Caspase-independent apoptosis in Friend’ s erythroleukemia cells: role of mitochondrial ATP synthesis impairment in relocation of apoptosis-inducing factor and endonuclease G Marina Comelli & Nadia Genero & Irene Mavelli Received: 4 August 2008 / Accepted: 9 January 2009 / Published online: 29 January 2009 # Springer Science + Business Media, LLC 2009 Abstract Mitochondria have emerged as the central components of both caspase-dependent and indepen- dent apoptosis signalling pathways through release of different apoptogenic proteins. We previously docu- mented that parental and differentiated Friend’s eryth- roleukemia cells were induced to apoptosis by oligomycin and H 2 O 2 exposure, showing that the energy impairment occurring in both cases as a consequence of a severe mitochondrial F 0 F 1 ATPsynthase inactivation was a common early feature. Here we provide evidence for AIF and Endo G mitochondrio-nuclear relocation in both cases, as a component of caspase-independent apoptosis pathways. No detectable change in mitochondrial trans- membrane potential and no variation in mitochondrial levels of Bcl-2 and Bax are observed. These results point to the osmotic rupture of the mitochondrial outer membrane as occurring in response to cell exposure to the two energy-impairing treatments under conditions preserving the mitochondrial inner membrane. A critical role of the mitochondrial F 0 F 1 ATP synthase inhibition in this process is also suggested. Keywords Mitochondrial F 0 F 1 ATPsynthase . Friend’ s erythroleukemia cells . Apoptosis . Apoptosis inducing factor . Endonuclease G . H 2 O 2 . Oligomycin . Energy impairment . Mitochondrial outer membrane permeabilization Abbreviations AIF apoptosis inducing factor BSA bovine serum albumin CS citrate synthase CsA cyclosporine A D-FELC differentiated FELC Δψ m mitochondrial transmembrane potential Endo G endonuclease G FELC Friend’ s erythroleukemia cells HMBA N,N′-hexamethylene bisacetamide IAPs inhibitor of apoptosis proteins IMP intermembrane space JC-1 5,5′,6,6′-tetrachloro-1,1′,3,3′- tetraethylbenzimidazolcarbocyanine iodide LDH lactate dehydrogenase MIM mitochondrial inner membrane MOM mitochondrial outer membrane P-FELC parental FELC PBS phosphate-buffered saline PMSF phenylmethanesulfonyl fluoride PTP permeability transition pore ROS reactive oxygen species SDS sodium dodecyl sulfate z-VAD-fmk Z-Val-Ala-DL-Asp(Ome)- fluoromethylketone J Bioenerg Biomembr (2009) 41:49–59 DOI 10.1007/s10863-009-9196-8 M. Comelli : N. Genero : I. Mavelli Department of Biomedical Sciences and Technologies, University of Udine, 33100 Udine, Italy M. Comelli : I. Mavelli M.A.T.I. Centre of Excellence, University of Udine, 33100 Udine, Italy M. Comelli (*) Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, Piazzale Kolbe 4, 33100 Udine, Italy e-mail: marina.comelli@uniud.it