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Molecular and Cellular Biology, October 2007, p. 7073-7088, Vol. 27, No. 20
0270-7306/07/$08.00+0 doi:10.1128/MCB.02116-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
,
Victor J. Yuste,1,
Gaël Roué,1,
Sandrine Barbier,1
Patricia Sancho,1
Clémence Virely,1
Manuel Rubio,2
Sylvie Baudet,3
Josep E. Esquerda,4
Hélène Merle-Béral,3
Marika Sarfati,2 and
Santos A. Susin1*
Apoptose et Système Immunitaire, CNRS-URA 1961, Institut Pasteur, 25 rue du Dr. Roux. 75015 Paris, France,1 Centre de Recherche du CHUM, Hôpital Notre-Dame, Laboratoire d'Immunorégulation, 1560 Sherbrooke St. East, Montréal, QC H2L 4M1, Canada,2 Service d'Hématologie Biologique, Groupe Hospitalier Pitie-Salpêtrière, Paris, France,3 Unitat de Neurobiologia Cellular, Departament de Ciencies Mediques Basiques, Facultat de Medicina, Lleida, Spain4
Received 13 November 2006/ Returned for modification 14 February 2007/ Accepted 24 July 2007
Ligation of CD47 triggers caspase-independent programmed cell death (PCD) in normal and leukemic cells. Here, we characterize the morphological and biochemical features of this type of death and show that it displays the hallmarks of type III PCD. A molecular and biochemical approach has led us to identify a key mediator of this type of death, dynamin-related protein 1 (Drp1). CD47 ligation induces Drp1 translocation from cytosol to mitochondria, a process controlled by chymotrypsin-like serine proteases. Once in mitochondria, Drp1 provokes an impairment of the mitochondrial electron transport chain, which results in dissipation of mitochondrial transmembrane potential, reactive oxygen species generation, and a drop in ATP levels. Surprisingly, neither the activation of the most representative proapoptotic members of the Bcl-2 family, such as Bax or Bak, nor the release of apoptogenic proteins AIF (apoptosis-inducing factor), cytochrome c, endonuclease G (EndoG), Omi/HtrA2, or Smac/DIABLO from mitochondria to cytosol is observed. Responsiveness of cells to CD47 ligation increases following Drp1 overexpression, while Drp1 downregulation confers resistance to CD47-mediated death. Importantly, in B-cell chronic lymphocytic leukemia cells, mRNA levels of Drp1 strongly correlate with death sensitivity. Thus, this previously unknown mechanism controlling caspase-independent type III PCD may provide the basis for novel therapeutic approaches to overcome apoptotic avoidance in malignant cells.
Published ahead of print on 6 August 2007.
Supplemental material for this article may be found at http://mcb.asm.org/.
M.B., V.J.Y., and G.R. should be considered first authors.
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