Schnurri-3 Inhibitors: specific inducers of adult bone formation

描述（由申请人提供）：在正常生理状态下，骨骼系统提供活动性，保护重要器官，并作为造血发生的基本环境[1]。为了实现这些功能，骨骼处于动态平衡状态，其特征在于持续的破骨细胞介导的骨吸收和成骨细胞介导的骨沉积[2]。这种稳态重塑的维持在衰老过程中被破坏，导致衰弱性骨丢失，称为骨质疏松症，在美国影响超过1000万人[3]。随着个体年龄的增长，这种疾病的进展导致骨折发生率增加，导致严重的健康后果[4]。由于很少有治疗选择可用于预防或治疗骨质疏松症，我们的目标是开发新的机制为基础的治疗，增加合成代谢骨形成和防止骨丢失。我们最近鉴定了Schnurri-3（Shn 3），Schnurri大锌指蛋白家族的成员，作为成人骨形成的重要调节因子[5]。我们对Shn 3无效突变小鼠（Shn 3-/-小鼠）的一代和随后的分析揭示了一种深刻的高骨量表型，这种表型通过增强成骨细胞活性而产生，其特征在于骨形成速率大大增加。在Shn 3-/-小鼠中观察到的成骨细胞表型不影响骨骼形态，因为其发生在出生后。然而，Shn 3的缺失使这些小鼠对对照小鼠中发生的与年龄相关的骨丢失难以抵抗。Shn 3-/-骨的特征：增加的骨合成代谢活性，保持正常的形态发生，矿化和生物物理特性，表明这种蛋白质是治疗某些骨骼疾病的理想治疗靶点。不幸的是，Shn 3的结构分析揭示了该蛋白质内缺乏适合于药物靶向的功能结构域。然而，我们已经证明，靶向Shn 3的3 'UTR的shRNA在体外降低了蛋白水平并增强了成骨细胞功能。此外，我们已经确定，Shn 3的转录后阻断导致体内骨量增加。因此，我们设计了一系列基于细胞的测定，其将允许鉴定通过靶向该基因的3 'UTR的转录后机制选择性降低Shn 3蛋白水平的化学探针。鉴定降低Shn 3水平的化合物将提供有价值的治疗方法来预防与骨质疏松症相关的破坏性骨丢失。 公共卫生相关性：骨质疏松症是一种使骨骼系统衰弱的疾病，目前在美国影响超过1000万人。疾病进展导致骨折发生率增加，导致严重的健康后果，并将成为全球老龄化人群中发病率和死亡率的扩大来源。虽然有几类药物可用于预防骨质疏松症或癌症背景下的骨丢失或增加骨形成，但由于毒副作用，不耐受或高昂的成本，目前的治疗方法远非理想。该提案的最终目标是开发基于机制的治疗方法，以防止骨丢失并增加合成代谢骨形成。2

DESCRIPTION (provided by applicant): In a normal physiological state the skeletal system provides mobility, protection for vital organs and serves as an essential environment in which hematopoiesis can occur [1]. To achieve these functions, the skeleton exists in a dynamic equilibrium characterized by continuous osteoclast-mediated resorption of bone and osteoblast- mediated bone deposition [2]. Maintenance of this homeostatic remodeling is disrupted during aging leading to debilitating bone loss referred to as osteoporosis that affects over 10 million individuals in the United States [3]. As an individual ages, the progression of this disease results in an increased incidence of fracture that results in serious health consequences [4]. Since few therapeutic options are available for the prevention or treatment of osteoporosis, our goal is to develop novel mechanism-based treatments that increase anabolic bone formation and prevent bone loss. We have recently identified Schnurri-3 (Shn3), a member of the Schnurri family of large zinc-finger proteins, as an essential regulator of adult bone formation [5]. Our generation and subsequent analysis of mice bearing a null mutation in Shn3 (Shn3-/- mice) revealed a profound high-bone mass phenotype that arises through augmented osteoblast activity and is characterized by greatly increased rates of bone formation. The osteosclerotic phenotype observed in Shn3-/- mice does not affect skeletal morphology since its onset is postnatal. However, the loss of Shn3 renders these mice refractory to the age-associated loss in bone that occurs in control mice. The characteristics of Shn3-/- bone: increased bone anabolic activity, preservation of normal morphogenesis, mineralization and biophysical properties suggest that this protein is an ideal therapeutic target for the treatment of certain skeletal disorders. Unfortunately, structural analysis of Shn3 has revealed a dearth of functional domains within this protein that are suitable for drug targeting. We have, however, demonstrated that shRNA targeting of the 3'UTR of Shn3 reduces protein levels and augments osteoblast function in vitro. Furthermore, we have determined that post-transcriptional blockade of Shn3 results in increased bone mass in vivo. Therefore, we have designed a series of cell-based assays that will allow for the identification of chemical probes that selectively reduce Shn3 protein levels through a post- transcriptional mechanism targeting the 3'UTR of this gene. The identification of compounds that decrease Shn3 levels would provide a valuable therapeutic approach to prevent the destructive bone loss associated with osteoporosis. PUBLIC HEALTH RELEVANCE: Osteoporosis is a debilitating disease of the skeletal system that currently affects over 10 million individuals in the United States. Disease progression results in an increased incidence of fracture that results in serious health consequences and will present an expanding source of morbidity and mortality in an aging global population. While a few classes of medications are available to either prevent bone loss or increase bone formation in the setting of osteoporosis or cancer, current therapeutics are far from ideal due to toxic side effects, intolerance, or prohibitive cost. The ultimate goal of this proposal is to develop mechanism-based treatments to prevent bone loss and to increase anabolic bone formation. 2