Aggregatibacter actinomycetemcomitans outer membrane protein 29 (Omp29) induces TGF-β-regulated apoptosis signal in human gingival epithelial cells via fibronectin/integrinβ1/FAK cascade.
Gingival junctional epithelial cell apoptosis caused by periodontopathic bacteria exacerbates periodontitis. This pathological apoptosis is involved in the activation of transforming growth factor β (TGF-β). However, the molecular mechanisms by which microbes induce the activation of TGF-β remain unclear. We previously reported that Aggregatibacter actinomycetemcomitans (Aa) activated TGF-β receptor (TGF-βR)/smad2 signalling to induce epithelial cell apoptosis, even though Aa cannot bind to TGF-βR. Additionally, outer membrane protein 29 kDa (Omp29), a member of the Aa Omps family, can induce actin rearrangements via focal adhesion kinase (FAK) signalling, which also plays a role in the activation of TGF-β by cooperating with integrin. Accordingly, we hypothesized that Omp29-induced actin rearrangements via FAK activity would enhance the activation of TGF-β, leading to gingival epithelial cell apoptosis in vitro. By using human gingival epithelial cell line OBA9, we found that Omp29 activated TGF-βR/smad2 signalling and decreased active TGF-β protein levels in the extracellular matrix (ECM) of cell culture, suggesting the transactivation of TGF-βR. Inhibition of actin rearrangements by cytochalasin D or blebbistatin and knockdown of FAK or integrinβ1 expression by siRNA transfection attenuated TGF-βR/smad2 signalling activity and reduction of TGF-β levels in the ECM caused by Omp29. Furthermore, Omp29 bound to fibronectin (Fn) to induce its aggregation on integrinβ1, which is associated with TGF-β signalling activity. All the chemical inhibitors and siRNAs tested blocked Omp29-induced OBA9 cells apoptosis. These results suggest that Omp29 binds to Fn in order to facilitate Fn/integrinβ1/FAK signalling-dependent TGF-β release from the ECM, thereby inducing gingival epithelial cell apoptosis via TGF-βR/smad2 pathway.
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Tetsuya
T
Yoshimoto
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Tsuyoshi
T
Fujita
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Mikihito
M
Kajiya
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Kazuhisa
K
Ouhara
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Shinji
S
Matsuda
Department of Oral Microbiology, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
Hitoshi
H
Komatsuzawa
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Hideki
H
Shiba
Department of Periodontal Medicine, Division of Applied Life Sciences, Institute of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan.
Hidemi
H
Kurihara
D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics* / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D002461:Cell Line, Transformed; D015638:Cytochalasin D / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D005353:Fibronectins / Q000235:genetics* / Q000378:metabolism; D051417:Focal Adhesion Kinase 1 / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D005881:Gingiva / Q000378:metabolism / Q000382:microbiology; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D054884:Host-Pathogen Interactions; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction; D051899:Smad2 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D005353:Fibronectins; D006576:Heterocyclic Compounds, 4 or More Rings; D019012:Integrin beta1; C117494:Omp29 protein, Actinobacillus actinomycetemcomitans; D034741:RNA, Small Interfering; D018125:Receptors, Transforming Growth Factor beta; D011994:Recombinant Proteins; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D016212:Transforming Growth Factor beta; C472645:blebbistatin; D015638:Cytochalasin D; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I