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）：血压的长期控制涉及Na+稳态，通过对醛固酮敏感的远端肾单位（ASDN）中上皮上皮Na+通道（ENAC）的精确调节。 ENAC功能障碍是导致全身Na+水平的干扰，与血液体积，血压和肺液平衡异常相关的障碍。我们提供了初步证据，表明表皮生长因子（EGF）可以用作ENAC配体，并假设EGF家庭和Rac1的成员在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及其相关的EGF家庭成员与ERBB受体结合，并充当负责肾脏发育，生理和病理生理学的信号因素。在生理条件下，ERBB受体在调节肾脏的肾脏血流动力学和电解质处理中起重要作用，而在不同的病理生理状态下，ERBB激活可能介导对肾脏的有益或有害作用。 ERBB受体的刺激激活了涉及小GTPase的细胞内级联反应，尤其是Rac1。小的G蛋白及其调节蛋白有助于肾脏和心血管疾病的病理。我们的初步结果，包括使用孤立的，开放式ASDN的电生理实验，表明ENAC受EGF和Rac1的调节，可能是通过收敛机制来调节的。这些研究中使用的DAHL盐敏感（SS）大鼠在高盐饮食上会出现严重的高血压。我们提供了初步数据，表明ENAC有助于SS大鼠菌株中高血压的发展。此外，我们的初步数据表明，SS大鼠的EGF浓度降低，我们建议这将增强ENAC活性，钠保留和高血压。在此初步数据和我们先前发表的发现的基础上，该提案的具体目标是确定通过RAC1作用的EGF是否对通过调节ENAC进行调节并定义EGF和Rac1介导的ENAC活性中EGF和Rac1介导的变化的精确机制对肾脏钠处理的生理控制是否重要。该提案中将使用电生理，免疫组织化学，生化，显微镜和体外研究的慢性研究和体外研究，以提供有关EGF-Family和RAC1成员如何调节ENAC的机械见解，以及该途径的变化如何导致SSS ss ss ss ss at s ss ss ss ss ss ss ss ss ss sss ad tage的变化。这些研究将针对三个具体目的：1）识别和量化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高血压发展中的作用； 2）确定Rhogdi和Rac1在调节ENAC中的生理作用，并确定RAC1在介导EGF对ENAC效应中的作用； 3）定义RAC1调节ENAC活性的细胞和分子机制：波是否将Rac1调节传达给ENAC？