Mannheimia haemolytica leukotoxin induces apoptosis of bovine lymphoblastoid cells (BL-3) via a caspase-9-dependent mitochondrial pathway
Mannheimia haemolytica leukotoxin induces apoptosis of bovine lymphoblastoid cells (BL-3) via a caspase-9-dependent mitochondrial pathway
复制标题
DOI：
10.1128/iai.73.9.5504-5513.2005
复制
发表时间：
2005-09-01
影响因子：
3.1
通讯作者：
Czuprynski, CJ
中科院分区：
文献类型：
--
作者：
Atapattu, DN;Czuprynski, CJ
溶血曼海姆氏菌是牛呼吸道疾病复合体的关键病原体。它产生白细胞毒素 (LKT)，这是一种重要的毒力因子，可导致牛白细胞死亡。 LKT 与 β(2) 整合素 CD11a/CD18 结合，通常会激活促进细胞存活的信号通路。在这项研究中，我们研究了 LKT 诱导牛类淋巴母细胞 (BL-3) 死亡的机制。将 BL-3 细胞与低浓度 LKT 一起孵育会导致 caspase-3 和 caspase-9 激活，但不会激活 caspase-8。同样，促凋亡蛋白 Bax 和 BAD 显着升高，而抗凋亡蛋白 Bcl-2、Bcl(XL) 和 Akt-1 则下调。暴露于 LKT 后，我们还观察到线粒体细胞色素 c 减少，胞质细胞色素 c 相应升高，表明从线粒体区室易位到胞质溶胶。与这一观察结果一致，四甲基罗丹明乙酯高氯酸盐染色显示线粒体膜电位显着降低。这些数据表明 LKT 通过 caspase-9 依赖性线粒体途径诱导 BL-3 细胞凋亡。此外，LKT 处理的 BL-3 细胞线粒体的扫描电子显微照片显示，线粒体外膜存在损伤，这些损伤比之前报道的细胞色素 c 通常释放的通透性转换孔要大。
Mannheimia haemolytica is a key pathogen in the bovine respiratory disease complex. It produces a leukotoxin (LKT) that is an important virulence factor, causing cell death in bovine leukocytes. The LKT binds to the beta(2) integrin CD11a/CD18, which usually activates signaling pathways that facilitate cell survival. In this study, we investigated mechanisms by which LKT induces death in bovine lymphoblastoid cells (BL-3). Incubation of BL-3 cells with a low concentration of LKT results in the activation of caspase-3 and caspase-9 but not caspase-8. Similarly, the proapoptotic proteins Bax and BAD were significantly elevated, while the antiapoptotic proteins Bcl-2, Bcl(XL) and Akt-1 were downregulated. Following exposure to LKT, we also observed a reduction in mitochondrial cytochrome c and corresponding elevation of cytosolic cytochrome c, suggesting translocation from the mitochondrial compartment to the cytosol. Consistent with this observation, tetramethylrhodamine ethyl ester perchlorate staining revealed that mitochondrial membrane potential was significantly reduced. These data suggest that LKT induces apoptosis of BL-3 cells via a caspase-9-dependent mitochondrial pathway. Furthermore, scanning electron micrographs of mitochondria from LKT-treated BL-3 cells revealed lesions in the outer mitochondrial membrane, which are larger than previous reports of the permeability transition pore through which cytochrome c is usually released.