Furuta Nobumichi, Takeuchi Hiroki, Amano Atsuo
Department of Oral Frontier Biology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita-Osaka 565-0871, Japan.
Infect Immun. 2009 Nov;77(11):4761-70. doi: 10.1128/IAI.00841-09. Epub 2009 Sep 8.
Porphyromonas gingivalis, a periodontal pathogen, secretes outer membrane vesicles (MVs) that contain major virulence factors, including proteases termed gingipains (Arg-gingipain [Rgp] and Lys-gingipain [Kgp]). We recently showed that P. gingivalis MVs swiftly enter host epithelial cells via an endocytosis pathway and are finally sorted to lytic compartments. However, it remains unknown whether MV entry impairs cellular function. Herein, we analyzed cellular functional impairment following entry of P. gingivalis into epithelial cells, including HeLa and immortalized human gingival epithelial (IHGE) cells. After being taken up by endocytic vacuoles, MVs degraded the cellular transferrin receptor (TfR) and integrin-related signaling molecules, such as paxillin and focal adhesion kinase (FAK), which resulted in depletion of intracellular transferrin and inhibition of cellular migration. Few Rgp-null MVs entered the cells, and these negligibly degraded TfR, whereas paxillin and FAK degradation was significant. In contrast, Kgp-null MVs clearly entered the cells and degraded TfR, while they scarcely degraded paxillin and FAK. In addition, both wild-type and Kgp-null MVs significantly impaired cellular migration, whereas the effect of Rgp-null MVs was limited. Our findings suggest that, following entry of P. gingivalis MVs into host cells, MV-associated gingipains degrade cellular functional molecules such as TfR and paxillin/FAK, resulting in cellular impairment, indicating that P. gingivalis MVs are potent vehicles for transmission of virulence factors into host cells and are involved in the etiology of periodontitis.
牙龈卟啉单胞菌是一种牙周病原体，可分泌含有主要毒力因子的外膜囊泡（MVs），这些毒力因子包括被称为牙龈蛋白酶的蛋白酶（精氨酸牙龈蛋白酶[Rgp]和赖氨酸牙龈蛋白酶[Kgp]）。我们最近发现，牙龈卟啉单胞菌MVs通过内吞途径迅速进入宿主上皮细胞，并最终被分选到溶酶体中。然而，MVs的进入是否会损害细胞功能仍不清楚。在此，我们分析了牙龈卟啉单胞菌进入上皮细胞（包括HeLa细胞和永生化人牙龈上皮[IHGE]细胞）后对细胞功能的损害。MVs被内吞液泡摄取后，会降解细胞转铁蛋白受体（TfR）和整合素相关信号分子，如桩蛋白和粘着斑激酶（FAK），从而导致细胞内转铁蛋白耗尽并抑制细胞迁移。几乎没有Rgp缺失的MVs进入细胞，并且它们对TfR的降解可以忽略不计，而桩蛋白和FAK的降解则很明显。相反，Kgp缺失的MVs能明显进入细胞并降解TfR，而它们几乎不降解桩蛋白和FAK。此外，野生型和Kgp缺失的MVs均显著损害细胞迁移，而Rgp缺失的MVs的作用有限。我们的研究结果表明，牙龈卟啉单胞菌MVs进入宿主细胞后与MV相关的牙龈蛋白酶会降解细胞功能分子，如TfR和桩蛋白/FAK，从而导致细胞损伤，这表明牙龈卟啉单胞菌MVs是将毒力因子传递到宿主细胞的有效载体，并参与了牙周炎的发病机制。
