Release of cytochrome c and activation of pro-caspase-9 following lysosomal photodamage involves Bid cleavage.
Photodynamic therapy (PDT) protocols employing lysosomal sensitizers induce apoptosis via a mechanism that causes cytochrome c release prior to loss of mitochondrial membrane potential (DeltaPsi(m)). The current study was designed to determine how lysosomal photodamage initiates mitochondrial-mediated apoptosis in murine hepatoma 1c1c7 cells. Fluorescence microscopy demonstrated that the photosensitizer N-aspartyl chlorin e6 (NPe6) localized to the lysosomes. Irradiation of cultures preloaded with NPe6 induced the rapid destruction of lysosomes, and subsequent cleavage/activation of Bid, pro-caspases-9 and -3. Pro-caspase-8 was not activated. Release of cytochrome c occurred at about the time of Bid cleavage and preceded the loss of DeltaPsi(m). Extracts of purified lysosomes catalyzed the in vitro cleavage of cytosolic Bid, but not pro-caspase-3 activation. Pharmacological inhibition of cathepsin B, L and D activities did not suppress Bid cleavage or pro-caspases-9 and -3 activation. These studies demonstrate that photodamaged lysosomes trigger the mitochondrial apoptotic pathway by releasing proteases that activate Bid.
Reiners
J J
JJ
Institute of Environmental Health Sciences, Wayne State University, Detroit, MI 48201, USA. john.reiners.jr@wayne.edu
Caruso
J A
JA
Mathieu
P
P
Chelladurai
B
B
Yin
X-M
XM
Kessel
D
D
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000187:drug effects / Q000378:metabolism*; D002402:Cathepsin D / Q000187:drug effects / Q000378:metabolism; D002457:Cell Extracts / Q000494:pharmacology; D003574:Cytochrome c Group / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000187:drug effects / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D009369:Neoplasms / Q000201:enzymology / Q000503:physiopathology / Q000628:therapy*; D010778:Photochemotherapy; D011166:Porphyrins / Q000494:pharmacology / Q000528:radiation effects; D014407:Tumor Cells, Cultured
D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D002352:Carrier Proteins; D002457:Cell Extracts; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D011166:Porphyrins; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D002402:Cathepsin D; C053434:Talaporfin