Hsp27 functions as a negative regulator of cytochrome c-dependent activation of procaspase-3.
The release of mitochondrial cytochrome c by genotoxic stress induces the formation of a cytosolic complex with Apaf-1 (mammalian CED4 homolog) and thereby the activation of procaspase-3 (cas-3) and procaspase-9 (cas-9). Here we demonstrate that heat-shock protein 27 (Hsp27) inhibits cytochrome c (cyt c)-dependent activation of cas-3. Hsp27 had no effect on cyt c release, Apaf-1 and cas-9 activation. By contrast, our results show that Hsp27 associates with cas-3, but not Apaf-1 or cas-9, and inhibits activation of cas-3 by cas-9-mediated proteolysis. Furthermore, the present results demonstrate that immunodepletion of Hsp27 depletes cas-3. Importantly, treatment of cells with DNA damaging agents dissociates the Hsp27/cas-3 complex and relieves inhibition of cas-3 activation. These findings define a novel function for Hsp27 and provide the first evidence that a heat shock protein represses cas-3 activation.
Pandey
P
P
Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Farber
R
R
Nakazawa
A
A
Kumar
S
S
Bharti
A
A
Nalin
C
C
Weichselbaum
R
R
Kufe
D
D
Kharbanda
S
S
D000199:Actins / Q000378:metabolism; D053477:Apoptotic Protease-Activating Factor 1; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D002460:Cell Line / Q000187:drug effects / Q000528:radiation effects; D002474:Cell-Free System; D003561:Cytarabine / Q000494:pharmacology; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000528:radiation effects; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes / Q000378:metabolism; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009842:Oligopeptides / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D051745:Protein Kinase C-delta; D011506:Proteins / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology
C506592:APAF1 protein, human; D000199:Actins; D053477:Apoptotic Protease-Activating Factor 1; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D006360:Heat-Shock Proteins; D007527:Isoenzymes; D009842:Oligopeptides; D011506:Proteins; D003561:Cytarabine; D008741:Methyl Methanesulfonate; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D019311:Staurosporine