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. 2002 Jan;70(1):55-61.
doi: 10.1128/IAI.70.1.55-61.2002.

Role of Bcl-2 family members in caspase-independent apoptosis during Chlamydia infection

Jean-Luc Perfettini  1 , John C Reed, Nicole Israël, Jean-Claude Martinou, Alice Dautry-Varsat, David M Ojcius
Affiliations

Role of Bcl-2 family members in caspase-independent apoptosis during Chlamydia infection

Jean-Luc Perfettini et al. Infect Immun. 2002 Jan.

Abstract

Infection with an obligate intracellular bacterium, the Chlamydia trachomatis lymphogranuloma venereum (LGV/L2) strain or the guinea pig inclusion conjunctivitis serovar of Chlamydia psittaci, leads to apoptosis of host cells. The apoptosis is not affected by a broad-spectrum caspase inhibitor, and caspase-3 is not activated in infected cells, suggesting that apoptosis mediated by these two strains of Chlamydia is independent of known caspases. Overexpression of the proapoptotic Bcl-2 family member, Bax, was previously shown to induce caspase-independent apoptosis, and we find that Bax is activated and translocates from the cytosol to the mitochondria in C. psittaci-infected cells. C. psittaci-induced apoptosis is inhibited in host cells overexpressing Bax inhibitor-1 and is inhibited through overexpression of Bcl-2, which blocks both caspase-dependent and -independent apoptosis. As Bax and mitochondria are ideally located to sense stress-related metabolic changes emanating from the interior of an infected cell, it is likely that Bax-dependent apoptosis may also be observed in cells infected with other intracellular pathogens.

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Figures

FIG. 1.
FIG. 1.
Caspase-independent cell death during infection of epithelial cells or monocytes with the GPIC strain of C. psittaci or the LGV/L2 strain of C. trachomatis. HeLa (A) and U937 (B) were infected with C. psittaci, at an MOI of 0.7 and 1.0, respectively, or with C. trachomatis at an MOI of 0.3, for 48 h in the presence or absence of 100 μM z-VAD-fmk. As positive controls for caspase-dependent cell death, HeLa cells were incubated with 15 μM TPEN for 17 h, and U937 cells were incubated with anti-Fas antibody (0.5 μg/ml) for 16 h. Apoptosis was measured by cytofluorimetry as described in Materials and Methods. The values represent the means and standard deviations (error bars) of three separate experiments. (C) Caspase-3 activity was measured in lysates from HeLa cells infected with C. psittaci for 48 h or treated with TPEN for 17 h, using the fluorescent substrate for caspase-3, DEVD-AFC, as described in Materials and Methods. The same level of apoptosis was measured in TPEN-treated or Chlamydia-infected cells under these conditions. The extent of DEVD-AFC cleavage in TPEN-treated cells was defined as 100, and the other values were normalized with respect to this positive control. The values represent the means and standard deviations (error bars) of three samples treated with TPEN or infected with Chlamydia on separate days.
FIG. 2.
FIG. 2.
Bax activation during infection with Chlamydia. (A) Bax activation was measured in HeLa cells by cytofluorimetry with the anti-Bax antibody (N-20). The dotted line represents the spectrum in the absence of N-20 antibody, the solid line corresponds to Bax staining in uninfected cells incubated with N-20 and FITC-conjugated second antibody, and filled spectrum shows Bax staining in cells infected for 48 h and incubated with N-20 and second antibody. Bax activation and intracellular distribution were also evaluated by confocal microscopy. Nuclei stained with Hoechst of uninfected HeLa cells (B) or cells infected with C. psittaci for 48 h (C), showing fragmenting nuclei in infected cells, are shown. The arrowhead indicates a Chlamydia inclusion. Subcellular localization of Bax (F) and mitochondria (D) in uninfected cells is shown. Subcellular localization of Bax (G) and mitochondria (E) in cells undergoing apoptosis in infected sample is also shown.
FIG. 3.
FIG. 3.
Inhibition of Chlamydia-induced apoptosis in cells overexpressing Bax inhibitor-1 (BI-1) or Bcl-2. (A) HeLa cells were transfected transiently with constructs encoding BI-1 or Bcl-2 for 1 day and then infected with C. psittaci for 48 h. Apoptosis was measured by immunofluorescence, as described in Materials and Methods, and the level of apoptosis was normalized to 100 for untransfected cells. (B) The stable U937 or HeLa clones overexpressing Bcl-2 and the corresponding clones transfected with control expression vector were infected with C. psittaci for 48 h. Apoptosis was measured by cytofluorimetry, and the level of apoptosis was normalized to 100 for untransfected cells. Each series of experiments was performed at least three times.
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References

    1. Adams, J. M., and S. Cory. 1998. The Bcl-2 protein family: arbiters of cell survival. Science 281: 1322–1326. - PubMed
    1. Aillet, F., H. Masutani, C. Elbim, H. Raoul, L. Chêne, M.-T. Nugeyre, C. Paya, F. Barré-Sinoussi, M.-A. Gougerot-Pocidalo, and N. Israël. 1998. Human immunodeficiency virus induces a dual regulation of Bcl-2, resulting in persistent infection of CD4+ T or monocytic cell lines. J. Virol. 72: 9698–9705. - PMC - PubMed
    1. Amarante-Mendes, G. P., D. M. Finucane, S. J. Martin, T. G. Cotter, G. S. Salvesen, and D. R. Green. 1998. Anti-apoptotic oncogenes prevent caspase-dependent and independent commitment for cell death. Cell Death Differ. 5: 298–306. - PubMed
    1. Ameisen, J. C., J. Estaquier, and T. Idziorek. 1994. From AIDS to parasite infection: pathogen-mediated subversion of programmed cell death as a mechanism for immune dysregulation. Immunol. Rev. 142: 9–51. - PubMed
    1. Banks, J., B. Eddie, J. Schachter, and K. F. Meyer. 1970. Plaque formation by Chlamydia in L cells. Infect. Immun. 1: 259–262. - PMC - PubMed

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