Eph Kinase Signaling In Renal Epithelial Cells

描述（由申请人提供）：Eph激酶的14个成员构成了哺乳动物系统中最大的受体酪氨酸激酶亚家族，并结合称为ephrin的膜锚定配体。Eph/ephrin相互作用在调节神经和心血管系统发育中的关键作用已得到充分证实。然而，它们是否也有上皮细胞的发育在很大程度上仍未被研究。申请人发表的初步结果表明，Eph激酶是上皮分支形态发生的新型调节剂。在MDCK肾上皮细胞中，内源性EphA2的配体激活能有效抑制HGF/ sf诱导的三维胶原凝胶中的分支形态发生。在体内胚胎肾中，EphA2在输尿管芽（UB）中选择性表达，而ephrin-A1在肾后间质（MM）中优先表达。我们假设局部Eph/ephrin相互作用的UB/MM边界允许接触依赖的肾分支形态发生指导。支持这一假设的是，EphA2基因敲除小鼠的肾脏出现了异常的分支形态发生。本提案的目标是利用我们已经建立的独特模型系统来确定Eph激酶调节肾脏发育的细胞和分子基础。在目的1中，我们将建立在后肾发育过程中所有主要EphA激酶和ephrin-As的时空表达谱。在Aim 2中，我们将通过创建EphA1/EphA2化合物敲除，重点关注EphA/ephrin-A相互作用的扰动如何影响体内肾脏形态发生。具体目标3，我们将使用体外肾上皮细胞来深入了解EphA激酶如何调节e -钙粘蛋白介导的细胞-细胞粘附和信号传导。这项研究的完成将填补我们对后肾发育过程中肾上腺素-ephrin相互作用的理解空白。了解UB分支形态发生机制不仅具有发育意义，而且具有重要的医学意义。异常的分支形态发生可导致肾发育不全和输尿管定位不全或重复，这是常见的出生缺陷。UB生长和分支中更细微的缺陷可能导致肾单位数量减少，这可能使个体在以后的生活中易患肾脏疾病，包括高血压。提出的研究可能会导致一种新的方式来调节肾细胞的行为，以治疗肾脏疾病。这一建议的完成将填补我们对肾上腺素-ephrin相互作用在肾脏发育中的作用的理解的空白。了解UB分支形态发生机制不仅具有发育意义，而且具有重要的医学意义。异常的分支形态发生可导致肾发育不全和输尿管定位不全或重复，这是常见的出生缺陷。UB生长和分支中更细微的缺陷可能导致肾单位数量减少，这可能使个体在晚年易患肾脏疾病，包括高血压和终末期肾脏疾病。提出的研究可能会导致一种新的方式来调节肾细胞的行为，以治疗肾脏疾病。公共卫生相关性：该建议的完成将填补我们对肾上腺素相互作用在肾脏发育中的作用的理解空白。了解UB分支形态发生机制不仅具有发育意义，而且具有重要的医学意义。异常的分支形态发生可导致肾发育不全和输尿管定位不全或重复，这是常见的出生缺陷。UB生长和分支中更细微的缺陷可能导致肾单位数量减少，这可能使个体在晚年易患肾脏疾病，包括高血压和终末期肾脏疾病。提出的研究可能会导致一种新的方式来调节肾细胞的行为，以治疗肾脏疾病。

DESCRIPTION (provided by applicant): The 14 members of Eph kinases constitute the largest subfamily of receptor tyrosine kinases in mammalian system and bind membrane-anchored ligands called ephrins. The pivotal role of Eph/ephrin interactions in regulating development of nervous and cardiovascular systems is well substantiated. However, whether they also epithelial development remains largely unexplored. The published and preliminary results by the applicant show that Eph kinases are novel regulators of epithelial branching morphogenesis. In MDCK renal epithelial cells, ligand activation of endogenous EphA2 potently inhibited HGF/SF-induced branching morphogenesis in 3-D collagen gels. In embryonic kidneys in vivo, EphA2 was selectively expressed in ureteric bud (UB), while ephrin-A1 was preferentially expressed in surrounding metanephric mesenchyme (MM). We hypothesize that the localized Eph/ephrin interactions UB/MM boundary allows contact-dependent guidance of renal branching morphogenesis. Supporting this hypothesis, kidneys from EphA2 knockout mice showed abnormal branching morphogenesis. The goal of this proposal is to take advantage of the unique model systems that we have established to determine the cellular and molecular bases underlying Eph kinase regulation of kidney development. In Aim 1, we will establish spatiotemporal expression profiles of all major EphA kinases and ephrin-As during metanephric kidney development. In Aim 2, we will focus on how perturbations of EphA/ephrin-A interactions will affect renal morphogenesis in vivo, by creating EphA1/EphA2 compound knockout. Specific Aim 3, we will use renal epithelial cell in vitro to gain insights on how EphA kinases regulate E-cadherin-mediated cell-cell adhesion and signaling. Completion of this proposal will fill a gap in our understanding on the role of Eph-ephrin interactions in the development metanephric kidney. Understanding mechanisms of UB branching morphogenesis has not only developmental significance, but also medical importance. Abnormal branching morphogenesis can lead to renal agenesis and malpositioning or duplication of the ureter, which are common birth defects. More subtle defects in UB growth and branching may result in reduced nephron number, which may predispose individuals to renal diseases later in life, including hypertension. The proposed studies can potentially lead to a new way to modulate kidney cell behaviors for the treatment of kidney diseases.Completion of this proposal will fill a gap in our understanding on the role of Eph-ephrin interactions in the development of the kidney. Understanding mechanisms of UB branching morphogenesis has not only developmental significance, but also medical importance. Abnormal branching morphogenesis can lead to renal agenesis and malpositioning or duplication of the ureter, which are common birth defects. More subtle defects in UB growth and branching may result in reduced nephron number, which may predispose individuals to renal diseases later in life, including hypertension and end stage renal disease. The proposed studies can potentially lead to a new way to modulate kidney cell behaviors for the treatment of kidney diseases. PUBLIC HEALTH RELEVANCE: Completion of this proposal will fill a gap in our understanding on the role of Eph-ephrin interactions in the development of the kidney. Understanding mechanisms of UB branching morphogenesis has not only developmental significance, but also medical importance. Abnormal branching morphogenesis can lead to renal agenesis and malpositioning or duplication of the ureter, which are common birth defects. More subtle defects in UB growth and branching may result in reduced nephron number, which may predispose individuals to renal diseases later in life, including hypertension and end stage renal disease. The proposed studies can potentially lead to a new way to modulate kidney cell behaviors for the treatment of kidney diseases.