Regulation of Renal Phosphate Transport by Lipids

脂质对肾磷酸盐转运的调节

• 批准号: 7215593
• 负责人: MOSHE LEVI
• 金额: $ 30.46万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7215593
• 关键词: Acquired Immunodeficiency Syndrome; Actins; Acute; Affect; Age; Aging; Aging-Related Process; Alcoholism; Apical; Biochemical; Biological Assay; Brush Border; Cardiovascular Physiology; Cardiovascular system; Carrier Proteins; Cell Line; Cell physiology; Cells; Characteristics; Chemicals; Cholesterol; Clinical; Co-Immunoprecipitations; Cytoskeleton; Data; Diabetes Mellitus; Didelphidae; Dietary Factors; Diffusion; Disease; ERM protein; Endocytosis; Enzymes; Exocytosis; Family; Fluorescence; Fluorescence Microscopy; Fluorescence Recovery After Photobleaching; Fluorescence Resonance Energy Transfer; G(M3) Ganglioside; Glucocorticoids; Glucosylceramides; Glycosphingolipids; Homeostasis; Hormonal; Hormones; Human; Hypophosphatemia; Impairment; In Vitro; Kidney; Laboratories; Lateral; Lipids; Malignant Neoplasms; Measures; Mediating; Membrane; Membrane Lipids; Membrane Microdomains; Metabolic; Metabolism; Microscopy; Modification; Molecular; Molecular Conformation; Mus; Organ; Oryctolagus cuniculus; Pharmaceutical Preparations; Physiologic calcification; Physiological; Play; Post-Translational Regulation; Potassium; Potassium Deficiency; Proteins; Proximal Kidney Tubules; Rattus; Regulation; Role; Spectrum Analysis; Sphingomyelins; System; Techniques; Therapeutic; Transcriptional Regulation; Transplantation; Tubular formation; apical membrane; brush border membrane; crosslink; extracellular; ezrin; fluorescence imaging; inhibitor/antagonist; inorganic phosphate; inter-alpha-inhibitor; kidney cell; kidney cortex; lipid transport; protein expression; response; sodium-phosphate cotransporter proteins; trafficking

DESCRIPTION (provided by applicant): Disorders of extracellular inorganic phosphate (Pi) concentration and impairment in Pi reabsorption are common clinical problems. Aging, diabetes mellitus, malignancy, alcoholism, transplantation, AIDS, and several therapeutic drugs are well known to cause or to be associated with hypophosphatemia or hyperphosphatemia, mainly by affecting renal tubular Pi transport. Disorders of phosphate metabolism have severe consequences on organ function including the cardiovascular system and bone mineralization. The kidney plays a critical role in the regulation of Pi homeostasis. The evidence to date indicates that regulation of the overall renal tubular Pi transport by dietary, hormonal, or metabolic factors occurs at the level of the proximal tubular apical brush border membrane (BBM) Na/Pi cotransport system (NaPi-IIa protein). Studies in our laboratory have determined that alterations in renal lipid composition, including cholesterol and glycosphingolipids play an important role in the regulation of renal Na/Pi cotransport activity and BBM membrane microdomains (or lipid rafts). The mechanisms how lipids modulate Na/Pi transport activity and NaPi-Iia protein expression and trafficking however are not well known and need to be elucidated. Our hypotheses are that perturbations in membrane cholesterol and glycosphingolipid composition regulate Na/Pi transport activity by coordinated cellular and molecular mechanisms that include I) modulating the formation of cholesterol and glycosphingolipid enriched lipid microdomains or lipid rafts that results in increased dynamic partitioning of the Na/Pi cotransporter protein in the lipid microdomains, II) modulating the lateral diffusion or mobile fraction and/or the clustering or aggregation and/or the conformational change of the Na/Pi transport proteins at the level of the apical membrane, and lII) modulating the vesicular trafficking of the Na/Pi transport protein, including endocytosis from and/or exocytosis to the apical membrane in response to alterations in extracellular Pi or PTH. The specific aims of this proposal are: 1) To determine if alterations in cholesterol and/or glycosphingolipid composition modulate a) the dynamics of cholesterol and glycosphingolipid enriched membrane microdomains (lipid rafts), b) the partitioning of the Na/Pi cotransporter proteins in the cholesterol and glycosphingolipid enriched membrane microdomains, and e) the function or transport activity of Na/Pi cotransporter proteins in these domains; 2) To determine if alterations in cholesterol or glycosphingolipid composition modulates a) the lateral diffusion and mobility, or b) the clustering and aggregation, or e) the conformational state of Na/Pi protein molecules; 3) To determine if alterations in cholesterol or glycosphingolipid composition modulates a) the apical membrane expression of Na/Pi protein and b) the acute trafficking of Na/Pi protein in response to alterations in extracellular Pi or PTH and c) the role of the actin cytoskeleton in regulation of NaPi trafficking.

描述（由申请人提供）：细胞外无机磷酸盐（Pi）浓度紊乱和Pi重吸收受损是常见的临床问题。众所周知，衰老、糖尿病、恶性肿瘤、酗酒、移植、艾滋病和几种治疗药物主要通过影响肾小管Pi转运而引起或与低磷血症或高磷血症相关。磷酸盐代谢紊乱对心血管系统和骨矿化等器官功能产生严重影响。肾脏在调节 Pi 稳态中起着至关重要的作用。迄今为止的证据表明，饮食、激素或代谢因素对整个肾小管 Pi 转运的调节发生在近端肾小管顶端刷状缘膜 (BBM) Na/Pi 共转运系统（NaPi-IIa 蛋白）水平。我们实验室的研究已经确定，肾脂质成分（包括胆固醇和鞘糖脂）的改变在肾 Na/Pi 共转运活性和 BBM 膜微域（或脂筏）的调节中发挥重要作用。然而，脂质如何调节 Na/Pi 转运活性和 NaPi-Iia 蛋白表达和运输的机制尚不清楚，需要阐明。 我们的假设是，膜胆固醇和鞘糖脂组成的扰动通过协调的细胞和分子机制调节Na/Pi转运活性，包括I)调节胆固醇和鞘糖脂富集的脂质微域或脂筏的形成，从而导致Na/Pi的动态分配增加。脂质微结构域中的 Pi 协同转运蛋白，II) 调节脂质体的横向扩散或移动部分和/或聚类或聚集和/或构象变化顶膜水平的Na/Pi转运蛋白，以及lII)调节Na/Pi转运蛋白的囊泡运输，包括响应于细胞外Pi或PTH的改变而从顶膜进行内吞作用和/或向顶膜进行胞吐作用。 该提案的具体目标是：1) 确定胆固醇和/或鞘糖脂组成的变化是否调节 a) 胆固醇和鞘糖脂富集膜微域（脂筏）的动态，b) Na/Pi 协同转运蛋白在富含胆固醇和鞘糖脂的膜微结构域，以及 e) 这些结构域中 Na/Pi 协同转运蛋白的功能或转运活性； 2) 确定胆固醇或鞘糖脂组成的改变是否调节 a) 横向扩散和迁移，或 b) 聚类和聚集，或 e) Na/Pi 蛋白质分子的构象状态； 3) 确定胆固醇或鞘糖脂组成的变化是否调节 a) Na/Pi 蛋白的顶膜表达，b) Na/Pi 蛋白响应细胞外 Pi 或 PTH 变化的急性运输，以及 c)肌动蛋白细胞骨架调节 NaPi 运输。