title: Mitochondrial proteomic approach reveals galectin-7 as a novel BCL-2 binding protein in human cells.
abstract: Although the anti-apoptotic activity of Bcl-2 has been extensively studied, its mode of action remains incompletely understood. Deciphering the network of Bcl-2 interacting factors is necessary to better understand the key function of Bcl-2 in apoptosis initiation. To identify novel Bcl-2 mitochondrial partners, we have combined a Bcl-2 immunocapture with a mass spectrometry analysis using highly pure mitochondrial fractions isolated from human cancer cells. We identified at high confidence 127 potential Bcl-2-interacting proteins. Gene ontology mining reveals enrichment for mitochondrial proteins, endoplasmic reticulum-associated proteins, and cytoskeleton-associated proteins. Importantly, we report the identification of galectin-7 (Gal7), a member of a family of β-galactoside-binding lectins that was already known to exhibit a pro-apoptotic function, as a new mitochondrial Bcl-2 interacting partner. Our data further show that endogenous Bcl-2 coimmunoprecipitates with Gal7 and that recombinant Gal7 directly interacts with recombinant Bcl-2. A fraction of Gal7 is constitutively localized at mitochondria in a Bcl-2-dependent manner and sensitizes the mitochondria to the apoptotic signal. In addition, we show that the Bcl-2/Gal7 interaction is abolished following genotoxic stress. Taken together, our findings suggest that the binding of Gal7 to Bcl-2 may constitute a new target for enhancing the intrinsic apoptosis pathway.
authors.affiliation: LBCMCP, CNRS-UMR5088 IPBS, CNRS-UMR5089, Université de Toulouse, 31077 Toulouse, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Villeneuve
authors.forename: Laurent
authors.initials: L
authors.lastname: Baricault
authors.forename: Ludovic
authors.initials: L
authors.lastname: Canelle
authors.forename: Nadia
authors.initials: N
authors.lastname: Barboule
authors.forename: Carine
authors.initials: C
authors.lastname: Racca
authors.forename: Bernard
authors.initials: B
authors.lastname: Monsarrat
authors.forename: Thierry
authors.initials: T
authors.lastname: Magnaldo
authors.forename: Florence
authors.initials: F
authors.lastname: Larminat
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D037161:Galectins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D060066:Protein Interaction Maps; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D037161:Galectins; C092525:LGALS7 protein, human; D024101:Mitochondrial Proteins; D019253:Proto-Oncogene Proteins c-bcl-2