An Interaction between Bcl-xL and the Voltage-dependent Anion Channel (VDAC) Promotes Mitochondrial Ca2+ Uptake

• Published in: The Journal of biological chemistry Vol. 288; no. 27; pp. 19870 - 19881
• Main Authors: Huang, Huiya, Hu, Xiangxin, Eno, Colins O., Zhao, Guoping, Li, Chi, White, Carl
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05-07-2013; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Bcl-2 Proteins; bcl-X Protein - genetics; bcl-X Protein - metabolism; Calcium - metabolism; Calcium Signaling; Cells, Cultured; Embryo, Mammalian - cytology; Embryo, Mammalian - metabolism; Fibroblasts - cytology; Fibroblasts - metabolism; Imaging; Mice; Mice, Knockout; Mitochondria; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial Membranes - metabolism; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; Molecular Biophysics; Protein Binding; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein-Protein Interactions; Voltage-dependent Anion Channel; Voltage-Dependent Anion Channels - genetics; Voltage-Dependent Anion Channels - metabolism; Mitochondria; Bcl-2 Proteins; Voltage-dependent Anion Channel; Imaging; Calcium Signaling; Protein-Protein Interactions
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.448290

The role of the antiapoptotic protein Bcl-xL in regulating mitochondrial Ca2+ ([Ca2+]mito) handling was examined in wild-type (WT) and Bcl-xL knock-out (Bcl-xL-KO) mouse embryonic fibroblast cells. Inositol 1,4,5-trisphosphate-generating agonist evoked cytosolic Ca2+ transients that produced a larger [Ca2+]mito uptake in WT cells compared with Bcl-xL-KO. In permeabilized cells, stepping external [Ca2+] from 0 to 3 μm also produced a larger [Ca2+]mito uptake in WT; moreover, the [Ca2+]mito uptake capacity of Bcl-xL-KO cells was restored by re-expression of mitochondrially targeted Bcl-xL. Bcl-xL enhancement of [Ca2+]mito uptake persisted after dissipation of the mitochondrial membrane potential but was absent in mitoplasts lacking an outer mitochondrial membrane. The outer membrane-localized voltage-dependent anion channel (VDAC) is a known Ca2+ permeability pathway that directly interacts with Bcl-xL. Bcl-xL interacted with VDAC1 and -3 isoforms, and peptides based on the VDAC sequence disrupted Bcl-xL binding. Peptides reduced [Ca2+]mito uptake in WT but were without effect in Bcl-xL-KO cells. In addition, peptides reduced [Ca2+]mito uptake in VDAC1 and VDAC3 knock-out but not VDAC1 and -3 double knock-out mouse embryonic fibroblast cells, confirming that Bcl-xL interacts functionally with VDAC1 and -3 but not VDAC2. Thus, an interaction between Bcl-xL and VDAC promotes matrix Ca2+ accumulation by increasing Ca2+ transfer across the outer mitochondrial membrane.
Background: Ca2+ moves across the outer mitochondrial membrane (OMM) through the voltage-dependent anion channel (VDAC).
Results: Disrupting the interaction between VDAC and the antiapoptotic protein Bcl-xL reduces mitochondrial Ca2+ uptake.
Conclusion: Bcl-xL/VDAC interactions promote Ca2+ uptake by increasing transfer across the OMM.
Significance: Mitochondrial matrix Ca2+ is tightly regulated at the OMM by the modulation of VDAC.