Mechanisms Leading to Adrenal Zonation

描述（由申请人提供）：人肾上腺皮质可分为不同的区域，这些区域具有形态学和生物化学差异。醛固酮的生产在小球和皮质醇的皮质束状体中，可以追溯到区域特异性表达的酶参与类固醇的生物合成。这对于醛固酮合酶（CYP 11B 2）和112-羟化酶（CYP 11B 1）尤其如此。我们的初步数据表明，三种核激素受体在决定球状体与束状体表型中起着关键作用。在这里，我们测试的总体假设，区域特异性表达的CYP 11B 2和CYP 11B 1的结果从相反的活动的核激素受体之间的不同的球状体和束状体。该假设将通过四个特定目的中提出的研究进行检验：特定目的1中提出的实验将扩展申请人正在进行的项目，该项目已确定了CYP 11B 2基因5 '侧翼区的调控元件。拟定的研究将完成负责肾小球特异性表达CYP 11B 2的反式作用因子的定义。重点将放在核受体的作用，NR 4A 2，它刺激CYP 11B 2启动子活性，是由血管紧张素II上调，主要在肾小球。具体目标二将确定的机制，负责缺乏CYP 11B 2的肾小球。初步研究表明，核受体类固醇生成因子1（SF-1; NR 5A 1）是CYP 11B 2的强效阻遏物，但也是CYP 11B 1的强效激活剂。这些数据支持SF-1活性的作用，在球状到束状的过渡。特定目标3将确定核激素受体翻译后修饰在肾小球细胞表型发育中的作用。初步数据表明，球状体具有升高的SUMO化活性，SF-1的SUMO化调节其活性。具体目标4将定义负责在束状体中沉默CYP 11B 2表达的顺式调节元件和反式作用因子。我们已经分离出一个100 bp的插入片段，它存在于CYP 11B 2基因中，但不存在于CYP 11B 1基因中。初步的数据支持的可能性，该插入包括沉默序列，其作用是阻止束状细胞表达的CYP 11B 2。原发性醛固酮增多症（PA）估计发生在8%的高血压人群中.大多数PA病例是由结节性增生或醛固酮腺瘤引起的。CYP 11B 2表达的正常调节中断似乎是这种疾病过程的重要组成部分。拟议的研究将提供一个详细的了解的分子机制，调节CYP 11B 2在正常肾上腺的表达，并应提供深入了解醛固酮过多的疾病，包括醛固酮增多症。公共卫生相关性：从这些研究中获得的信息将确定引起CYP 11B 2和CYP 11B 1区域特异性表达的分子机制，从而促进我们对肾上腺区域化的理解。此外，拟议的研究将有助于更好地确定肾上腺类固醇过量疾病的原因，包括醛固酮增多症。

DESCRIPTION (provided by applicant): The human adrenal cortex can be divided into distinct zones that have both morphologic and biochemical differences. The production of aldosterone in the zona glomerulosa and cortisol in the zona fasciculate can be traced to the zone-specific expression of the enzymes involved in steroid biosynthesis. This is particularly true for aldosterone synthase (CYP11B2) and 112-hydroxylase (CYP11B1). Our preliminary data suggest that three nuclear hormone receptors play pivotal roles in determining a glomerulosa versus fasciculata phenotype. Herein, we test the overall hypothesis that zone-specific expression of CYP11B2 and CYP11B1 results from the opposing activities of nuclear hormone receptors that differ between the glomerulosa and fasciculata. This hypothesis will be tested by the studies proposed in four Specific Aims: The experiments proposed in Specific Aim One will extend the applicant's ongoing project that has defined the regulatory elements in the 5'-flanking region of CYP11B2 gene. The proposed studies will complete the definition of the trans-acting factors responsible for glomerulosa specific expression of CYP11B2. Focus will be placed on the role of nuclear receptor, NURR1 (NR4A2), which stimulates CYP11B2 promoter activity, is up-regulated by angiotensin II and is expressed primarily in the zona glomerulosa. Specific Aim Two will determine the mechanisms responsible for the lack of CYP11B2 seen in the glomerulosa. Preliminary studies indicate that the nuclear receptor, steroidogenic factor 1 (SF-1; NR5A1) is a potent repressor of CYP11B2 but potent activator of CYP11B1. These data support a role for SF-1 activity in the transition of glomerulosa to fasciculata. Specific Aim 3 will determine the role of nuclear hormone receptor post-translational modification in the development of a glomerulosa cell phenotype. Preliminary data indicate that the glomerulosa has elevated sumoylation activities and sumoylation of SF-1 regulates its activity. Specific Aim 4 will define the cis-regulatory elements and trans-acting factors responsible for silencing CYP11B2 expression in the fasciculata. We have isolated a 100 bp insert that is present in the CYP11B2 but not CYP11B1 gene. Preliminary data support the possibility that this insert includes a silencer sequence that acts to block fasciculata cell expression of CYP11B2. SIGNIFICANCE: Primary aldosteronsism (PA) is estimated to occur in 8 % of the hypertensive population. Most PA cases are caused by nodular hyperplasia or aldosterone-producing adenoma. A disruption in the normal regulation of CYP11B2 expression appears to be an important part of this disease process. The proposed studies will provide a detailed understanding of the molecular mechanisms regulating CYP11B2 expression within the normal adrenal and should provide insight into diseases of aldosterone excess including hyperaldosteronism. PUBLIC HEALTH RELEVANCE: Narrative Information obtained from these studies will determine the molecular mechanisms causing zone- specific expression of CYP11B2 and CYP11B1 thereby advancing our understanding of adrenal zonation. In addition, the proposed studies will help to better define the causes of diseases of adrenal steroid excess including hyperaldosteronism.