Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland.
Department of Pathology and Immunology, Division of Immunobiology, Washington University School of Medicine, St. Louis, Missouri, USA.
Mol Oral Microbiol. 2023 Aug;38(4):334-346. doi: 10.1111/omi.12427. Epub 2023 Jun 22.
Porphyromonas gingivalis is an oral pathogen that promotes dysbiosis by quenching the bactericidal activity of the host immune system while maintaining chronic inflammation, leading to periodontitis. This involves the secretion of virulence factors such as P. gingivalis peptidyl arginine deiminase (PPAD), which converts the C-terminal Arg residues of bacterial and host-derived proteins and peptides into citrulline. We have previously shown that PPAD activity and major fimbriae (containing FimA) are necessary for P. gingivalis to activate Toll-like receptor 2 (TLR2). TLR2 is an important component of the innate immune system and plays a predominant role in the recognition of P. gingivalis by host cells. Here, we extend those findings to show that P. gingivalis strains deficient for PPAD and fimbriae induced almost identical transcriptional profiles in infected primary human gingival fibroblasts (PHGFs), but these differed substantially from the transcriptome elicited by the wild-type ATCC 33277 strain. Apparently, PPAD-modified fimbriae trigger the host cell response to P. gingivalis, as confirmed by showing that the proinflammatory host cell response mediated by TLR2 is dependent on PPAD activity and the presence of fimbriae, with type I fimbriae as the most potent TLR2 activators. We also found that PPAD-modified accessory fimbrial subunits (FimC, FimD, and FimE) alone or in combination are TLR2 ligands in a reporter cell line. Although FimA polymerization to form the fimbrial shaft was not required for TLR2 activation, the secretion and proteolytic maturation of FimA were necessary for signaling by accessory Fim proteins. This was supported by showing that the proinflammatory activation of PHGFs is dependent on PPAD and accessory fimbrial subunits. We conclude that accessory fimbrial subunits are modified by PPAD and stimulate the response to P. gingivalis infection in a TLR2-dependent manner.
牙龈卟啉单胞菌是一种口腔病原体，通过抑制宿主免疫系统的杀菌活性并维持慢性炎症来促进失调，从而导致牙周炎。这涉及到毒力因子的分泌，如牙龈卟啉单胞菌肽精氨酸脱亚氨酶（PPAD），它将细菌和宿主来源的蛋白质和肽的 C 末端精氨酸残基转化为瓜氨酸。我们之前已经表明，PPAD 活性和主要菌毛（包含 FimA）对于牙龈卟啉单胞菌激活 Toll 样受体 2（TLR2）是必要的。TLR2 是先天免疫系统的重要组成部分，在宿主细胞识别牙龈卟啉单胞菌方面起着主要作用。在这里，我们扩展了这些发现，表明缺乏 PPAD 和菌毛的牙龈卟啉单胞菌菌株在感染原代人牙龈成纤维细胞（PHGF）时诱导的转录谱几乎相同，但与野生型 ATCC 33277 菌株引起的转录组有很大不同。显然，PPAD 修饰的菌毛触发宿主细胞对牙龈卟啉单胞菌的反应，这一点通过证明 TLR2 介导的促炎宿主细胞反应依赖于 PPAD 活性和菌毛的存在，而 I 型菌毛是最强的 TLR2 激活剂得到证实。我们还发现，PPAD 修饰的辅助菌毛亚基（FimC、FimD 和 FimE）单独或组合在报告细胞系中都是 TLR2 配体。虽然 FimA 聚合形成菌毛轴对于 TLR2 激活不是必需的，但 FimA 的分泌和蛋白水解成熟对于辅助 Fim 蛋白的信号转导是必需的。这一点得到了支持，即 PHGF 的促炎激活依赖于 PPAD 和辅助菌毛亚基。我们得出结论，辅助菌毛亚基被 PPAD 修饰，并以 TLR2 依赖的方式刺激对牙龈卟啉单胞菌感染的反应。
