title: An interaction between Bcl-xL and the voltage-dependent anion channel (VDAC) promotes mitochondrial Ca2+ uptake.
abstract: The role of the antiapoptotic protein Bcl-xL in regulating mitochondrial Ca(2+) ([Ca(2+)]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 Ca(2+) transients that produced a larger [Ca(2+)]mito uptake in WT cells compared with Bcl-xL-KO. In permeabilized cells, stepping external [Ca(2+)] from 0 to 3 μm also produced a larger [Ca(2+)]mito uptake in WT; moreover, the [Ca(2+)]mito uptake capacity of Bcl-xL-KO cells was restored by re-expression of mitochondrially targeted Bcl-xL. Bcl-xL enhancement of [Ca(2+)]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 Ca(2+) 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 [Ca(2+)]mito uptake in WT but were without effect in Bcl-xL-KO cells. In addition, peptides reduced [Ca(2+)]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 Ca(2+) accumulation by increasing Ca(2+) transfer across the outer mitochondrial membrane.
authors.affiliation: Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA.
authors.forename: Huiya
authors.initials: H
authors.lastname: Huang
authors.forename: Xiangxin
authors.initials: X
authors.lastname: Hu
authors.forename: Colins O
authors.initials: CO
authors.lastname: Eno
authors.forename: Guoping
authors.initials: G
authors.lastname: Zhao
authors.forename: Chi
authors.initials: C
authors.lastname: Li
authors.forename: Carl
authors.initials: C
authors.lastname: White
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D050994:Voltage-Dependent Anion Channels / Q000235:genetics / Q000378:metabolism*; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C494812:Bcl2l1 protein, mouse; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D050994:Voltage-Dependent Anion Channels; D051020:bcl-X Protein; D002118:Calcium
keywords: Bcl-2 Proteins; Calcium Signaling; Imaging; Mitochondria; Protein-Protein Interactions; Voltage-dependent Anion Channel