Activation of NF-ΚB by Toxoplasma gondii correlates with increased expression of antiapoptotic genes and localization of phosphorylated IΚB to the parasitophorous vacuole membrane

Robert E. Molestina, T. Matthew Payne, Isabelle Coppens, Anthony P. Sinai

Research output: Contribution to journalArticle

Abstract

Mammalian cells infected with Toxoplasma gondii are resistant to apoptosis induced by a variety of stimuli. We have demonstrated that the host transcription factor NF-κB plays a pivotal role in the T.-gondii-mediated blockade of apoptosis because inhibition is lost in cells lacking the p65 (RelA) subunit of NF-κB (p65-/-). In the present study, we examined the effects of T. gondii infection on NF-κB activation and the expression of genes involved in the apoptotic cascade. Infection of wild-type mouse embryonic fibroblasts (MEFs) with T.-gondii-induced nuclear translocation of the p50 and p65 subunits of NF-κB as examined by immunoblotting of nuclear extracts, immunofluorescence and electrophoretic mobility shift assays. A comparison of apoptotic gene expression profiles from wild-type and p65-/- MEFs revealed distinct patterns of induction in response to T. gondii infection. In particular, the differences seen in the Bcl-2 and IAP families are consistent with the antiapoptotic responses observed in the resistant wild-type cells compared with the sensitive p65-/- fibroblasts. Consistent with NF-κB activation, T. gondii infection promoted phosphorylation of the inhibitor IκB. Interestingly, phosphorylated IκB was concentrated on the parasitophorous vacuole membrane (PVM), suggesting a parasite-directed event. Results from this study suggest that activation of NF-κB plays an important role in stimulation of antiapoptotic gene expression by T. gondii. Furthermore, recruitment of phosphorylated IκB to the PVM implies the presence of intrinsic factor(s) in T. gondii that might be used to manipulate the NF-κB signaling pathway in the host to elicit a survival response during infection.

Original languageEnglish (US)
Pages (from-to)4359-4371
Number of pages13
JournalJournal of Cell Science
Volume116
Issue number21
DOIs
StatePublished - Nov 1 2003
Externally publishedYes

Fingerprint

Toxoplasmosis
Toxoplasma
Vacuoles
Fibroblasts
Gene Expression
Membranes
Apoptosis
Intrinsic Factor
Electrophoretic Mobility Shift Assay
Infection
Transcriptome
Immunoblotting
Transcriptional Activation
Fluorescent Antibody Technique
Parasites
Transcription Factors
Phosphorylation

Keywords

  • Apoptosis
  • Bc12
  • IΚB
  • IAP
  • NF-ΚB
  • Toxoplasma gondii

ASJC Scopus subject areas

  • Cell Biology

Cite this

Activation of NF-ΚB by Toxoplasma gondii correlates with increased expression of antiapoptotic genes and localization of phosphorylated IΚB to the parasitophorous vacuole membrane. / Molestina, Robert E.; Payne, T. Matthew; Coppens, Isabelle; Sinai, Anthony P.

In: Journal of Cell Science, Vol. 116, No. 21, 01.11.2003, p. 4359-4371.

Research output: Contribution to journalArticle

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abstract = "Mammalian cells infected with Toxoplasma gondii are resistant to apoptosis induced by a variety of stimuli. We have demonstrated that the host transcription factor NF-κB plays a pivotal role in the T.-gondii-mediated blockade of apoptosis because inhibition is lost in cells lacking the p65 (RelA) subunit of NF-κB (p65-/-). In the present study, we examined the effects of T. gondii infection on NF-κB activation and the expression of genes involved in the apoptotic cascade. Infection of wild-type mouse embryonic fibroblasts (MEFs) with T.-gondii-induced nuclear translocation of the p50 and p65 subunits of NF-κB as examined by immunoblotting of nuclear extracts, immunofluorescence and electrophoretic mobility shift assays. A comparison of apoptotic gene expression profiles from wild-type and p65-/- MEFs revealed distinct patterns of induction in response to T. gondii infection. In particular, the differences seen in the Bcl-2 and IAP families are consistent with the antiapoptotic responses observed in the resistant wild-type cells compared with the sensitive p65-/- fibroblasts. Consistent with NF-κB activation, T. gondii infection promoted phosphorylation of the inhibitor IκB. Interestingly, phosphorylated IκB was concentrated on the parasitophorous vacuole membrane (PVM), suggesting a parasite-directed event. Results from this study suggest that activation of NF-κB plays an important role in stimulation of antiapoptotic gene expression by T. gondii. Furthermore, recruitment of phosphorylated IκB to the PVM implies the presence of intrinsic factor(s) in T. gondii that might be used to manipulate the NF-κB signaling pathway in the host to elicit a survival response during infection.",
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