Liu Jie, Zuo Zehua, Ewing Michael, Cao Qing, Cao Liu, Li Qi, Finkel Toren, Leppla Stephen H, Liu Shihui
Aging Institute of University of Pittsburgh and University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
Division of Cardiology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Nat Microbiol. 2025 May;10(5):1145-1155. doi: 10.1038/s41564-025-01977-x. Epub 2025 Mar 28.
Lethal toxin (LT), the major virulence factor of Bacillus anthracis, proteolytically inactivates MEKs and disables downstream ERK, p38 and JNK pathway signalling leading to tissue damage and mortality. Therapies for LT-induced damage after host cell internalization of the toxin are lacking. Here we constructed MEK variants in which the LT proteolytic site was modified: MEK2(P10V/A11D), MEK3(I27D) and MEK6(I15D). These variants were resistant to proteolysis by LT. Expression in cells enabled sustained activation of ERK and p38 pathways and promoted cell survival upon LT treatment. Survival of LT- or B. anthracis-challenged MEK variant transgenic mice also increased compared with controls. We found that LT-mediated disruption of both ERK and p38 pathway is essential for anthrax pathogenesis. We show that engagement of upstream receptor tyrosine kinases reactivated the LT-disrupted ERK pathway, as did administering a cocktail of EGF, GM-CSF and FGF2 growth factors, which significantly increased survival of LT- or B. anthracis-challenged mice. These findings offer potential towards developing damage-limiting therapeutic strategies for anthrax.
致死毒素（LT）是炭疽芽孢杆菌的主要毒力因子，它通过蛋白水解作用使丝裂原活化蛋白激酶（MEK）失活，并破坏下游的细胞外信号调节激酶（ERK）、p38和c-Jun氨基末端激酶（JNK）信号通路，从而导致组织损伤和死亡。目前缺乏针对毒素内化进入宿主细胞后所引发的LT诱导损伤的治疗方法。在此，我们构建了对LT蛋白水解位点进行修饰的MEK变体：MEK2（P10V/A11D）、MEK3（I27D）和MEK6（I15D）。这些变体对LT的蛋白水解具有抗性。在细胞中表达能够使ERK和p38信号通路持续激活，并在LT处理后促进细胞存活。与对照相比，经LT或炭疽芽孢杆菌攻击的MEK变体转基因小鼠的存活率也有所提高。我们发现，LT介导的ERK和p38信号通路的破坏对于炭疽病发病机制至关重要。我们表明，上游受体酪氨酸激酶的激活可重新激活被LT破坏的ERK信号通路，给予表皮生长因子（EGF）、粒细胞-巨噬细胞集落刺激因子（GM-CSF）和碱性成纤维细胞生长因子2（FGF2）生长因子的混合物也能达到同样效果，这显著提高了经LT或炭疽芽孢杆菌攻击的小鼠的存活率。这些发现为开发限制炭疽病损伤的治疗策略提供了潜力。
