MECHANISMS RESPONSIBLE FOR GENOMIC INSTABILITY IN PREMATURE AGING LAMINOPATHIES

导致过早衰老核纤层蛋白病基因组不稳定的机制

• 批准号: 8513177
• 负责人: Susana Gonzalo Hervas
• 金额: $ 14.91万
• 依托单位: SAINT LOUIS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8513177
• 关键词: MECHANISMS; RESPONSIBLE; GENOMIC; INSTABILITY; PREMATURE

DESCRIPTION (provided by applicant): A-type lamins are intermediate filament proteins that provide a scaffold for tethering chromatin and protein complexes regulating nuclear structure and function. Interest in lamins increased after the association of mutations in the LMNA gene with a variety of degenerative disorders broadly termed laminopathies, cancer and aging. The causal relationship between alterations of A-type lamins and disease and the molecular pathways involved are poorly understood. Our data revealed novel functions for A-type lamins in the maintenance of telomeres and in the stabilization of 53BP1, a mediator in the DNA damage response pathway. Loss of A-type lamins leads to telomere shortening, telomeric chromatin defects, impaired DNA repair, increased genomic instability, and defects in the non-homologous end-joining of dysfunctional telomeres, a process that requires 53BP1. Some of these phenotypes would be consistent with 53BP1 deficiency. In support of this notion, reconstitution of 53BP1 into A-type lamins-deficient cells rescued defects in DNA repair. Elucidating molecular mechanism responsible for degradation of 53BP1 might provide novel targets for therapy. Our preliminary data indicates that 53BP1 is degraded by the protease Cathepsin L and by the proteasome. Interestingly, a mouse model of progeria (Zmpste24-/-) shown to markedly upregulate Cathepsin L, exhibits low levels of 53BP1, suggesting that deregulation of the Cathepsin L-mediated degradation of 53BP1 might be a common event in laminopathies. Importantly, we found that treatment with vitamin D, a known activator of Cystatin D [8], the endogenous inhibitor of Cathepsin L, rescues 53BP1 levels, providing a putative strategy to prevent 53BP1 degradation, ameliorating phenotypes of laminopathies. The hypothesis to be tested is that alterations in A-type lamins causing upregulation of Cathepsin L lead to destabilization of 53BP1 protein and defects in DNA repair and telomere stability, contributing to genomic instability and the phenotypes of some lamin-related diseases. Our hypothesis will be tested under three specific aims. Under Aim 1, we will elucidate the molecular mechanisms leading to destabilization of 53BP1 in laminopathies and evaluate ways to target this pathway and improve DNA repair. Under Aim 2, we will determine the extent to which deregulation of the Cathepsin L/53BP1 pathway in laminopathies affects telomere stability. Under Aim 3, we will determine whether regulation of the Cathepsin L/53BP1 pathway by vitamin D ameliorates the pathophysiology of lamin-related diseases in vivo. The studies performed here will be of significance not only for elucidating the molecular mechanisms by which A-type lamins impact on telomere function and DNA repair, but also for understanding the underlying basis of the pathophysiology of lamin-related diseases, including degenerative laminopathies, premature aging syndromes and cancer. The results of our study could translate into the development of novel therapeutic strategies that target 53BP1 degradation pathway to improve the phenotypes associated to these diseases. PUBLIC HEALTH RELEVANCE: Understanding the cellular functions of A-type lamins, structural components of the nucleus, has become a highly topical subject due to their implication in a number of degenerative disorders broadly named laminopathies, as well as in cancer and aging. The molecular pathways by which defects in A-type lamins contribute to disease are poorly understood. Genomic instability caused by defective repair of DNA damage has been proposed to contribute to the pathogenesis of laminopathies. This proposal aims to unravel molecular mechanisms that are altered upon loss of A-type lamins leading to increased genomic instability. In addition, we will evaluate ways to target these molecular mechanisms with the goal of identifying treatments that ameliorate the phenotypes of laminopathies. Both, studies with primary cells (in vitro) and with mouse models of laminopathies (in vivo) will be conducted. The knowledge obtained from this research will be of great possible significance for the development of therapeutic approaches to treat lamin-related diseases.

描述（由申请人提供）：A 型核纤层蛋白是中间丝蛋白，为束缚染色质和调节核结构和功能的蛋白质复合物提供支架。在 LMNA 基因突变与多种退行性疾病（广泛称为核纤层蛋白病、癌症和衰老）相关之后，人们对核纤层蛋白的兴趣增加了。 A 型核纤层蛋白的改变与疾病之间的因果关系以及所涉及的分子途径知之甚少。我们的数据揭示了 A 型核纤层蛋白在维持端粒和稳定 53BP1（DNA 损伤反应途径中的介质）方面的新功能。 A 型核纤层蛋白的缺失会导致端粒缩短、端粒染色质缺陷、DNA 修复受损、基因组不稳定性增加以及功能失调端粒的非同源末端连接缺陷，这一过程需要 53BP1。其中一些表型与 53BP1 缺陷一致。为了支持这一观点，将 53BP1 重建到 A 型核纤层蛋白缺陷细胞中可以挽救 DNA 修复缺陷。阐明 53BP1 降解的分子机制可能为治疗提供新的靶点。我们的初步数据表明 53BP1 被蛋白酶组织蛋白酶 L 和蛋白酶体降解。有趣的是，早衰症小鼠模型 (Zmpste24-/-) 显示组织蛋白酶 L 显着上调，且 53BP1 水平较低，这表明组织蛋白酶 L 介导的 53BP1 降解失调可能是核纤层蛋白病中的常见事件。重要的是，我们发现维生素 D（一种已知的半胱氨酸蛋白酶抑制剂 D 激活剂 [8]（组织蛋白酶 L 的内源性抑制剂）治疗可恢复 53BP1 水平，为防止 53BP1 降解、改善核纤层蛋白病的表型提供了一种假定的策略。待检验的假设是，A 型核纤层蛋白的改变导致组织蛋白酶 L 上调，导致 53BP1 蛋白不稳定以及 DNA 修复和端粒稳定性缺陷，从而导致基因组不稳定和一些核纤层蛋白相关疾病的表型。我们的假设将在三个具体目标下进行检验。在目标 1 下，我们将阐明导致核纤层蛋白病中 53BP1 不稳定的分子机制，并评估靶向该途径和改善 DNA 修复的方法。在目标 2 下，我们将确定核纤层蛋白病中组织蛋白酶 L/53BP1 通路的失调对端粒稳定性的影响程度。在目标 3 下，我们将确定维生素 D 对组织蛋白酶 L/53BP1 途径的调节是否可以改善体内核纤层蛋白相关疾病的病理生理学。这里进行的研究不仅对于阐明A型核纤层蛋白影响端粒功能和DNA修复的分子机制具有重要意义，而且对于了解核纤层蛋白相关疾病（包括退行性核纤层蛋白病、早衰综合征和癌症）的病理生理学基础具有重要意义。我们的研究结果可以转化为针对 53BP1 降解途径的新型治疗策略的开发，以改善与这些疾病相关的表型。 公共健康相关性：了解 A 型核纤层蛋白（细胞核的结构成分）的细胞功能已成为一个高度热门的主题，因为它们与许多广泛称为核纤层蛋白病的退行性疾病以及癌症和衰老有关。 A 型核纤层蛋白缺陷导致疾病的分子途径尚不清楚。 DNA 损伤修复缺陷引起的基因组不稳定性被认为是核纤层蛋白病的发病机制之一。该提案旨在揭示 A 型核纤层蛋白丢失后发生改变导致基因组不稳定性增加的分子机制。此外，我们将评估针对这些分子机制的方法，目的是确定改善核纤层蛋白病表型的治疗方法。将使用原代细胞（体外）和小鼠核纤层蛋白病模型（体内）进行研究。从这项研究中获得的知识对于开发治疗核纤层蛋白相关疾病的治疗方法具有重要意义。