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EMBO reports 6, 9, 853–859 (2005)
doi:10.1038/sj.embor.7400488
Published online: 29 July 2005
Separate fusion of outer and inner mitochondrial membranes
Florence Malka1, Olwenn Guillery1, Carmen Cifuentes-Diaz2, Emmanuelle Guillou3, Pascale Belenguer3, Anne Lombès1 & Manuel Rojo1
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1 INSERM U582, Institut de Myologie, Université Pierre et Marie Curie, IFR14, Groupe Hospitalier Pitié-Salpêtrière, 47 blvd de l'Hôpital, 75651 Paris Cedex 13, France
2 INSERM U706/536, 17 rue de Fer à Moulin, 75005 Paris, France
3 LBCMCP, CNRS UMR 5088, Université Paul Sabatier, 118 Route de Narbonne 31062, Toulouse, France
To whom correspondence should be addressed
Manuel Rojo Tel: +33 1 42 16 57 18/17 (office/lab); Fax: +33 1 42 16 57 00; E-mail: m.rojo@myologie.chups.jussieu.fr
Received 20 December 2004; Accepted 20 June 2005; Published online 29 July 2005.
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Abstract
Mitochondria are enveloped by two closely apposed boundary membranes with different properties and functions. It is known that they undergo fusion and fission, but it has remained unclear whether outer and inner membranes fuse simultaneously, coordinately or separately. We set up assays for the study of inner and outer membrane fusion in living human cells. Inner membrane fusion was more sensitive than outer membrane fusion to inhibition of glycolysis. Fusion of the inner membrane, but not of the outer membrane, was abolished by dissipation of the inner membrane potential with K+ (valinomycin) or H+ ionophores (cccp). In addition, outer and inner membrane fusion proceeded separately in the absence of any drug. The separate fusion of outer and inner membranes and the different requirements of these fusion reactions point to the existence of fusion machineries that can function separately.
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