Division of Pharmacology and Toxicology, College of Pharmacy; Institute for Cellular and Molecular Biology; and Institute for Neuroscience, The University of Texas at Austin, Austin, TX, USA.
Center for Innovative Drug Discovery, Department of Chemistry, University of Texas San Antonio, San Antonio, TX, USA.
Life Sci Alliance. 2019 Jun 26;2(3). doi: 10.26508/lsa.201900439. Print 2019 Jun.
Shiga toxin 1 (STx1) and 2 (STx2), produced by Shiga toxin-producing , cause lethal untreatable disease. The toxins invade cells via retrograde trafficking. Direct early endosome-to-Golgi transport allows the toxins to evade degradative late endosomes. Blocking toxin trafficking, particularly at the early endosome-to-Golgi step, is appealing, but transport mechanisms of the more disease-relevant STx2 are unclear. Using data from a genome-wide siRNA screen, we discovered that disruption of the fusion of late endosomes, but not autophagosomes, with lysosomes blocked the early endosome-to-Golgi transport of STx2. A subsequent screen of clinically approved lysosome-targeting drugs identified tamoxifen (TAM) to be a potent inhibitor of the trafficking and toxicity of STx1 and STx2 in cells. The protective effect was independent of estrogen receptors but dependent on the weak base property of TAM, which allowed TAM to increase endolysosomal pH and alter endosomal dynamics. Importantly, TAM treatment enhanced survival of mice injected with a lethal dose of STx1 or STx2. Thus, it may be possible to repurpose TAM for treating Shiga toxin-producing infections.
志贺毒素 1（STx1）和 2（STx2）由产志贺毒素的细菌产生，会导致致命的无法治疗的疾病。这些毒素通过逆行运输进入细胞。直接的早期内体到高尔基体运输允许毒素逃避降解性晚期内体。阻断毒素运输，特别是在早期内体到高尔基体的步骤，是很有吸引力的，但与更相关疾病的 STx2 的运输机制尚不清楚。利用来自全基因组 siRNA 筛选的数据，我们发现，破坏晚期内体与溶酶体的融合，而不是自噬体与溶酶体的融合，阻断了 STx2 的早期内体到高尔基体的运输。随后对临床批准的溶酶体靶向药物进行筛选，发现他莫昔芬（TAM）是一种有效的抑制剂，可抑制细胞中 STx1 和 STx2 的转运和毒性。这种保护作用不依赖于雌激素受体，但依赖于 TAM 的弱碱性特性，这使得 TAM 能够增加内溶酶体 pH 值并改变内体动力学。重要的是，TAM 治疗增强了注射致死剂量 STx1 或 STx2 的小鼠的存活率。因此，他莫昔芬可能被重新用于治疗产志贺毒素的细菌感染。
