Schnurri-3 Inhibitors: specific inducers of adult bone formation

描述（由申请人提供）：在正常的生理状态下，骨骼系统提供活动能力，保护重要器官，并作为造血发生的必要环境。为了实现这些功能，骨骼存在于一个动态平衡中，其特征是破骨细胞介导的骨吸收和成骨细胞介导的骨沉积[2]。这种体内平衡重塑的维持在衰老过程中被破坏，导致骨质流失，即骨质疏松症，在美国有超过1000万人受到骨质疏松症的影响。随着个体年龄的增长，这种疾病的进展导致骨折的发生率增加，从而导致严重的健康后果[10]。由于预防或治疗骨质疏松症的治疗方法很少，我们的目标是开发新的基于机制的治疗方法，以增加合成代谢骨形成和防止骨质流失。我们最近发现Schnurri-3 （Shn3）是Schnurri大锌指蛋白家族的一员，是成人骨形成[5]的重要调节因子。我们对携带Shn3零突变的小鼠（Shn3-/-小鼠）的代和后续分析显示，通过增强成骨细胞活性产生了深刻的高骨量表型，其特征是骨形成率大大增加。在Shn3-/-小鼠中观察到的骨硬化表型不影响骨骼形态，因为它是在出生后发生的。然而，Shn3的缺失使这些小鼠无法像对照组小鼠那样发生与年龄相关的骨丢失。Shn3-/-骨的特点：增加骨合成代谢活性，保持正常形态发生，矿化和生物物理特性，表明该蛋白是治疗某些骨骼疾病的理想治疗靶点。不幸的是，对Shn3的结构分析表明，该蛋白缺乏适合药物靶向的功能域。然而，我们已经证明shRNA靶向Shn3的3'UTR可在体外降低蛋白水平并增强成骨细胞功能。此外，我们已经确定Shn3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检测方法，通过靶向该基因3'UTR的转录后机制，鉴定出选择性降低Shn3蛋白水平的化学探针。鉴定降低Shn3水平的化合物将为预防与骨质疏松症相关的破坏性骨质流失提供有价值的治疗方法。

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