Autophagy-independent function of MAP-LC3 during intracellular propagation of Chlamydia trachomatis
Autophagy-independent function of MAP-LC3 during intracellular propagation of Chlamydia trachomatis
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DOI：
10.4161/auto.7.8.15597
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发表时间：
2011-08-01
期刊：
影响因子：
13.3
通讯作者：
Meyer, Thomas F.
中科院分区：
文献类型：
--
作者：
Al-Younes, Hesham M.;Al-Zeer, Munir A.;Meyer, Thomas F.
微管相关蛋白1（MAP 1）轻链3（LC 3）已被证明是一个有用的自噬体标记物在病原体和宿主自噬机制之间的相互作用的研究。然而，已知LC 3的功能超出其在自噬体形成中的作用。我们以前报道，内在LC 3与细胞内沙眼衣原体包涵体在人类上皮细胞。在这里，我们表明，LC 3，最有可能的细胞质非脂化形式，与C。沙眼包涵体作为微管相关蛋白而不是自噬体相关组分。相比之下，N-末端GFP标记的LC 3专门靶向自噬体而不是衣原体包涵体。免疫荧光分析显示，早在感染后18 h，LC 3和MAP 1亚基A和B就与包涵体相关。包涵体结合的LC 3与微管网络相连。微管结构的解聚破坏了LC 3/MAP 1与包涵体的结合。此外，siRNA介导的MAP 1和LC 3蛋白的沉默揭示了它们在C.沙眼有趣的是，有缺陷的自噬显著增强了衣原体的生长，表明自噬机制对细菌发育的抑制作用。然而，自噬缺陷细胞中LC 3的耗竭显著降低了衣原体的繁殖。因此，我们的研究结果证明了LC 3在细胞内细菌发病机制中不同于自噬的新功能。
Microtubule-associated protein 1 (MAP1) light chain 3 (LC3) has proven useful as an autophagosomal marker in studies on the interaction between pathogens and the host autophagic machinery. However, the function of LC3 is known to extend above and beyond its role in autophagosome formation. We previously reported that intrinsic LC3 is associated with the intracellular Chlamydia trachomatis inclusion in human epithelial cells. Here we show that LC3, most likely the cytoplasmic nonlipidated form, interacts with the C. trachomatis inclusion as a microtubule-associated protein rather than an autophagosome-associated component. In contrast, N-terminally GFP-tagged LC3 exclusively targets autophagosomes rather than chlamydial inclusions. Immunofluorescence analysis revealed an association of LC3 and MAP1 subunits A and B with the inclusion as early as 18 h post-infection. Inclusion-bound LC3 was connected with the microtubular network. Depolymerization of the microtubular architecture disrupted the association of LC3/MAP1s with the inclusion. Furthermore, siRNA-mediated silencing of the MAP1 and LC3 proteins revealed their essential function in the intracellular growth of C. trachomatis. Interestingly, defective autophagy remarkably enhanced chlamydial growth, suggesting a suppressive effect of the autophagic machinery on bacterial development. However, depletion of LC3 in autophagy-deficient cells noticeably reduced chlamydial propagation. Thus, our findings demonstrate a new function for LC3, distinct from autophagy, in intracellular bacterial pathogenesis.