Ehrlichia Activation of Wnt-PI3K-mTOR Signaling Inhibits Autolysosome Generation and Autophagic Destruction by the Mononuclear Phagocyte
Ehrlichia Activation of Wnt-PI3K-mTOR Signaling Inhibits Autolysosome Generation and Autophagic Destruction by the Mononuclear Phagocyte
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DOI：
10.1128/iai.00690-17
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发表时间：
2017-12-01
影响因子：
3.1
通讯作者：
McBride, Jere W.
中科院分区：
文献类型：
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作者：
Lina, Taslima T.;Luo, Tian;McBride, Jere W.
在多细胞生物中，自噬被诱导为一种先天防御机制。值得注意的是，专性细胞内细菌查菲埃里希体存在于早期的内体样空泡中，并通过未知的机制绕过溶酶体融合，从而避免自噬溶酶体的破坏。在这份报告中，我们揭示了Wnt信号在抑制埃立克体的溶酶体融合和自体溶酶体破坏中起着至关重要的作用。在早期感染期间，自噬体与埃里希体空泡融合以形成两性体，这通过自噬标记物如LC 3（微管相关蛋白1轻链3）、Beclin-1和p62的存在来指示。LC 3共定位与埃立克体桑椹胚感染后的第1，2和3天，并增加LC 3 II水平在感染过程中检测到，达到最高水平的第3天。埃里希体空泡没有与溶酶体标志物LAMP 2共定位，并且溶酶体在感染细胞中重新分布并且水平显著降低。Wnt受体信号传导组分Dishevelled特异性抑制剂诱导溶酶体与对应于p62降解的埃里希体包涵体融合，并促进转录因子EB（TFEB）核定位。E. Chaffeensis感染激活了磷脂酰肌醇3-激酶（PI 3 K）-Akt-mTOR（雷帕霉素的机械靶标）途径，并且激活由三种埃里希体串联重复蛋白（TRP）效应物诱导，其中TRP 120诱导最强的激活。此外，使用Wnt抑制剂和PI 3 K-GSK 3-mTOR信号传导的关键组分的小干扰RNA（siRNA）敲低进行的糖原合成酶激酶-3（GSK 3）的诱导降低了埃里希体存活。这份报告揭示了埃里希体利用进化上保守的Wnt途径来抑制自体溶酶体的产生，从而导致逃避这一重要的先天免疫防御机制。
In multicellular organisms, autophagy is induced as an innate defense mechanism. Notably, the obligate intracellular bacterium Ehrlichia chaffeensis resides in early endosome-like vacuoles and circumvents lysosomal fusion through an unknown mechanism, thereby avoiding destruction in the autophagolysosome. In this report, we reveal that Wnt signaling plays a crucial role in inhibition of lysosomal fusion and autolysosomal destruction of ehrlichiae. During early infection, autophagosomes fuse with ehrlichial vacuoles to form an amphisome indicated by the presence of autophagy markers such as LC3 (microtubule-associated protein 1 light chain 3), Beclin-1, and p62. LC3 colocalized with ehrlichial morulae on days 1, 2, and 3 postinfection, and increased LC3II levels were detected during infection, reaching a maximal level on day 3. Ehrlichial vacuoles did not colocalize with the lysosomal marker LAMP2, and lysosomes were redistributed and dramatically reduced in level in the infected cells. An inhibitor specific for the Wnt receptor signaling component Dishevelled induced lysosomal fusion with ehrlichial inclusions corresponding to p62 degradation and promoted transcription factor EB (TFEB) nuclear localization. E. chaffeensis infection activated the phosphatidylinositol 3-kinase (PI3K)-Akt-mTOR (mechanistic target of rapamycin) pathway, and activation was induced by three ehrlichial tandem repeat protein (TRP) effectors, with TRP120 inducing the strongest activation. Moreover, induction of glycogen synthase kinase-3 (GSK3) performed using a Wnt inhibitor and small interfering RNA (siRNA) knockdown of critical components of PI3K-GSK3-mTOR signaling decreased ehrlichial survival. This report reveals Ehrlichia exploitation of the evolutionarily conserved Wnt pathway to inhibit autolysosome generation, thereby leading to evasion of this important innate immune defense mechanism.