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Association of mitogen-activated protein kinase pathways with gingival epithelial cell responses to Porphyromonas
K Watanabe1, O Yilmaz, S F Nakhjiri
1Department of Oral Biology, University of Washington, Seattle, Washington 98195, USA.
Abstract:
Mitogen-activated protein (MAP) kinase pathways are key factors in host signaling events and can also play important roles in the internalization of pathogenic bacteria by host cells. Porphyromonas gingivalis, a periodontal pathogen, can efficiently invade human gingival epithelial cells (GECs). In this study, we examined the activation of MAP kinase pathways in GECs infected with P. gingivalis. c-Jun N-terminal kinase (JNK) was activated after 5 min of infection with P. gingivalis, whereas noninvasive Streptococcus gordonii did not have a significant effect on JNK activation. In contrast, extracellular signal-regulated kinase (ERK) 1/2 was downregulated in a dose-dependent manner by P. gingivalis, but not by S. gordonii, after a 15-min exposure. Nonmetabolically active P. gingivalis cells were unable to modulate MAP kinase activity. U0126, a specific inhibitor of MEK1/2 (ERK1/2 kinase), and toxin B, a specific inhibitor of Rho family GTPases, had no effect on P. gingivalis invasion. Genistein, a tyrosine protein kinase inhibitor, blocked uptake of P. gingivalis. The transcriptional regulator NF-kappaB was not activated by P. gingivalis. These results suggest that P. gingivalis can selectively target components of the MAP kinase pathways. ERK1/2, while not involved in P. gingivalis invasion of GECs, may be downregulated by internalized P. gingivalis. Activation of JNK is associated with the invasive process of P. gingivalis.
Insights
Porphyromonas gingivalis selectively activates c-Jun N-terminal kinase (JNK) during invasion of human gingival epithelial cells. Extracellular signal-regulated kinase (ERK) 1/2 is downregulated, but not essential for this bacterial entry process.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Mitogen-activated protein (MAP) kinase pathways regulate host cell signaling and bacterial invasion.
- Porphyromonas gingivalis is a periodontal pathogen known to invade human gingival epithelial cells (GECs).
Purpose of the Study:
- To investigate the role of MAP kinase pathways in P. gingivalis invasion of GECs.
- To determine which specific MAP kinase pathways are modulated during this interaction.
Main Methods:
- Infection of GECs with P. gingivalis and Streptococcus gordonii.
- Analysis of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) 1/2 activation.
- Use of specific inhibitors (U0126, Toxin B, Genistein) and nonmetabolically active bacteria.
Main Results:
- P. gingivalis rapidly activated JNK, while S. gordonii did not.
- P. gingivalis dose-dependently downregulated ERK1/2.
- Tyrosine protein kinase inhibition blocked P. gingivalis invasion; MEK1/2 and Rho GTPase inhibition did not.
- NF-kappaB was not activated.
Conclusions:
- P. gingivalis selectively targets MAP kinase pathways during host cell invasion.
- JNK activation is linked to the invasive process.
- ERK1/2 downregulation occurs post-internalization and is not critical for invasion.