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

Abstract

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.

Mitochondrial dysfunction is involved in the aggravation of periodontitis by diabetes

“…MtDNA mutation has also been proved to increase the susceptibility of human cells to apoptosis (Rommelaere et al. ). Therefore, we cannot completely rule out the possibility that mtDNA mutation contributes to the enhanced periodontium cells apoptosis in DP.…”

Crosstalk between mitochondrial (dys)function and mitochondrial abundance

“…However, an excessive mitochondrial mass induced by mitochondrial dysfunction may also have deleterious effects, as it has been shown that apoptosis markers are associated with ragged red fibers, as evidenced in a large-scale analysis conducted in individual muscle fibers from patients suffering from different mitochondrial myopathies (Aure et al, 2006). The question to know whether these apoptotic markers occur spontaneously in response to mitochondrial dysfunction or results from a higher sensitivity to pro-apoptotic molecules present in the cell environment and challenging cells that display mitochondrial dysfunction is not completely resolved as some evidence that mtDNA mutation and depletion increase resistance of human cells to apoptosis (Park et al, 2004) while we, and others, have shown that cells lacking mtDNA or harboring point mutations are more sensitive to pro-apoptotic molecules (Liu et al, 2004;Rommelaere et al, 2011). Cell type, stimuli and nature of the mitochondrial dysfunction might explain these differences in cell behavior.…”

High levels of Cellular Prion Protein improve astrocyte development

“…The data presented here provide evidence that PrP C over‐expression promotes resistance to cell death, as well as early astrocyte maturation. In this study, we demonstrated that PrP C over‐expression protects astrocytes from cell death induced by staurosporine, an alkaloid isolated from the bacterium Streptomyces staurosporeus , which is known to induce apoptosis in many cell lines through caspase‐3 activation [37–40].…”

“…These results are in accordance to previous data [5] and indicate the involvement of the PKA pathway in the protection against saurosporin‐induced astrocyte death promoted by STI1 interaction with PrP C . Staurosporin treatment is known to increase expression of pro‐apoptotic oncogene Bax and reduce Bcl‐2 expression [37–40]. However, it is unknown whether these pathways are also affected by STI1.…”