Heat-shock protein 70 antagonizes apoptosis-inducing factor.
Heat-shock protein 70 (Hsp70) has been reported to block apoptosis by binding apoptosis protease activating factor-1 (Apaf-1), thereby preventing constitution of the apoptosome, the Apaf-1/cytochrome c/caspase-9 activation complex [1,2]. Here we show that overexpression of Hsp70 protects Apaf-1-/- cells against death induced by serum withdrawal, indicating that Apaf-1 is not the only target of the anti-apoptotic action of Hsp70. We investigated the effect of Hsp70 on apoptosis mediated by the caspase-independent death effector apoptosis inducing factor (AIF), which is a mitochondrial intermembrane flavoprotein [3,4]. In a cell-free system, Hsp70 prevented the AIF-induced chromatin condensation of purified nuclei. Hsp70 specifically interacted with AIF, as shown by ligand blots and co-immunoprecipitation. Cells overexpressing Hsp70 were protected against the apoptogenic effects of AIF targeted to the extramitochondrial compartment. In contrast, an anti-sense Hsp70 complementary DNA, which reduced the expression of endogenous Hsp70, increased sensitivity to the lethal effect of AIF. The ATP-binding domain of Hsp70 seemed to be dispensable for inhibiting cell death induced by serum withdrawal, AIF binding and AIF inhibition, although it was required for Apaf-1 binding. Together, our data indicate that Hsp70 can inhibit apoptosis by interfering with target proteins other than Apaf-1, one of which is AIF.
Ravagnan
L
L
CNRS UMR 1599, Institute Gustave Roussy, Pavillon de Recherche 1, 39 rue Camille Desmoulins, 94805 Villejuif, France.
Gurbuxani
S
S
Susin
S A
SA
Maisse
C
C
Daugas
E
E
Zamzami
N
N
Mak
T
T
Jäättelä
M
M
Penninger
J M
JM
Garrido
C
C
Kroemer
G
G
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051033:Apoptosis Inducing Factor; D053477:Apoptotic Protease-Activating Factor 1; D002467:Cell Nucleus / Q000648:ultrastructure; D002470:Cell Survival; D002478:Cells, Cultured; D002843:Chromatin / Q000502:physiology / Q000648:ultrastructure; D016895:Culture Media, Serum-Free; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology*; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
C506593:Apaf1 protein, mouse; D051033:Apoptosis Inducing Factor; D053477:Apoptotic Protease-Activating Factor 1; D002843:Chromatin; D016895:Culture Media, Serum-Free; D005420:Flavoproteins; D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; C494830:AIFM1 protein, mouse; D011506:Proteins; D011994:Recombinant Proteins