Acid-Base and Ammonia Transport in the Collecting Duct

酸碱和氨在收集管中的传输

• 批准号: 8511335
• 负责人: L Lee HAMM
• 金额: --
• 依托单位: SOUTHEAST LOUISIANA VETERANS HEALTH CARE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8511335
• 关键词: Accounting; Acid-Base Equilibrium; Acids; Address; Ammonia; Ammonium; Bacteria; Bicarbonates; Biological Assay; Carbon Dioxide; Cellular Assay; Characteristics; Chronic; Chronic Kidney Failure; Data; Diabetes Mellitus; Diagnosis; Disease; Distal; Duct (organ) structure; Equilibrium; Erythroid; Excretory function; Gases; Glycoproteins; Goals; Health; Homeostasis; Human; Hypertension; In Vitro; Ions; Kidney; Liver; Measurement; Measures; Mediator of activation protein; Membrane Proteins; Microelectrodes; Modeling; Molecular; Mus; Nephrons; Physiological; Prevention; Process; Property; Proteins; Regulation; Renal function; Resolution; Role; Site-Directed Mutagenesis; Skin; Structure; Techniques; Testis; Up-Regulation; Urine; Veterans; Work; Yeasts; base; kidney cortex; novel; pH Homeostasis; protein transport; public health relevance; research study; solute; voltage; voltage clamp

DESCRIPTION (provided by applicant): Renal excretion of NH4+ is critical for acid-base homeostasis, normally accounting for at least two-thirds of daily net acid excretion in the urine. Recent studies have identified new non- erythroid Rh proteins that are related to the NH4+ transporters in non-mammalian species. Normal acid-base balance is essential for health and prevention of progression of chronic kidney disease. The main purpose of this proposal is to determine the functional and structural properties of renal Rh glycoproteins with respect to NH3/NH4+ transport and CO2 transport which is also critical for acid-base homeostasis. Among the properties to be explored are their critical sensitivity to pH; a potential role as transporters of gases and the possibility that they serve dual roles as NH4+ and NH3 transporters. Specifically we will address the following aims: 1) Transport characteristics of Rh glycoproteins: The main hypothesis of this aim is that Rhbg and Rhcg are transporters of NH4+ (and possibly NH3). 2) Structure-function characteristics of Rh glycoproteins: Site-directed mutagenesis of critical residues & functional assays will be conducted to determine why different Rh glycoproteins transport NH3/NH4+ differently. 3) Transport of NH3 and CO2 by Rh glycoproteins: We will determine if Rh proteins transport NH3 or CO2. This property is novel & unique in that very few membrane proteins have been identified as mediators of gas transport. Our studies employ a combination of techniques (pHi studies, voltage clamp experiments, site-directed mutagenesis) that should clearly establish whether Rh proteins act as NH3 or CO2 or NH4+ transporters and the characteristics of this transport. This work relies on in vitro experiments because of the difficulties inherent in characterizing NH3/NH4+ transport. The proposed work is substantial, but our ultimate goals are to understand the physiologic significance and regulation of these processes in the kidney.

描述（由申请人提供）： NH4+ 的肾脏排泄对于酸碱稳态至关重要，通常至少占尿液中每日净酸排泄量的三分之二。最近的研究发现了与非哺乳动物物种中的 NH4+ 转运蛋白相关的新非红细胞 Rh 蛋白。正常的酸碱平衡对于健康和预防慢性肾脏病的进展至关重要。 该提案的主要目的是确定肾 Rh 糖蛋白在 NH3/NH4+ 转运和 CO2 转运方面的功能和结构特性，这对于酸碱稳态也至关重要。待探索的特性包括它们对 pH 值的临界敏感性；作为气体运输者的潜在作用以及它们的可能性 具有 NH4+ 和 NH3 转运蛋白的双重作用。具体来说，我们将实现以下目标： 1）Rh 糖蛋白的转运特性：该目标的主要假设是 Rhbg 和 Rhcg 是 NH4+（也可能是 NH3）的转运蛋白。 2) Rh 糖蛋白的结构-功能特征：将进行关​​键残基的定点诱变和功能测定，以确定为什么不同的 Rh 糖蛋白以不同的方式转运 NH3/NH4+。 3) Rh 糖蛋白转运 NH3 和 CO2：我们将确定 Rh 蛋白是否转运 NH3 或 CO2。这种特性是新颖且独特的，因为很少有膜蛋白被确定为气体运输的介质。 我们的研究采用了多种技术（pHi 研究、电压钳实验、定点诱变）的组合，应明确确定 Rh 蛋白是否充当 NH3、CO2 或 NH4+ 转运蛋白以及这种转运的特征。由于表征 NH3/NH4+ 转运的固有困难，这项工作依赖于体外实验。拟议的工作是实质性的，但我们的最终目标是了解肾脏中这些过程的生理意义和调节。