Mechanisms and relevance of ENaC regulation by EGF and Rac1

EGF 和 Rac1 调节 ENaC 的机制和相关性

• 批准号: 8584320
• 负责人: ALEXANDER STARUSCHENKO
• 金额: $ 37.49万
• 依托单位: MEDICAL COLLEGE OF WISCONSIN
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-12-01 至 2016-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8584320
• 关键词: Address; Aldosterone; Binding; Biochemical; Blood Pressure; Blood Volume; Cardiovascular Diseases; Cardiovascular system; Cell membrane; Cells; Chronic; Coupling; Dahl Hypertensive Rats; Data; Development; Diet; Disease; Distal; Electrolytes; Ensure; Environment; Epidermal Growth Factor; Family; Family member; Fluid Balance; Functional disorder; Growth Factor; Homeostasis; Hypertension; In Vitro; Ion Channel; Kidney; Kidney Diseases; Laboratories; Lead; Ligands; Liquid substance; Lung; Mediating; Microscopy; Molecular; Monomeric GTP-Binding Proteins; Nephrons; Pathology; Pathway interactions; Physiological; Physiology; Play; Proteins; Protocols documentation; Publishing; Rat Strains; Rattus; Recycling; Regulation; Role; Signal Pathway; Signal Transduction; Sodium; Sodium Chloride; Specificity; Up-Regulation; WAVE protein; Wisconsin; Work; base; blood pressure regulation; design; epithelial Na+ channel; genetic regulatory protein; hemodynamics; in vivo; inhibitor/antagonist; insight; instrument; medical schools; member; overexpression; receptor; research study; response; rhoB p20 GDI; salt sensitive; salt sensitive hypertension; small hairpin RNA; trafficking

DESCRIPTION (provided by applicant): Long term control of blood pressure involves Na+ homeostasis through the precise regulation of the Epithelial Na+ Channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN). ENaC dysfunction is causative for disturbances in total body Na+ levels associated with abnormal regulation of blood volume, blood pressure, and lung fluid balance. We provide preliminary evidence that epidermal growth factor (EGF) can serve as an ENaC ligand and hypothesize that members of the EGF-family and Rac1 modulate ENaC-mediated Na+ transport in the ASDN and participate in the development of salt-sensitive hypertension. EGF and its related EGF-family members bind to ErbB receptors and act as signaling factors responsible for renal development, physiology and pathophysiology. Under physiological conditions, ErbB receptors play an important role in the regulation of renal hemodynamics and electrolyte handling by the kidney, while in different pathophysiological states ErbB activation may mediate either beneficial or detrimental effects on the kidney. Stimulation of ErbB receptors activates an intracellular cascade involving small GTPases, particularly Rac1. Small G proteins and their regulatory proteins contribute to the pathology of renal and cardiovascular diseases. Our preliminary results, including electrophysiological experiments using isolated, split open ASDN, demonstrate that ENaC is regulated by EGF and Rac1, possibly through a convergent mechanism. Dahl salt-sensitive (SS) rats used in these studies develop severe hypertension on high-salt diet. We provide preliminary data indicating that ENaC contributes to the development of hypertension in the SS rat strain. Furthermore, our preliminary data reveal that EGF concentration is reduced in the SS rats, which we propose would enhance ENaC activity, sodium retention and hypertension. Building upon this preliminary data and our previously published findings, the specific objective of this proposal is to determine whether EGF acting through Rac1 is important for physiologic control of renal sodium handling through regulation of ENaC and define the precise mechanisms of EGF- and Rac1-mediated changes in ENaC activity. A combination of electrophysiological, immunohistochemical, biochemical, microscopy and chronic studies in vivo and in vitro will be used in this proposal to provide mechanistic insights on how ENaC is regulated by member of the EGF-family and Rac1 and how changes in this pathway contributes to salt induced hypertension in SS rats. These studies will address three Specific Aims: 1) To identify and quantify the role of EGF and related growth factors in the physiological regulation of ENaC activity in the ASDN and establish the role of this pathway in the development of salt-sensitive hypertension; 2) To establish the physiological role of RhoGDI and Rac1 in regulation of ENaC and determine the role of Rac1 in mediating EGF effects on ENaC; and 3) To define the cellular and molecular mechanism by which Rac1 modulates ENaC activity: do WAVEs convey Rac1 regulation to ENaC?

描述（由申请人提供）：长期控制血压涉及通过精确调节醛固酮敏感远端肾元（ASDN）中上皮Na+通道（ENaC）的Na+稳态。ENaC功能障碍可引起与血容量、血压和肺液平衡异常调节相关的全身Na+水平紊乱。我们提供了表皮生长因子（EGF）可以作为ENaC配体的初步证据，并假设EGF家族成员和Rac1在ASDN中调节ENaC介导的Na+转运并参与盐敏感性高血压的发展。EGF及其相关EGF家族成员与ErbB受体结合，作为肾脏发育、生理和病理生理的信号因子。生理条件下，ErbB受体在肾脏血流动力学和电解质处理的调节中发挥重要作用，而在不同的病理生理状态下，ErbB的激活可能介导对肾脏的有益或有害的影响。ErbB受体的刺激会激活细胞内涉及小gtp酶的级联反应，尤其是Rac1。小G蛋白及其调控蛋白参与肾脏和心血管疾病的病理。我们的初步结果，包括使用分离的、劈开的ASDN进行的电生理实验，表明ENaC受EGF和Rac1的调控，可能是通过一种会聚机制。在这些研究中使用的达尔盐敏感（SS）大鼠在高盐饮食中发生严重的高血压。我们提供的初步数据表明，ENaC有助于SS大鼠品系高血压的发展。此外，我们的初步数据显示，EGF浓度在SS大鼠中降低，我们认为这可能会增强ENaC活性，钠潴留和高血压。基于这些初步数据和我们之前发表的研究结果，本提案的具体目标是确定EGF通过Rac1对ENaC的调节对肾钠处理的生理控制是否重要，并确定EGF和Rac1介导的ENaC活性变化的确切机制。本研究将结合电生理、免疫组织化学、生化、显微镜和体内和体外慢性研究，提供ENaC如何受egf家族成员和Rac1调节的机制见解，以及该途径的变化如何促进盐诱导的SS大鼠高血压。这些研究将解决三个具体目标：1)确定和量化EGF和相关生长因子在ASDN中ENaC活性的生理调节中的作用，并确定该途径在盐敏感性高血压发生中的作用；2)建立RhoGDI和Rac1在ENaC调控中的生理作用，确定Rac1在介导EGF对ENaC影响中的作用；3)定义Rac1调节ENaC活性的细胞和分子机制：WAVEs是否将Rac1调节传递给ENaC？