title: Direct interaction of Bax and Bak proteins with Bcl-2 homology domain 3 (BH3)-only proteins in living cells revealed by fluorescence complementation.
abstract: The key event in the mitochondrial pathway of apoptosis is the activation of Bax and Bak by BH3-only proteins through a molecular mechanism that is still a matter of debate. Here we studied interactions among anti- and proapoptotic proteins of the Bcl-2 family in living cells by using bimolecular fluorescence complementation analysis. Our results indicate that the antiapoptotic proteins Mcl-1 and Bcl-x(L) bind preferably to the BH3-only proteins Bim, PUMA, and Noxa but can also bind to Bak and Bax. We also found a direct interaction between Bim, PUMA, or Noxa with either Bax or Bak during apoptosis induction. In HeLa cells, interaction of Bim with Bax occurs in cytosol, and then Bim-Bax complexes translocate to mitochondria. Complexes of either PUMA or Noxa with Bax or Bak were always detected at mitochondria. Overexpression of Bcl-x(L) or Mcl-1 delayed Bim/Bax translocation to mitochondria. These results reveal the ability of main BH3-only proteins to directly activate Bax and Bak in living cells and suggest that a complex network of interactions regulate the function of Bcl-2 family members during apoptosis.
authors.affiliation: Department of Biochemistry, Facultad de Ciencias, Universidad de Zaragoza, 5009 Zaragoza, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Vela
authors.forename: Oscar
authors.initials: O
authors.lastname: Gonzalo
authors.forename: Javier
authors.initials: J
authors.lastname: Naval
authors.forename: Isabel
authors.initials: I
authors.lastname: Marzo
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D016923:Cell Death; D019938:Cyclin D1 / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D015972:Gene Expression Regulation, Neoplastic; D005816:Genetic Complementation Test; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence / Q000379:methods; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D019938:Cyclin D1