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Porphyromonas gingivalis traffics into endoplasmic reticulum-rich-autophagosomes for successful survival in human gingival epithelial cells.

ABSTRACT: Porphyromonas gingivalis, an opportunistic pathogen usurps gingival epithelial cells (GECs) as primary intracellular niche for its colonization in the oral mucosa. However, the precise characterization of the intracellular trafficking and fate of P. gingivalis in GECs remains incomplete. Therefore, we employed high-resolution three-dimensional-transmission-electron-microscopy to determine the subcellular location of P. gingivalis in human primary GECs upon invasion. Serial sections of infected-GECs and their tomographic reconstruction depicted ER-rich-double-membrane autophagosomal-vacuoles harboring P. gingivalis. Western-blotting and fluorescence confocal microscopy showed that P. gingivalis significantly induces LC3-lipidation in a time-dependent-manner and co-localizes with LC3, ER-lumen-protein Bip, or ER-tracker, which are major components of the phagophore membrane. Furthermore, GECs that were infected with FMN-green-fluorescent transformant-strain (PgFbFP) and selectively permeabilized by digitonin showed rapidly increasing large numbers of double-membrane-vacuolar-P. gingivalis over 24 hours of infection with a low-ratio of cytosolically free-bacteria. Moreover, inhibition of autophagy using 3-methyladenine or ATG5 siRNA significantly reduced the viability of intracellular P. gingivalis in GECs as determined by an antibiotic-protection-assay. Lysosomal marker, LAMP-1, showed a low-degree colocalization with P. gingivalis (?20%). PgFbFP was used to investigate the fate of vacuolar- versus cytosolic-P. gingivalis by their association with ubiquitin-binding-adaptor-proteins, NDP52 and p62. Only cytosolic-P. gingivalis had a significant association with both markers, which suggests cytosolically-free bacteria are likely destined to the lysosomal-degradation pathway whereas the vacuolar-P. gingivalis survives. Therefore, the results reveal a novel mechanism for P. gingivalis survival in GECs by harnessing host autophagy machinery to establish a successful replicative niche and persistence in the oral mucosa.

SUBMITTER: Lee K

PROVIDER: S-EPMC5955440 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Porphyromonas gingivalis traffics into endoplasmic reticulum-rich-autophagosomes for successful survival in human gingival epithelial cells.

Lee Kyulim K Roberts JoAnn S JS Choi Chul Hee CH Atanasova Kalina R KR Yilmaz Özlem Ö

Virulence 20181201 1

Porphyromonas gingivalis, an opportunistic pathogen usurps gingival epithelial cells (GECs) as primary intracellular niche for its colonization in the oral mucosa. However, the precise characterization of the intracellular trafficking and fate of P. gingivalis in GECs remains incomplete. Therefore, we employed high-resolution three-dimensional-transmission-electron-microscopy to determine the subcellular location of P. gingivalis in human primary GECs upon invasion. Serial sections of infected-G ...[more]

PMID: 29616874

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Project description:Porphyromonas gingivalis is a pathogen in severe periodontal disease. Able to exploit an intracellular lifestyle within primary gingival epithelial cells (GECs), a reservoir of P. gingivalis can persist within the gingival epithelia. This process is facilitated by manipulation of the host cell signal transduction cascades which can impact cell cycle, cell death and cytokine responses. Using microarrays, we investigated the ability of P. gingivalis 33277 to regulate microRNA (miRNA) expression in GECs. One of several miRNAs differentially regulated by GECs in the presence of P. gingivalis was miR-203, which was upregulated 4-fold compared with uninfected controls. Differential regulation of miR-203 was confirmed by qRT-PCR. Putative targets of miR-203, suppressors of cytokine signaling (SOCS) 3 and 6, were evaluated by qRT-PCR. SOCS3 and SOCS6 mRNA levels were reduced >5-fold and >2-fold, respectively, in P. gingivalis-infected GECs compared with controls. Silencing miR-203 using a si-RNA construct reversed the inhibition of SOCS3 expression. A dual luciferase assay confirmed binding of miR-203 to the putative target binding site of SOCS3 3’ UTR. Western blot analysis demonstrated that activation of Stat3, a downstream target of SOCS, was diminished following miR-203 silencing. This study shows that induction of miRNAs by P. gingivalis can modulate important host signaling responses. MicroRNAs differentially expressed in human gingival epithelial cells in response to P. gingivalis infection were identified. P. gingivalis were reacted with primary gingival epithelial cells at an MOI of 100 for 6 hours at 37C in 5% CO2. Co-cultures were carried out in triplicate. The GECs were lysed with Trizol (Invitrogen) prior to RNA extraction and total RNA isolation. The microarray assay was performed using a service provider (LC Sciences). The assay started from 4 to 8 µg total RNA sample which was size fractionated using a YM-100 Microcon centrifugal filter (Millipore) and the small RNAs (< 300 nt) isolated were 3’-extended with a poly(A) tail using poly(A) polymerase. An oligonucleotide tag was then ligated to the poly(A) tail for later fluorescent dye staining. Hybridization was performed overnight on a µParaflo microfluidic chip using a micro-circulation pump (Atactic Technologies). The hybridization melting temperatures were balanced by chemical modifications of the detection probes. Hybridization used 100 uL 6xSSPE buffer (0.90 M NaCl, 60 mM Na2HPO4, 6 mM EDTA, pH 6.8) containing 25% formamide at 34 °C. After RNA hybridization, tag-conjugating Cy3 dyes were circulated through the microfluidic chip for dye staining. Fluorescence images were collected using a laser scanner (GenePix 4000B, Molecular Device) and digitized using Array-Pro image analysis software (Media Cybernetics). Microarray data were analyzed by first subtracting the background and then normalizing the signals using a LOWESS filter (Locally-weighted Regression). For a transcript to be listed as detectable it had a signal intensity higher than 3×(background standard deviation) and spot coefficient of variance (CV) < 0.5. CV was calculated by (standard deviation)/(signal intensity). When repeating probes are present on an array, a transcript is listed as detectable only if the signals from at least 50% of the repeating probes are above detection level. t-Test is performed between “control” and “test” sample groups. T-values are calculated for each miRNA, and p-values are computed from the theoretical t-distribution. miRNAs with p-values below a critical p-value (typically 0.01) are selected for cluster analysis. The clustering is done using hierarchical method and is performed with average linkage and Euclidean distance metric. This experiment includes a total of 6 samples which are divided in to 2 groups, each with 3 biological repeats: 3 untreated normal samples as controls and 3 infected samples as the treated condition.

Dataset Information

Porphyromonas gingivalis traffics into endoplasmic reticulum-rich-autophagosomes for successful survival in human gingival epithelial cells.

Publications

Porphyromonas gingivalis traffics into endoplasmic reticulum-rich-autophagosomes for successful survival in human gingival epithelial cells.

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