Schäfer Walter, Eckart Rita A, Schmid Benedikt, Cagköylü Hasret, Hof Kerstin, Muller Yves A, Amin Bushra, Lührmann Anja
Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Universitätsklinikum Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Wasserturmstrasse 3-5, D-91054, Erlangen, Germany.
Lehrstuhl für Biotechnik, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestrasse 91, D-91052, Erlangen, Germany.
Cell Microbiol. 2017 Jan;19(1). doi: 10.1111/cmi.12634. Epub 2016 Jul 15.
The obligate intracellular bacterium Coxiella burnetii causes the zoonotic disease Q-fever. Coxiella pathogenesis depends on a functional type IV secretion system (T4SS). The T4SS effector AnkG inhibits pathogen-induced host cell apoptosis, which is believed to be important for the establishment of a persistent infection. However, the mode of action of AnkG is not fully understood. We have previously demonstrated that binding of AnkG to p32 is crucial for migration of AnkG into the nucleus and that nuclear localization of AnkG is essential for its anti-apoptotic activity. Here, we compared the activity of AnkG from the C. burnetii strains Nine Mile and Dugway. Although there is only a single amino acid exchange at residue 11, we observed a difference in anti-apoptotic activity and nuclear migration. Mutation of amino acid 11 to glutamic acid, threonine or valine results in AnkG mutants that had lost the anti-apoptotic activity and the ability to migrate into the nucleus. We identified Importin-α1 to bind to AnkG, but not to the mutants and concluded that binding of AnkG to p32 and Importin-α1 is essential for migration into the nucleus. Also during Coxiella infection binding of AnkG to p32 and Importin-α1 is crucial for nuclear localization of AnkG.
专性胞内细菌伯氏考克斯体可引发人畜共患病Q热。考克斯体的致病机制依赖于功能性IV型分泌系统（T4SS）。T4SS效应蛋白AnkG可抑制病原体诱导的宿主细胞凋亡，据信这对于建立持续性感染至关重要。然而，AnkG的作用方式尚未完全明确。我们之前已证明，AnkG与p32的结合对于AnkG迁移至细胞核至关重要，且AnkG的核定位对其抗凋亡活性必不可少。在此，我们比较了来自伯氏考克斯体Nine Mile和Dugway菌株的AnkG的活性。尽管在第11位残基处仅有一个氨基酸替换，但我们观察到抗凋亡活性和核迁移存在差异。将第11位氨基酸突变为谷氨酸、苏氨酸或缬氨酸会导致AnkG突变体丧失抗凋亡活性及迁移至细胞核的能力。我们鉴定出输入蛋白α1可与AnkG结合，但不能与突变体结合，并得出结论，AnkG与p32及输入蛋白α1的结合对于迁移至细胞核至关重要。在考克斯体感染期间，AnkG与p32及输入蛋白α1的结合对于AnkG的核定位也至关重要。
