Small-molecule Activation of TFEB Alleviates Niemann-Pick Disease Type C via Promoting Lysosomal Exocytosis and Biogenesis

Niemann–Pick disease type C (NPC) is a devastating lysosomal storage disease characterized by abnormal cholesterol accumulation in lysosomes. Currently, there is no treatment for NPC. Transcription factor EB (TFEB), a member of the microphthalmia transcription factors (MiTF), has emerged as a master regulator of lysosomal function and promoted the clearance of substrates stored in cells. However, it is not known whether TFEB plays a role in cholesterol clearance in NPC disease. Here, we show that transgenic overexpression of TFEB, but not TFE3 (another member of MiTF family) facilitates cholesterol clearance in various NPC1 cell models. Pharmacological activation of TFEB by sulforaphane (SFN), a previously identified natural small-molecule TFEB agonist by us, can dramatically ameliorate cholesterol accumulation in human and mouse NPC1 cell models. In NPC1 cells, SFN induces TFEB nuclear translocation via a ROS-Ca2+-calcineurin dependent but MTOR-independent pathway and upregulates the expression of TFEB-downstream genes, promoting lysosomal exocytosis and biogenesis. While genetic inhibition of TFEB abolishes the cholesterol clearance and exocytosis effect by SFN. In the NPC1 mouse model, SFN dephosphorylates/activates TFEB in brain and exhibits potent efficacy of rescuing the loss of Purkinje cells and body weight. Hence, pharmacological upregulating lysosome machinery via targeting TFEB represents a promising approach to treat NPC and related lysosomal storage diseases, and provides the possibility of TFEB agonists ie SFN as potential NPC therapeutic candidates.

尼曼-皮克C型病（Niemann–Pick disease type C, NPC）是一种毁灭性的溶酶体贮积症，其特征为溶酶体内胆固醇异常蓄积。目前，针对NPC尚无有效治疗手段。转录因子EB（Transcription factor EB, TFEB）属于小眼症转录因子家族（microphthalmia transcription factors, MiTF）成员，现已被证实是溶酶体功能的核心调控因子，可促进细胞内贮积底物的清除。然而，目前尚不清楚TFEB是否在NPC疾病的胆固醇清除过程中发挥作用。本研究证实，相较于MiTF家族另一成员TFE3，转基因过表达TFEB可促进多种NPC1细胞模型中的胆固醇清除。此前本团队鉴定出的天然小分子TFEB激动剂萝卜硫素（sulforaphane, SFN），可通过药理学方式激活TFEB，能够显著改善人源和鼠源NPC1细胞模型中的胆固醇蓄积。在NPC1细胞中，SFN通过依赖于活性氧（ROS）-钙离子（Ca²+）-钙调磷酸酶（calcineurin）、不依赖于MTOR的通路，诱导TFEB的核转位，并上调TFEB下游靶基因的表达，进而促进溶酶体胞吐与溶酶体生物发生。而通过遗传学手段抑制TFEB，则可消除SFN介导的胆固醇清除与胞吐效应。在NPC1小鼠模型中，SFN可在脑组织中使TFEB去磷酸化并激活其功能，并且能够有效挽救浦肯野细胞丢失与体重下降的表型。因此，通过靶向TFEB上调溶酶体功能，是治疗NPC及相关溶酶体贮积症的极具潜力的策略，同时也为以TFEB激动剂（如SFN）作为NPC潜在治疗候选药物提供了可能性。