Characterization of Mannheimia (Pasteurella) haemolytica leukotoxin interaction with bovine alveolar macrophage β2 integrins
Characterization of Mannheimia (Pasteurella) haemolytica leukotoxin interaction with bovine alveolar macrophage β2 integrins
复制标题
DOI：
10.1051/vetres:2005036
复制
发表时间：
2005-09-01
影响因子：
4.4
通讯作者：
Maheswaran, SK
中科院分区：
文献类型：
--
作者：
Thumbikat, P;Dileepan, T;Maheswaran, SK
溶血性曼氏杆菌（巴氏杆菌）是牛肺炎性曼氏病的病原体，可产生一种外毒性白细胞毒素。白细胞毒素（LktA）是细菌溶细胞素RTX（毒素中的重复序列）家族的成员，与其他毒素的区别在于其通过与特定受体结合而对反刍动物白细胞产生的独特靶细胞特异性。我们先前已经证明β 2整合素LFA-1是牛白细胞中LktA的受体，并参与白细胞毒素诱导的生物学效应。然而，LFA-1中参与与LktA结合的亚基以及导致细胞活化的结合后信号传导尚未得到很好的表征。我们研究的目的是确定这些精确的亚基对牛肺泡巨噬细胞和表征它们与LktA的相互作用。本研究的结果表明，尽管LktA可以有效地结合LFA-1和Mac-1的CD 18亚基，但仅通过LFA-1观察到结合后信号传导事件，包括细胞内钙离子升高和CD 18尾磷酸化。此外，LktA还结合LFA-1的CD 11 a亚基。LktA与CD 11 a的结合可被I（插入）结构域（CD 11 a上的主要配体结合界面）的小分子抑制剂抑制。I结构域抑制显著减弱LktA诱导的细胞内钙升高和CD 18尾的酪氨酸磷酸化。根据我们的研究结果，我们认为，LFA-1作为白细胞毒素受体的牛肺泡巨噬细胞的功能。
Mannheimia (Pasteurella) haemolytica, the etiologic agent of bovine pneumonic mannheimiosis, produces an exotoxic leukotoxin. The leukotoxin (LktA) is a member of the RTX ( repeats in toxin) family of bacterial cytolysins and is distinguished from other toxins by its unique target cell specificity to ruminant leukocytes occurring through binding to a specific receptor. We have demonstrated previously that the beta(2) integrin LFA-1 is a receptor for LktA in bovine leukocytes and is involved in leukotoxin-induced biological effects. However the subunits within LFA-1 involved in binding to LktA, and post-binding signaling leading to cellular activation have not been well characterized. The purpose of our study was to pinpoint these precise subunits on bovine alveolar macrophages and to characterize their interaction with LktA. The results in this study indicate that although LktA can efficiently bind to the CD18 subunit of both LFA-1 and Mac-1, post-binding signaling events including elevation of intracellular calcium and CD18 tail phosphorylation are only observed through LFA-1. Furthermore, LktA also binds to the CD11a subunit of LFA-1. LktA binding to CD11a could be inhibited by a small molecule inhibitor of the I( inserted)-domain, the major ligand binding interface on CD11a. I-domain inhibition significantly blunts LktA-induced intracellular calcium elevation and tyrosine phosphorylation of the CD18 tail. Based on our results we suggest that LFA-1 serves as the functional leukotoxin receptor on bovine alveolar macrophages.