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Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation
08:47

Lighting Up the Pathways to Caspase Activation Using Bimolecular Fluorescence Complementation

Published on: March 5, 2018

HSP27 inhibits cytochrome c-dependent activation of procaspase-9

C Garrido1, J M Bruey, A Fromentin

  • 1INSERM U517, Groupe Biologie et Thérapie des Cancers (JE 515), Faculty of Medicine and Pharmacy, 21033 Dijon, France. cgarrido@u-bourgogne.fr

FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology
|November 2, 1999
PubMed

Insights

Small heat shock protein HSP27 prevents programmed cell death (apoptosis) in human leukemic cells. HSP27 inhibits caspase-9 activation, a key step in the apoptotic pathway, making cells less sensitive to chemotherapy drugs like etoposide.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Small heat shock protein HSP27 has been shown to inhibit apoptotic pathways in mammalian cells.
  • Understanding the mechanisms by which HSP27 modulates apoptosis is crucial for developing novel therapeutic strategies.

Purpose of the Study:

  • To investigate the role of HSP27 in etoposide-induced apoptosis in U937 human leukemic cells.
  • To elucidate the specific molecular mechanisms by which HSP27 confers resistance to apoptosis.

Main Methods:

  • Overexpression of HSP27 in U937 cells.
  • Assessment of etoposide-induced cytotoxicity and apoptosis.
  • Analysis of poly(ADP-ribose)polymerase cleavage and procaspase-3 activation.
  • Measurement of cytochrome c release from mitochondria.
  • Cell-free assays to study caspase activation in response to cytochrome c and dATP.
  • Immunodepletion techniques to assess the role of HSP27 in caspase activation.

Main Results:

  • HSP27 overexpression decreased U937 cell sensitivity to etoposide-induced cytotoxicity by preventing apoptosis.
  • HSP27 delayed poly(ADP-ribose)polymerase cleavage and procaspase-3 activation, similar to Bcl-2.
  • Unlike Bcl-2, HSP27 did not prevent etoposide-induced cytochrome c release.
  • In cell-free systems, HSP27 inhibited cytochrome c/dATP-mediated activation of procaspase-3 and procaspase-9.
  • Immunodepletion of HSP27 restored caspase activation in cell-free extracts.

Conclusions:

  • HSP27 inhibits etoposide-induced apoptosis by preventing the activation of caspase-9, downstream of cytochrome c release.
  • HSP27 acts as a critical inhibitor of the intrinsic apoptotic pathway at the level of caspase-9 activation.

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