title: Autophagy exacerbates caspase-dependent apoptotic cell death after short times of starvation.
abstract: Autophagy is generally regarded as a mechanism to promote cell survival. However, autophagy can occasionally be the mechanism responsible of cell demise. We have found that a concomitant depletion of glucose, nutrients and growth factors provoked cell death in a variety of cell lines. This death process was contingent upon caspase activation and was mediated by BAX/BAK proteins, thus indicating its apoptotic nature and the engagement of an intrinsic pathway. In order to abrogate autophagy, 3-methyladenine (3-MA), BECLIN-1 siRNA and Atg5 knock-out (Tet-Off type) approaches were alternatively employed. Irrespective of the procedure, at short times of starvation, we found that the ongoing autophagy was sensitizing cells to the permeabilization of the mitochondrial outer membrane (MOMP), caspase activation and, therefore, apoptosis. On the contrary, at longer times of starvation, autophagy displayed its characteristic pro-survival effect on cells. As far as we know, we provide the first experimental paradigm where time is the only variable determining the final outcome of autophagy. In other words, we have circumscribed in time the shift transforming autophagy from a cell death to a protection mechanism. Moreover, at short times, starvation-driven autophagy exacerbated the apoptotic cell death caused by several antitumor agents. In agreement with this fact, their apoptotic effects were greatly diminished by autophagy inhibition. The implications of these facts in tumor biology will be discussed.
authors.affiliation: Cell Death Regulation by Non-coding RNAs (ncRNAs) Group, Departament de Medicina Experimental, Universitat de Lleida/IRBLleida, Av. Rovira Roure 80, E-25198 Lleida, Spain; Pharmacology Unit, Departament de Medicina Experimental, Universitat de Lleida/IRBLleida, Av. Rovira Roure 80, E-25198 Lleida, Spain.
authors.forename: Paolo
authors.initials: P
authors.lastname: Mattiolo
authors.affiliation: Cell Death, Senescence and Survival Group, Departament de Bioquímica i Biologia Molecular & Institut de Neurociències, Facultat de Medicina, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain.
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Yuste
authors.affiliation: Pharmacology Unit, Departament de Medicina Experimental, Universitat de Lleida/IRBLleida, Av. Rovira Roure 80, E-25198 Lleida, Spain.
authors.forename: Jacint
authors.initials: J
authors.lastname: Boix
authors.affiliation: Cell Death Regulation by Non-coding RNAs (ncRNAs) Group, Departament de Medicina Experimental, Universitat de Lleida/IRBLleida, Av. Rovira Roure 80, E-25198 Lleida, Spain; Pharmacology Unit, Departament de Medicina Experimental, Universitat de Lleida/IRBLleida, Av. Rovira Roure 80, E-25198 Lleida, Spain. Electronic address: judit.ribas@mex.udl.cat.
authors.forename: Judit
authors.initials: J
authors.lastname: Ribas
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001343:Autophagy / Q000502:physiology*; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D018345:Mice, Knockout; D013997:Time Factors
chemical_list: D020169:Caspases
keywords: 2-Phenylethynesulfonamide (Pubmed CID 327653); 3-Methyladenine (Pubmed CID 1673); 7-Bromoindirubin-3-oxime (Pubmed CID 11846148); Apoptosis; Autophagy; Camptothecin (Pubmed CID 24360); Caspases; Etoposide (Pubmed CID 36462); Mitochondrial permeabilization; Necrostatin-1 (Pubmed CID 282833); Q-VD-OPh (Pubmed CID 11237609); Short-term starvation; Staurosporine (Pubmed CID 44259)