a Department of Microbiology and Immunology , University of Melbourne at the Peter Doherty Institute for Infection and Immunity , Melbourne , Victoria , Australia.
Autophagy. 2018;14(10):1710-1725. doi: 10.1080/15548627.2018.1483806. Epub 2018 Jul 29.
Coxiella burnetii is an intracellular bacterial pathogen which causes Q fever, a human infection with the ability to cause chronic disease with potentially life-threatening outcomes. In humans, Coxiella infects alveolar macrophages where it replicates to high numbers in a unique, pathogen-directed lysosome-derived vacuole. This compartment, termed the Coxiella-containing vacuole (CCV), has a low internal pH and contains markers both of lysosomes and autophagosomes. The CCV membrane is also enriched with CLTC (clathrin heavy chain) and this contributes to the success of the CCV. Here, we describe a role for CLTC, a scaffolding protein of clathrin-coated vesicles, in facilitating the fusion of autophagosomes with the CCV. During gene silencing of CLTC, CCVs are unable to fuse with each other, a phenotype also seen when silencing genes involved in macroautophagy/autophagy. MAP1LC3B/LC3B, which is normally observed inside the CCV, is excluded from CCVs in the absence of CLTC. Additionally, this study demonstrates that autophagosome fusion contributes to CCV size as cell starvation and subsequent autophagy induction leads to further CCV expansion. This is CLTC dependent, as the absence of CLTC renders autophagosomes no longer able to contribute to the expansion of the CCV. This investigation provides a functional link between CLTC and autophagy in the context of Coxiella infection and highlights the CCV as an important tool to explore the interactions between these vesicular trafficking pathways.
贝氏考克斯体是一种细胞内细菌病原体，可引起 Q 热，这是一种人类感染，有导致慢性疾病的能力，并有潜在的致命后果。在人类中，考克斯体感染肺泡巨噬细胞，在那里它在一个独特的、病原体定向的溶酶体衍生的空泡中大量复制。这个隔间被称为考克斯体包含的空泡（CCV），其内部 pH 值较低，并且包含溶酶体和自噬体的标志物。CCV 膜还富含 CLTC（网格蛋白重链），这有助于 CCV 的成功。在这里，我们描述了 CLTC 的作用，CLTC 是网格蛋白包被小泡的支架蛋白，它促进了自噬体与 CCV 的融合。在 CLTC 基因沉默期间，CCV 无法彼此融合，这种表型在沉默参与巨自噬/自噬的基因时也可见。MAP1LC3B/LC3B，通常在 CCV 内观察到，在没有 CLTC 的情况下从 CCV 中排除。此外，这项研究表明自噬体融合有助于 CCV 的大小，因为细胞饥饿和随后的自噬诱导导致 CCV 的进一步扩张。这是 CLTC 依赖的，因为缺乏 CLTC 使自噬体不再能够为 CCV 的扩张做出贡献。这项研究在考克斯体感染的背景下提供了 CLTC 和自噬之间的功能联系，并强调了 CCV 是探索这些囊泡运输途径之间相互作用的重要工具。
