TY - JOUR
T1 - PK11195, a ligand of the mitochondrial benzodiazepine receptor, facilitates the induction of apoptosis and reverses Bcl-2-mediated cytoprotection
AU - Hirsch, Tamara
AU - Decaudin, Didier
AU - Susin, Santos A.
AU - Marchetti, Philippe
AU - Larochette, Nathanael
AU - Resche-Rigon, Michèle
AU - Kroemer, Guido
N1 - Funding Information:
This work has been supported by grants from ANRS, ARC, CNRS, FRM, INSERM, LFC, and Hoechst-Marion-Roussel (to G.K.). We thank Dr. Pierre Carayon (Sanofi-Elf, Montpellier, France) for helpful suggestions.
PY - 1998/6/15
Y1 - 1998/6/15
N2 - One critical step of the apoptotic process is the opening of the mitochondrial permeability transition (PT) pore leading to the disruption of mitochondrial membrane integrity and to the dissipation of the inner transmembrane proton gradient (ΔΨ(m)). The mitochondrial PT pore is a polyprotein structure which is inhibited by the apoptosis-inhibitory oncoprotein Bcl-2 and which is closely associated with the mitochondrial benzodiazepine receptor (mBzR). Here we show that PK11195, a prototypic ligand of the 18-kDa mBzR, facilitates the induction of ΔΨ(m) disruption and subsequent apoptosis by a number of different agents, including agonists of the glucocorticoid receptor, chemotherapeutic agents (etoposide, doxorubicin), gamma irradiation, and the proapoptotic second messenger ceramide. Whereas PK11195 itself has no cytotoxic effect, it enhances apoptosis induction by these agents. This effect is not observed for benzodiazepine diazepam, whose binding site in the mBzR differs from PK11195. PK11195 partially reverses Bcl-2 mediated inhibition of apoptosis in two different cell lines. Thus, transfection-enforced Bcl-2 overexpression confers protection against glucocorticoids and chemotherapeutic agents, and this protection is largely reversed by the addition of PK11195. This effect is observed at the level of ΔΨ(m) dissipation as well as at the level of nuclear apoptosis. To gain insights into the site of action of PK11195, we performed experiments on isolated organelles. PK11195 reverses the Bcl-2- mediated mitochondrial retention of apoptogenic factors which cause isolated nuclei to undergo apoptosis in a cell-free system. Mitochondria from control cells, but not mitochondria from Bcl-2-overexpressing cells, readily release such apoptogenic factors in response to atractyloside, a ligand of the adenine nucleotide translocator. However, control and Bcl-2-overexpressing mitochondria respond equally well to a combination of atractyloside and PK11195. Altogether, these findings indicate that PK11195 abolishes apoptosis inhibition by Bcl-2 via a direct effect on mitochondria. Moreover, they suggest a novel strategy for enhancing the susceptibility of cells to apoptosis induction and, concomitantly, for reversing Bcl-2-mediated cytoprotection.
AB - One critical step of the apoptotic process is the opening of the mitochondrial permeability transition (PT) pore leading to the disruption of mitochondrial membrane integrity and to the dissipation of the inner transmembrane proton gradient (ΔΨ(m)). The mitochondrial PT pore is a polyprotein structure which is inhibited by the apoptosis-inhibitory oncoprotein Bcl-2 and which is closely associated with the mitochondrial benzodiazepine receptor (mBzR). Here we show that PK11195, a prototypic ligand of the 18-kDa mBzR, facilitates the induction of ΔΨ(m) disruption and subsequent apoptosis by a number of different agents, including agonists of the glucocorticoid receptor, chemotherapeutic agents (etoposide, doxorubicin), gamma irradiation, and the proapoptotic second messenger ceramide. Whereas PK11195 itself has no cytotoxic effect, it enhances apoptosis induction by these agents. This effect is not observed for benzodiazepine diazepam, whose binding site in the mBzR differs from PK11195. PK11195 partially reverses Bcl-2 mediated inhibition of apoptosis in two different cell lines. Thus, transfection-enforced Bcl-2 overexpression confers protection against glucocorticoids and chemotherapeutic agents, and this protection is largely reversed by the addition of PK11195. This effect is observed at the level of ΔΨ(m) dissipation as well as at the level of nuclear apoptosis. To gain insights into the site of action of PK11195, we performed experiments on isolated organelles. PK11195 reverses the Bcl-2- mediated mitochondrial retention of apoptogenic factors which cause isolated nuclei to undergo apoptosis in a cell-free system. Mitochondria from control cells, but not mitochondria from Bcl-2-overexpressing cells, readily release such apoptogenic factors in response to atractyloside, a ligand of the adenine nucleotide translocator. However, control and Bcl-2-overexpressing mitochondria respond equally well to a combination of atractyloside and PK11195. Altogether, these findings indicate that PK11195 abolishes apoptosis inhibition by Bcl-2 via a direct effect on mitochondria. Moreover, they suggest a novel strategy for enhancing the susceptibility of cells to apoptosis induction and, concomitantly, for reversing Bcl-2-mediated cytoprotection.
KW - Mitochondrial transmembrane potential
KW - Permeability transition
KW - Programmed cell death
UR - http://www.scopus.com/inward/record.url?scp=0032526746&partnerID=8YFLogxK
U2 - 10.1006/excr.1998.4084
DO - 10.1006/excr.1998.4084
M3 - Article
C2 - 9637784
AN - SCOPUS:0032526746
SN - 0014-4827
VL - 241
SP - 426
EP - 434
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 2
ER -