Electrophysiological study of a novel large pore formed by Bax and the voltage-dependent anion channel that is permeable to cytochrome c.
The Bcl-2 family of proteins, consisting of anti-apoptotic and pro-apoptotic members, regulates cell death by controlling mitochondrial membrane permeability that is crucial for apoptotic signal transduction. We have recently shown that some of these proteins, such as Bcl-x(L), Bax, and Bak, directly modulate the mitochondrial voltage-dependent anion channel (VDAC) and thus regulate apoptogenic cytochrome c release and potential loss. To elucidate the molecular mechanisms of VDAC regulation by Bcl-2 family proteins, an electrophysiological study was carried out. It was found that VDAC and pro-apoptotic Bax created a large pore, with conductance levels 4- and 10-fold greater than those of the VDAC and Bax channels, respectively. Although the VDAC and Bax channels both show ion selectivity and voltage-dependent modulation of their activity, the VDAC-Bax channel had neither of their properties. Anti-apoptotic Bcl-x(L) and its BH4 oligopeptide completely closed the VDAC, in contrast to the Bax. Cytochrome c passed through a single VDAC-Bax channel but not through the VDAC or Bax channel in a planar lipid bilayer. These data provide direct evidence that VDAC forms a novel large pore together with Bax.
Shimizu
S
S
Department of Medical Genetics, Biomedical Research Center, CREST of Japan Science and Technology Corp., 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Ide
T
T
Yanagida
T
T
Tsujimoto
Y
Y
D000818:Animals; D002460:Cell Line; D010856:Columbidae; D003574:Cytochrome c Group / Q000378:metabolism*; D004594:Electrophysiology; D006736:Horses; D006801:Humans; D008928:Mitochondria / Q000502:physiology*; D010539:Permeability; D018272:Porins / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013329:Structure-Activity Relationship; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494826:BAX protein, human; C494811:BCL2L1 protein, human; D003574:Cytochrome c Group; D018272:Porins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein