Targeting the lysosome-mitochondria axis in neurodegenerative lysosomal storage diseases - Lessons from telomerase immortalization

我们已经确定了端粒酶永生化和NPC1纠正之间的联系 脂肪储存表型。此外，我们最近发现了应激转录 因子NRF1作为端粒酶诱导的基因之一，特别是在已经 在尼曼-皮克C病等应激状态下，以溶酶体为特征的细胞 胆固醇储存。这些结果特别令人兴奋，因为在许多细胞 分配给NRF1的功能最近被证明是蜂窝网络中的核心角色 胆固醇动态平衡。 我们随后确定，NRF1的异位表达单独可以纠正 NPC1胆固醇储存表型提示NRF1在 线粒体和溶酶体功能以及在应激(疾病)条件下NRF1可以 使他们的功能正常化。因此，我们确定了一种转录因子，它是一种新的 NPC1疾病的靶点，以及许多其他溶酶体储存障碍的潜在靶点。 然而，众所周知，转录因子很难下药和 由于其严格且往往错综复杂的监管，它们面临着独特的挑战。为了这些 我们之所以兴奋地发现了两种激活靶标中NRF1的独特方法， 疾病细胞。首先，使用我们开发的一种新的转录激活分析方法 已经确定了一组FDA批准的钙通道抑制剂，它们非常有效 NRF1的激活物。第二，我们发现了端粒酶的一种有趣的特性 永生化的NPC1细胞；它们分泌的外体含有高水平的活性NRF1 能够将该转录因子转移到靶细胞。 通过靶向NRF1，该提案的目标是首先验证其治疗作用 有可能治疗NPC1疾病，从而解决一个巨大的未得到满足的需求。第二，到 用NPC1病的动物模型在体内评价其治疗效果。 这些研究的成功将为这一新方法提供临床前验证。 并为进一步的治疗开发提供了理论基础。

We have identified a link between telomerase immortalization and correction of the NPC1 lipid storage phenotype. Furthermore, we have recently identified the stress transcription factor NRF1 as one of the genes induced by telomerase, especially in cells that are already under stress such as Niemann-Pick C disease cells characterized by lysosomal cholesterol storage. These results are particularly exciting since among many cellular functions assigned to NRF1 it was recently shown to be a central player in cellular cholesterol homeostasis. We subsequently determined that ectopic expression of NRF1 alone could correct the NPC1 cholesterol storage phenotype suggesting that NRF1 provides a link between mitochondria and lysosome function and under stress (disease) conditions NRF1 could normalize their function. Thus, we have identified a transcription factor that is a novel target for NPC1 disease and potentially for many other lysosomal storage disorders. It is known however, that transcription factors are notoriously difficult to drug and present unique challenges due to their tight and often intricate regulation. For these reasons we were excited to identify two unique methods for activating NRF1 in target, disease cells. First, using a novel transcriptional activation assay we have developed we have identified a group of FDA-approved calcium channel inhibitors that are very potent activators of NRF1. Second, we have identified an interesting property of telomerase immortalized NPC1 cells; they secreted exosomes that contain high levels of active NRF1 that are capable of transferring this trasncription factor to target cells. By targeting NRF1, the goals of this proposal are first to validate its therapeutic potential to treat NPC1 disease and thus address a great-unmet need. Second, to evaluate their therapeutic effectiveness in vivo using an animal model of NPC1 disease. The success of these studies will provide preclinical validation of this novel approach and provide the rationale for further therapeutic development.