Department of Molecular Biology, Umeå University , Umeå, Sweden.
The Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University , Umeå, Sweden.
mBio. 2023 Aug 31;14(4):e0319022. doi: 10.1128/mbio.03190-22. Epub 2023 Aug 2.
The obligate intracellular bacterium inserts a family of inclusion membrane (Inc) proteins into the membrane of its vacuole (the inclusion). The Inc CpoS is a critical suppressor of host cellular immune surveillance, but the underlying mechanism remained elusive. By complementing a mutant with various natural orthologs and variants of CpoS, we linked distinct molecular interactions of CpoS to distinct functions. Unexpectedly, we found CpoS to be essential for the formation of inclusion membrane microdomains that control the spatial organization of multiple Incs involved in signaling and modulation of the host cellular cytoskeleton. While the function of CpoS in microdomains was uncoupled from its role in the suppression of host cellular defenses, we found the ability of CpoS to interact with Rab GTPases to be required not only for the manipulation of membrane trafficking, such as to mediate transport of ceramide-derived lipids (sphingolipids) to the inclusion, but also for the inhibition of Stimulator of interferon genes (STING)-dependent type I interferon responses. Indeed, depletion of Rab35 phenocopied the exacerbated interferon responses observed during infection with CpoS-deficient mutants. Overall, our findings highlight the role of Inc-Inc interactions in shaping the inclusion microenvironment and the modulation of membrane trafficking as a pathogenic immune evasion strategy. IMPORTANCE is a prevalent bacterial pathogen that causes blinding ocular scarring and urogenital infections that can lead to infertility and pregnancy complications. Because can only grow within its host cell, boosting the intrinsic defenses of human cells may represent a novel strategy to fight pathogen replication and survival. Hence, CpoS, a protein known to block host cellular defenses, or processes regulated by CpoS, could provide new opportunities for therapeutic intervention. By revealing CpoS as a multifunctional virulence factor and by linking its ability to block host cellular immune signaling to the modulation of membrane trafficking, the present work may provide a foundation for such rationale targeting and advances our understanding of how intracellular bacteria can shape and protect their growth niche.
专性细胞内细菌将一系列包含膜（Inc）蛋白插入其空泡的膜中（包含物）。Inc CpoS 是宿主细胞免疫监视的关键抑制剂，但潜在的机制仍难以捉摸。通过用各种天然同源物和 CpoS 的变体来补充突变体，我们将 CpoS 的不同分子相互作用与不同的功能联系起来。出乎意料的是，我们发现 CpoS 对于包含膜微域的形成是必不可少的，该微域控制着参与信号转导和宿主细胞细胞骨架调节的多种 Inc 的空间组织。虽然 CpoS 在微域中的功能与其在抑制宿主细胞防御中的作用分离，但我们发现 CpoS 与 Rab GTPases 相互作用的能力不仅需要操纵膜运输，例如介导神经酰胺衍生脂质（鞘脂）向包含物的运输，还需要抑制干扰素基因刺激物（STING）依赖性 I 型干扰素反应。事实上，Rab35 的耗竭模拟了在缺乏 CpoS 的突变体感染过程中观察到的干扰素反应加剧。总的来说，我们的研究结果强调了 Inc-Inc 相互作用在塑造包含物微环境和调节膜运输作为一种致病免疫逃避策略中的作用。 是一种普遍存在的细菌病原体，可导致眼部失明性瘢痕和泌尿生殖系统感染，可导致不孕和妊娠并发症。由于 只能在其宿主细胞内生长，因此增强人体细胞的固有防御能力可能代表一种新的策略来对抗病原体的复制和存活。因此，CpoS，一种已知可阻断宿主细胞防御的 蛋白，或由 CpoS 调节的过程，可能为治疗干预提供新的机会。通过揭示 CpoS 作为一种多功能毒力因子，并将其阻断宿主细胞免疫信号的能力与调节膜运输联系起来，本工作可能为这种基于原理的靶向提供基础，并增进我们对细胞内细菌如何塑造和保护其生长生态位的理解。
