Mitochondrial intermembrane junctional complexes and their involvement in cell death.
Mitochondria establish contact sites between the inner and outer membranes. The contact sites are held together by junctional complexes of the adenine nucleotide translocase (ANT; inner membrane) and the voltage-dependent anion channel (VDAC; outer membrane). The junctional complexes act as multifunctional recruitment centres, binding a range of proteins according to the function to be executed. Some of these, involving kinases and enzymes of lipid transfer, are readily understood as ongoing functions in energy and lipid metabolism. But the roles of other proteins recruited to the junctional complexes are less well defined. Here, we focus on the complexes formed with Bax and with cyclophilin-D, and their possible roles in apoptotic and necrotic cell death. We have isolated both types of complexes using glutathione-S-transferase fusion proteins of Bax and of cyclophilin-D. The VDAC/ANT/cyclophilin-D complex reconstitutes Ca(2+)- and cyclosporin A-sensitive permeability transition pore activity when incorporated into proteoliposomes. The complex forms readily in the absence of factors required for pore opening in isolated mitochondria, suggesting that these factors act on the preexisting complex, rather than drive its assembly, and that the complex is a physiological entity in healthy cells.
Crompton
Martin
M
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK. m.crompton@biochemistry.ucl.ac.uk
Barksby
Emma
E
Johnson
Nicholas
N
Capano
Michela
M
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002463:Cell Membrane Permeability / Q000502:physiology; D000081406:Peptidyl-Prolyl Isomerase F; D021983:Cyclophilins / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology*; D000226:Mitochondrial ADP, ATP Translocases / Q000502:physiology*; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009336:Necrosis; D018272:Porins / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; D000081406:Peptidyl-Prolyl Isomerase F; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D018272:Porins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D021983:Cyclophilins