Granzyme B enters the mitochondria in a Sam50-, Tim22- and mtHsp70-dependent manner to induce apoptosis.
We have found that granzyme B (GB)-induced apoptosis also requires reactive oxygen species resulting from the alteration of mitochondrial complex I. How GB, which does not possess a mitochondrial targeting sequence, enter this organelle is unknown. We show that GB enters the mitochondria independently of the translocase of the outer mitochondrial membrane complex, but requires instead Sam50, the central subunit of the sorting and assembly machinery that integrates outer membrane β-barrel proteins. Moreover, GB breaches the inner membrane through Tim22, the metabolite carrier translocase pore, in a mitochondrial heat-shock protein 70 (mtHsp70)-dependent manner. Granzyme A (GA) and caspase-3 use a similar route to the mitochondria. Finally, preventing GB from entering the mitochondria either by mutating lysine 243 and arginine 244 or depleting Sam50 renders cells more resistant to GB-mediated reactive oxygen species and cell death. Similarly, Sam50 depletion protects cells from GA-, GM- and caspase-3-mediated cell death. Therefore, cytotoxic molecules enter the mitochondria to induce efficiently cell death through a noncanonical Sam50-, Tim22- and mtHsp70-dependent import pathway.
Department of Cell Physiology and Metabolism, University of Geneva, Rue Michel-Servet-1, Geneva, Switzerland.
Valentina
V
Chiusolo
Department of Cell Physiology and Metabolism, University of Geneva, Rue Michel-Servet-1, Geneva, Switzerland.
Guillaume
G
Jacquemin
Department of Cell Physiology and Metabolism, University of Geneva, Rue Michel-Servet-1, Geneva, Switzerland.
Esen
E
Yonca Bassoy
Department of Radiology and Medical Informatics, Geneva University Hospital, Geneva, Switzerland.|Institute of Translational Molecular Imaging, University of Geneva, Geneva, Switzerland.
Laurent
L
Vinet
IBS/Groupe Channels, 71 avenue des Martyrs CS 10090, Grenoble 38044, France.
Lavinia
L
Liguori
Anatomy Unit, Department of Medicine, University of Fribourg, Fribourg, Switzerland.
Michael
M
Walch
Biozentrum Department of Microbiology, Am Hubland, Würzburg 97074, Germany.
Vera
V
Kozjak-Pavlovic
Department of Cell Physiology and Metabolism, University of Geneva, Rue Michel-Servet-1, Geneva, Switzerland.
Denis
D
Martinvalet
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000633:toxicity; D042967:Electron Transport Complex I / Q000378:metabolism; D053804:Granzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014634:Valinomycin / Q000633:toxicity
D018840:HSP70 Heat-Shock Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D000090622:Mitochondrial Precursor Protein Import Complex Proteins; D024101:Mitochondrial Proteins; D011993:Recombinant Fusion Proteins; C522815:SAMM50 protein, human; C455940:mitochondrial outer membrane protein 35-kDa, mouse; D014634:Valinomycin; D004317:Doxorubicin; C509213:GZMB protein, human; C509218:GZMM protein, human; D053804:Granzymes; C509212:GZMA protein, human; D053148:Caspase 3; D042967:Electron Transport Complex I