ATP scavenging by the intracellular pathogen Porphyromonas gingivalis inhibits P2X7-mediated host-cell apoptosis.
The purinergic receptor P2X(7) is involved in cell death, inhibition of intracellular infection and secretion of inflammatory cytokines. The role of the P2X(7) receptor in bacterial infection has been primarily established in macrophages. Here we show that primary gingival epithelial cells, an important component of the oral innate immune response, also express functional P2X(7) and are sensitive to ATP-induced apoptosis. Porphyromonas gingivalis, an intracellular bacterium and successful colonizer of oral tissues, can inhibit gingival epithelial cell apoptosis induced by ATP ligation of P2X(7) receptors. A P. gingivalis homologue of nucleoside diphosphate kinase (NDK), an ATP-consuming enzyme, is secreted extracellularly and is required for maximal suppression of apoptosis. An ndk-deficient mutant was unable to prevent ATP-induced host-cell death nor plasma membrane permeabilization in the epithelial cells. Treatment with purified recombinant NDK inhibited ATP-mediated host-cell plasma membrane permeabilization in a dose-dependent manner. Therefore, NDK promotes survival of host cells by hydrolysing extracellular ATP and preventing apoptosis-mediated through P2X(7).
Yilmaz
Ozlem
O
Department of Periodontology, University of Florida, Gainesville, FL 32610, USA. oyilmaz@dental.ufl.edu
Yao
Luyu
L
Maeda
Kazuhiko
K
Rose
Timothy M
TM
Lewis
Emma L
EL
Duman
Memed
M
Lamont
Richard J
RJ
Ojcius
David M
DM
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001426:Bacterial Proteins / Q000378:metabolism; D002478:Cells, Cultured; D005434:Flow Cytometry; D005881:Gingiva / Q000166:cytology / Q000187:drug effects / Q000382:microbiology; D006801:Humans; D020287:In Situ Nick-End Labeling; D008856:Microscopy, Fluorescence; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism; D016966:Porphyromonas gingivalis / Q000378:metabolism / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7
D001426:Bacterial Proteins; C546468:P2RX7 protein, human; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D009701:Nucleoside-Diphosphate Kinase