Hypersensitivity of mtDNA-depleted cells to staurosporine-induced apoptosis: roles of Bcl-2 downregulation and cathepsin B

• Published in: American Journal of Physiology: Cell Physiology 2011-05, Vol.300 (5), p.C1090-C1106
• Main Authors: Rommelaere, Guillaume, Michel, Sébastien, Mercy, Ludovic, Fattaccioli, Antoine, Demazy, Catherine, Ninane, Noelle, Houbion, Andrée, Renard, Patricia, Arnould, Thierry
• Format: Article
• Language: English
• Subjects: Apoptosis; Apoptosis - genetics; bcl-X Protein - metabolism; Caspase 3 - metabolism; Cathepsin B - antagonists & inhibitors; Cathepsin B - metabolism; Cell Line, Tumor; Cells; Cytochromes c - metabolism; Dipeptides - pharmacology; DNA Fragmentation; DNA, Mitochondrial - genetics; Down-Regulation; Enzyme Inhibitors - pharmacology; Humans; Lymphoma; Mitochondrial DNA; Myeloid Cell Leukemia Sequence 1 Protein; Permeability; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases - metabolism; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Staurosporine - pharmacology
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00037.2010

We show that mitochondrial DNA (mtDNA)-depleted 143B cells are hypersensitive to staurosporine-induced cell death as evidenced by a more pronounced DNA fragmentation, a stronger activation of caspase-3, an enhanced poly(ADP-ribose) polymerase-1 (PARP-1) cleavage, and a more dramatic cytosolic release of cytochrome c. We also show that B-cell CLL/lymphoma-2 (Bcl-2), B-cell lymphoma extra large (Bcl-X(L)), and myeloid cell leukemia-1 (Mcl-1) are constitutively less abundant in mtDNA-depleted cells, that the inhibition of Bcl-2 and Bcl-X(L) can sensitize the parental cell line to staurosporine-induced apoptosis, and that overexpression of Bcl-2 or Bcl-X(L) can prevent the activation of caspase-3 in ρ(0)143B cells treated with staurosporine. Moreover, the inactivation of cathepsin B with CA074-Me significantly reduced cytochrome c release, caspase-3 activation, PARP-1 cleavage, and DNA fragmentation in mtDNA-depleted cells, whereas the pan-caspase inhibitor failed to completely prevent PARP-1 cleavage and DNA fragmentation in these cells, suggesting that caspase-independent mechanisms are responsible for cell death even if caspases are activated. Finally, we show that cathepsin B is released in the cytosol of ρ(0) cells in response to staurosporine, suggesting that the absence of mitochondrial activity leads to a facilitated permeabilization of lysosomal membranes in response to staurosporine.