Acetylation of apurinic/apyrimidinic endonuclease-1 regulates Helicobacter pylori-mediated gastric epithelial cell apoptosis.
OBJECTIVE
Helicobacter pylori-induced gastric epithelial cell (GEC) apoptosis is a complex process that includes activation of the tumor suppressor p53. p53-mediated apoptosis involves p53 activation, bax transcription, and cytochrome c release from mitochondria. Apurinic/apyrimidinic endonuclease-1 (APE-1) regulates transcriptional activity of p53, and H pylori induce APE-1 expression in human GECs. H pylori infection increases intracellular calcium ion concentration [Ca2+]i of GECs, which induces APE-1 acetylation. We investigated the effects of H pylori infection and APE-1 acetylation on GEC apoptosis.


METHODS
AGS cells (wild-type or with suppressed APE-1), KATO III cells, and cells isolated from gastric biopsy specimens were infected with H pylori. Effects were examined by immunoblotting, real-time reverse-transcription polymerase chain reaction, immunoprecipitation, immunofluorescence microscopy, chromatin immunoprecipitation, mobility shift, DNA binding, and luciferase assays.


RESULTS
H pylori infection increased [Ca2+]i and acetylation of APE-1 in GECs, but the acetylation status of APE-1 did not affect the transcriptional activity of p53. In GECs, expression of a form of APE-1 that could not be acetylated increased total and mitochondrial levels of Bax and induced release of cytochrome c and fragmentation of DNA; expression of wild-type APE-1 reduced these apoptotic events. We identified a negative calcium response element in the human bax promoter and found that poly (adenosine diphosphate-ribose) polymerase 1 recruited the acetylated APE-1/histone deacetylase-1 repressor complex to bax nCaRE.


CONCLUSIONS
H pylori-mediated acetylation of APE-1 suppresses Bax expression; this prevents p53-mediated apoptosis when H pylori infect GECs.
Bhattacharyya
Asima
A
Department of Medicine, University of Virginia, Charlottesville, Virginia 22908-0708, USA.
Chattopadhyay
Ranajoy
R
Burnette
Brent R
BR
Cross
Janet V
JV
Mitra
Sankar
S
Ernst
Peter B
PB
Bhakat
Kishor K
KK
Crowe
Sheila E
SE
D000107:Acetylation; D017209:Apoptosis / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000382:microbiology / Q000473:pathology*; D005753:Gastric Mucosa / Q000166:cytology* / Q000382:microbiology / Q000473:pathology; D016481:Helicobacter Infections / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016480:Helicobacter pylori / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D016159:Tumor Suppressor Protein p53; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D002118:Calcium