、溶酶体、反式高尔基体和其他空泡室。然而，一些特化的细胞类型，包括肾上皮细胞、破骨细胞、巨噬细胞和神经元，在特化的亚细胞区室中高水平表达v - atp酶，在这些亚细胞区室中，v - atp酶对尿液酸化、骨吸收、调节细胞内pH值和调节神经递质的囊泡摄取等多种功能至关重要。V-ATPases在哺乳动物细胞中发挥的多种功能可归因于多种亚基亚型的表达、总体表达水平的差异以及调节靶向特定膜室的能力。人类v - atp酶的不适当表达已被证明可导致严重的疾病状态，包括肾小管酸中毒、耳聋和骨质疏松。

DESCRIPTION (provided by applicant): The vacuolar proton-translocating ATPase, or V-ATPase, is a multi-subunit complex that uses energy from ATP hydrolysis to transport protons across cellular membranes. In most eukaryotes, V-ATPases reside solely in membranes of the endocytic network, where they serve to acidify endosomes, lysosomes, the trans-Golgi, and other vacuolar compartments. However, some specialized cell types, including kidney epithelia, osteoclasts, macrophages, and neurons, express the V-ATPase at high levels and in specialized subcellular compartments, where the enzyme is critical for such diverse functions as urinary acidification, bone resorption, regulation of intracellular pH, and regulated vesicular uptake of neurotransmitters. The variety of functions performed by V-ATPases among mammalian cells is attributable to expression of multiple subunit isoforms, differences in overall expression levels, and the capacity for regulated targeting to specialized membrane compartments. Inappropriate expression of V-ATPase in humans has been shown to lead to serious disease states, including renal tubular acidosis, deafness, and osteopetrosis. The genetic controls that regulate V-ATPase expression must be varied and diverse to meet the specific proton-transport needs of many specialized cell types, as well as its constitutive role in the endocytic network. These include both transcriptional and post-transcriptonal mechansims, as well as intracellular targeting of both V-ATPase mRNA and proteins. The long-term goal of this project is to understand the mechanisms by which V-ATPases are expressed at appropriate levels and in appropriate membrane compartments. To this end, the specific aims are directed toward (1) examining mechanisms by which V-ATPase mRNA stability is regulated in proton-secreting cells such as macrophages and kidney epithelia; (2) examining determinants within V-ATPase mRNAs that mediate intracellular trafficking in specialized cell types; and (3) defining genetic elements that control expression of a uniquely regulated V-ATPase subunit involved in intracellular trafficking. These aims will be achieved through experiments in which V-ATPase mRNAs are genetically manipulated in cell culture models; the effects of these manipulations of V-ATPase expression and cell function will be determined.