Proapoptotic N-truncated BCL-xL protein activates endogenous mitochondrial channels in living synaptic terminals.
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.
Jonas
Elizabeth A
EA
Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Hickman
John A
JA
Chachar
Mushtaque
M
Polster
Brian M
BM
Brandt
Teresa A
TA
Fannjiang
Yihru
Y
Ivanovska
Iva
I
Basañez
Gorka
G
Kinnally
Kathleen W
KW
Zimmerberg
Joshua
J
Hardwick
J Marie
JM
Kaczmarek
Leonard K
LK
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
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