Al-Khodor Souhaila, Marshall-Batty Kimberly, Nair Vinod, Ding Li, Greenberg David E, Fraser Iain D C
Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
Cell Microbiol. 2014 Mar;16(3):378-95. doi: 10.1111/cmi.12223. Epub 2013 Nov 6.
Selective autophagy functions to specifically degrade cellular cargo tagged by ubiquitination, including bacteria. Strains of the Burkholderia cepacia complex (Bcc) are opportunistic pathogens that cause life-threatening infections in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD). While there is evidence that defective macrophage autophagy in a mouse model of CF can influence B. cenocepacia susceptibility, there have been no comprehensive studies on how this bacterium is sensed and targeted by the host autophagy response in human macrophages. Here, we describe the intracellular life cycle of B. cenocepacia J2315 and its interaction with the autophagy pathway in human cells. Electron and confocal microscopy analyses demonstrate that the invading bacteria interact transiently with the endocytic pathway before escaping to the cytosol. This escape triggers theselective autophagy pathway, and the recruitment of ubiquitin, the ubiquitin-binding adaptors p62 and NDP52 and the autophagosome membrane-associated protein LC3B, to the bacterial vicinity. However, despite recruitment of these key autophagy pathway effectors, B. cenocepacia blocks autophagosome completion and replicates in the host cytosol. We find that a pre-infection increase in cellular autophagy flux can significantly inhibit B. cenocepacia replication and that lower autophagy flux in macrophages from immunocompromised CGD patients could contribute to increased B. cenocepacia susceptibility, identifying autophagy manipulation as a potential therapeutic approach to reduce bacterial burden in B. cenocepacia infections.
选择性自噬的功能是特异性降解由泛素化标记的细胞内物质，包括细菌。洋葱伯克霍尔德菌复合体（Bcc）菌株是机会致病菌，可在囊性纤维化（CF）患者和慢性肉芽肿病（CGD）患者中引发危及生命的感染。虽然有证据表明CF小鼠模型中巨噬细胞自噬缺陷会影响洋葱伯克霍尔德菌的易感性，但尚未有关于人类巨噬细胞中宿主自噬反应如何感知和靶向这种细菌的全面研究。在此，我们描述了洋葱伯克霍尔德菌J2315在细胞内的生命周期及其与人类细胞自噬途径的相互作用。电子显微镜和共聚焦显微镜分析表明，入侵的细菌在逃逸到细胞质之前会与内吞途径短暂相互作用。这种逃逸触发了选择性自噬途径，并使泛素、泛素结合衔接蛋白p62和NDP52以及自噬体膜相关蛋白LC3B募集到细菌附近。然而，尽管募集了这些关键的自噬途径效应物，洋葱伯克霍尔德菌仍会阻止自噬体的形成并在宿主细胞质中复制。我们发现，感染前细胞自噬通量的增加可显著抑制洋葱伯克霍尔德菌的复制，而免疫受损的CGD患者巨噬细胞中较低的自噬通量可能导致洋葱伯克霍尔德菌易感性增加，这表明自噬调控是一种潜在的治疗方法，可减轻洋葱伯克霍尔德菌感染中的细菌负荷。
