title: Proapoptotic N-truncated BCL-xL protein activates endogenous mitochondrial channels in living synaptic terminals.
abstract: Neuronal death is often preceded by functional alterations at nerve terminals. Anti- and proapoptotic BCL-2 family proteins not only regulate the neuronal death pathway but also affect excitability of healthy neurons. We found that exposure of squid stellate ganglia to hypoxia, a death stimulus for neurons, causes a cysteine protease-dependent loss of full-length antiapoptotic BCL-xL, similar to previous findings in mammalian cells. Therefore, to determine the direct effect of the naturally occurring proapoptotic cleavage product of BCL-xL on mitochondria, recombinant N-truncated BCL-xL was applied to mitochondria inside the squid presynaptic terminal and to purified mitochondria isolated from yeast. N-truncated BCL-xL rapidly induced large multi-conductance channels with a maximal conductance significantly larger than those produced by full-length BCL-xL. This activity required the hydrophobic C terminus and the BH3 domain of BCL-xL. Moreover, N-truncated BCL-xL failed to produce any channel activity when applied to plasma membranes, suggesting that a component of the mitochondrial membrane is necessary for its actions. Consistent with this idea, the large channels induced by N-truncated BCL-xL are inhibited by NADH and require the presence of VDAC, a voltage-dependent anion channel present in the outer mitochondrial membrane. These observations suggest that the mitochondrial channels specific to full-length and N-truncated BCL-xL contribute to their opposite effects on synaptic transmission, and are consistent with their opposite effects on the cell death pathway.
authors.affiliation: Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Jonas
authors.forename: John A
authors.initials: JA
authors.lastname: Hickman
authors.forename: Mushtaque
authors.initials: M
authors.lastname: Chachar
authors.forename: Brian M
authors.initials: BM
authors.lastname: Polster
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Brandt
authors.forename: Yihru
authors.initials: Y
authors.lastname: Fannjiang
authors.forename: Iva
authors.initials: I
authors.lastname: Ivanovska
authors.forename: Gorka
authors.initials: G
authors.lastname: Basañez
authors.forename: Kathleen W
authors.initials: KW
authors.lastname: Kinnally
authors.forename: Joshua
authors.initials: J
authors.lastname: Zimmerberg
authors.forename: J Marie
authors.initials: JM
authors.lastname: Hardwick
authors.forename: Leonard K
authors.initials: LK
authors.lastname: Kaczmarek
mesh_terms: D000818:Animals; D017209:Apoptosis; D049832:Decapodiformes; D004553:Electric Conductivity; D010450:Endopeptidases / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D007473:Ion Channels / Q000819:agonists* / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D018272:Porins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion / Q000235:genetics*; D050994:Voltage-Dependent Anion Channels; D051020:bcl-X Protein
chemical_list: D007473:Ion Channels; D008081:Liposomes; D018272:Porins; D019253:Proto-Oncogene Proteins c-bcl-2; D050994:Voltage-Dependent Anion Channels; D051020:bcl-X Protein; D009243:NAD; D010450:Endopeptidases