Inhibitors of BMP-1/TLD proteases as novel therapeutics for muscular dystrophy

说明(申请人提供)：肌肉生长抑制素(MSTN)是一种分泌型蛋白质，通常作用于抑制肌肉生长。缺乏MSTN活性的基因工程小鼠由于肌肉纤维肥大和纤维数量增加的组合，肌肉质量急剧增加。此外，给野生型小鼠注射一些不同的MSTN抑制剂也可以促进肌肉生长，这表明MSTN在成年动物的肌肉生长调节中起着关键作用。因此，人们对MSTN信号的抑制剂可能有效地增强肌肉退行性疾病患者的肌肉力量和再生的可能性有相当大的兴趣。在处理MSTN前体蛋白后，成熟的C-末端二聚体仍然与N-末端前肽非共价结合，从而使MSTN处于不活跃的潜伏状态。大量的生化和遗传学研究表明，BMP-1/Tolloid金属蛋白水解酶家族的成员通过裂解并使前肽失活，在调节MSTN潜伏期方面起着关键作用。因此，抑制这些酶可能是一种有效的治疗策略，以防止潜伏性MSTN的激活，从而促进肌肉生长。此外，靶向这些蛋白酶的潜在好处可能远远超出MSTN的抑制，因为这些蛋白酶也已知作用于除MSTN之外的其他底物，这些底物可能在肌肉退行性疾病中发挥作用。具体地说，这些酶能够裂解转化生长因子-ss结合蛋白LTBP-1，从而从潜伏期激活转化生长因子-生长因子，这对于治疗发展可能是重要的，因为抑制转化生长因子-生长因子信号已被证明改善了mdx小鼠的肌肉再生。此外，BMP-1/Tolloid蛋白酶似乎是负责将前胶原加工成能够形成胶原纤维的成熟物种的酶，增加了这些酶可能在各种疾病背景下的纤维化发展中发挥作用的可能性。因此，BMP-1/Tolloid蛋白水解酶的抑制剂通过靶向几种不同的分子途径，有可能为肌肉退行性疾病患者提供临床益处。该项目的总体目标是验证抑制BMP-1/Tolloid蛋白水解酶在肌肉退行性变中的有益效果，并启动能够靶向这些酶的生物制剂的开发。具体目的是：评估靶向BMP-1/tolloid金属蛋白酶在mdx小鼠中的潜在益处，并确定BMP-1/tolloid抑制剂SFRP2在骨骼肌中以转基因形式表达或全身给药时是否可以促进肌肉生长。如果成功，这些研究将确定一种新的治疗剂，具有促进肌肉生长和改善肌肉营养不良患者的临床结果的潜力。 与公共健康相关：肌肉生长抑制素是一种蛋白质，通常会限制肌肉生长。该项目的目标是开发能够阻断肌肉退行性疾病患者肌肉抑制素活性并促进肌肉生长的治疗剂。

DESCRIPTION (provided by applicant): Myostatin (MSTN) is a secreted protein that normally acts to suppress muscle growth. Mice genetically engineered to lack MSTN activity have dramatic increases in muscle mass as a result of a combination of muscle fiber hypertrophy and increased fiber numbers. Moreover, administration of a number of different MSTN inhibitors to wild type mice can also promote muscle growth, demonstrating that MSTN plays a critical role in regulating muscle growth in adult animals. As a result, there has been considerable interest in the possibility that inhibitors of MSTN signaling might be effective in enhancing muscle strength and regeneration in patients with muscle degenerative diseases. Following processing of the MSTN precursor protein, the mature C-terminal dimer remains non-covalently bound to the N-terminal propeptide, which maintains MSTN in an inactive, latent state. A variety of biochemical and genetic studies have demonstrated that members of the BMP-1/tolloid family of metalloproteases play a critical role in regulating MSTN latency by cleaving and thereby inactivating the propeptide. Hence, inhibition of these proteases could be an effective therapeutic strategy to prevent activation of latent MSTN and thereby promote muscle growth. Moreover, the potential benefits of targeting these proteases could extend well beyond just MSTN inhibition, as these proteases are also known to act on other substrates besides MSTN that may play a role in muscle degenerative diseases. In particular, these proteases are capable of cleaving the TGF-ss binding protein, LTBP-1, thereby activating TGF-ss from its latent state, which may be significant with respect to therapeutic development given that inhibition of TGF-ss signaling has been shown to improve muscle regeneration in mdx mice. Furthermore, the BMP-1/tolloid proteases appear to be the enzymes responsible for processing procollagens into the mature species capable of forming collagen fibrils, raising the possibility that these enzymes may play a role in the development of fibrosis in a variety of disease settings. Hence, inhibitors of BMP-1/tolloid proteases have the potential to provide clinical benefit in patients with muscle degenerative diseases by targeting several different molecular pathways. The overall aims of this project are to validate the beneficial effects of inhibiting BMP-1/tolloid proteases in the setting of muscle degeneration and to initiate the development of a biologic agent capable of targeting these enzymes. The Specific Aims are: to assess the potential beneficial effects of targeting BMP-1/tolloid metalloproteases in mdx mice and to determine whether the BMP-1/tolloid inhibitor, sFRP2, can increase muscle growth either when expressed as a transgene in skeletal muscle or when administered systemically to mice. If successful, these studies will identify a novel therapeutic agent with the potential to promote muscle growth and improve clinical outcome in patients with muscular dystrophy. PUBLIC HEALTH RELEVANCE: Myostatin is a protein that normally acts to limit muscle growth. The goal of this project is to develop therapeutic agents capable of blocking myostatin activity and promoting muscle growth in patients with muscle degenerative diseases.