Cathepsin D triggers Bax activation, resulting in selective apoptosis-inducing factor (AIF) relocation in T lymphocytes entering the early commitment phase to apoptosis.
Activated human T lymphocytes exposed to apoptotic stimuli targeting mitochondria (i.e. staurosporine), enter an early, caspase-independent phase of commitment to apoptosis characterized by cell shrinkage and peripheral chromatin condensation. We show that during this phase, AIF is selectively released from the intermembrane space of mitochondria, and that Bax undergo conformational change, relocation to mitochondria, and insertion into the outer mitochondrial membrane, in a Bid-independent manner. We analyzed the subcellular distribution of cathepsins (Cat) B, D, and L, in a search for caspase-independent factors responsible for Bax activation and AIF release. All were translocated from lysosomes to the cytosol, in correlation with limited destabilization of the lysosomes and release of lysosomal molecules in a size selective manner. However, only inhibition of Cat D activity by pepstatin A inhibited the early apoptotic events and delayed cell death, even in the presence of bafilomycin A1, an inhibitor of vacuolar type H+-ATPase, which inhibits acidification in lysosomes. Small interfering RNA-mediated gene silencing was used to inactivate Cat D, Bax, and AIF gene expression. This allowed us to define a novel sequence of events in which Cat D triggers Bax activation, Bax induces the selective release of mitochondrial AIF, and the latter is responsible for the early apoptotic phenotype.
Bidère
Nicolas
N
Laboratoire de Greffes d'Epithéliums et Régulation de l'Activation Lymphocytaire, Unité INSERM 542, Hôpital Paul Brousse, Villejuif, France.
Lorenzo
Hans K
HK
Carmona
Sylvie
S
Laforge
Mireille
M
Harper
Francis
F
Dumont
Céline
C
Senik
Anna
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051033:Apoptosis Inducing Factor; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002402:Cathepsin D / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes / Q000201:enzymology; D018942:Macrolides; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology; D010436:Pepstatins / Q000494:pharmacology; D010641:Phenotype; D011480:Protease Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology; D051028:bcl-2-Associated X Protein
C494829:AIFM1 protein, human; D000900:Anti-Bacterial Agents; D051033:Apoptosis Inducing Factor; C494826:BAX protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D005420:Flavoproteins; D018942:Macrolides; D008565:Membrane Proteins; D010436:Pepstatins; D011480:Protease Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; C040929:bafilomycin A1; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L; D002402:Cathepsin D; D019311:Staurosporine; C031375:pepstatin