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A folding variant of human alpha-lactalbumin induces mitochondrial permeability transition in isolated mitochondria

Köhler, Camilla; Gogvadze, Vladimir; Håkansson, Anders P LU ; Svanborg, Catharina LU ; Orrenius, Sten and Zhivotovsky, Boris (2001) In European Journal of Biochemistry 268(1). p.186-191
Abstract
A human milk fraction containing multimeric alpha-lactalbumin (MAL) is able to kill cells via apoptosis. MAL is a protein complex of a folding variant of alpha-lactalbumin and lipids. Previous results have shown that upon treatment of transformed cells, MAL localizes to the mitochondria and cytochrome c is released into the cytosol. This is followed by activation of the caspase cascade. In this study, we further investigated the involvement of mitochondria in apoptosis induced by the folding variant of alpha-lactalbumin. Addition of MAL to isolated rat liver mitochondria induced a loss of the mitochondrial membrane potential (Delta Psi(m)), mitochondrial swelling and the release of cytochrome c. These changes were Ca(2+)-dependent and were... (More)
A human milk fraction containing multimeric alpha-lactalbumin (MAL) is able to kill cells via apoptosis. MAL is a protein complex of a folding variant of alpha-lactalbumin and lipids. Previous results have shown that upon treatment of transformed cells, MAL localizes to the mitochondria and cytochrome c is released into the cytosol. This is followed by activation of the caspase cascade. In this study, we further investigated the involvement of mitochondria in apoptosis induced by the folding variant of alpha-lactalbumin. Addition of MAL to isolated rat liver mitochondria induced a loss of the mitochondrial membrane potential (Delta Psi(m)), mitochondrial swelling and the release of cytochrome c. These changes were Ca(2+)-dependent and were prevented by cyclosporin A, an inhibitor of mitochondrial permeability transition. MAL also increased the rate of state 4 respiration in isolated mitochondria by exerting an uncoupling effect. This effect was due to the presence of fatty acids in the MAL complex because it was abolished completely by BSA. BSA delayed, but failed to prevent, mitochondrial swelling as well as dissipation of Delta Psi(m), indicating that the fatty acid content of MAL facilitated, rather than caused, these effects. Similar results were obtained with HAMLET (human alpha-lactalbumin made lethal to tumour cells), which is native alpha-lactalbumin converted in vitro to the apoptosis-inducing folding variant of the protein in complex with oleic acid. Our findings demonstrate that a folding variant of alpha-lactalbumin induces mitochondrial permeability transition with subsequent cytochrome c release, which in transformed cells may lead to activation of the caspase cascade and apoptotic death. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
α-lactalbumin • cytochrome c • mitochondria • mitochondrial permeability transition • tumour cells
in
European Journal of Biochemistry
volume
268
issue
1
pages
186 - 191
publisher
Wiley-Blackwell
external identifiers
  • pmid:11121120
  • scopus:0035160316
ISSN
0014-2956
DOI
language
English
LU publication?
yes
id
e525e421-e360-43cf-9c19-ef304618663b (old id 1121128)
date added to LUP
2008-07-01 14:34:30
date last changed
2018-06-03 04:27:49
@article{e525e421-e360-43cf-9c19-ef304618663b,
  abstract     = {A human milk fraction containing multimeric alpha-lactalbumin (MAL) is able to kill cells via apoptosis. MAL is a protein complex of a folding variant of alpha-lactalbumin and lipids. Previous results have shown that upon treatment of transformed cells, MAL localizes to the mitochondria and cytochrome c is released into the cytosol. This is followed by activation of the caspase cascade. In this study, we further investigated the involvement of mitochondria in apoptosis induced by the folding variant of alpha-lactalbumin. Addition of MAL to isolated rat liver mitochondria induced a loss of the mitochondrial membrane potential (Delta Psi(m)), mitochondrial swelling and the release of cytochrome c. These changes were Ca(2+)-dependent and were prevented by cyclosporin A, an inhibitor of mitochondrial permeability transition. MAL also increased the rate of state 4 respiration in isolated mitochondria by exerting an uncoupling effect. This effect was due to the presence of fatty acids in the MAL complex because it was abolished completely by BSA. BSA delayed, but failed to prevent, mitochondrial swelling as well as dissipation of Delta Psi(m), indicating that the fatty acid content of MAL facilitated, rather than caused, these effects. Similar results were obtained with HAMLET (human alpha-lactalbumin made lethal to tumour cells), which is native alpha-lactalbumin converted in vitro to the apoptosis-inducing folding variant of the protein in complex with oleic acid. Our findings demonstrate that a folding variant of alpha-lactalbumin induces mitochondrial permeability transition with subsequent cytochrome c release, which in transformed cells may lead to activation of the caspase cascade and apoptotic death.},
  author       = {Köhler, Camilla and Gogvadze, Vladimir and Håkansson, Anders P and Svanborg, Catharina and Orrenius, Sten and Zhivotovsky, Boris},
  issn         = {0014-2956},
  keyword      = {α-lactalbumin • cytochrome c • mitochondria • mitochondrial permeability transition • tumour cells},
  language     = {eng},
  number       = {1},
  pages        = {186--191},
  publisher    = {Wiley-Blackwell},
  series       = {European Journal of Biochemistry},
  title        = {A folding variant of human alpha-lactalbumin induces mitochondrial permeability transition in isolated mitochondria},
  url          = {http://dx.doi.org/},
  volume       = {268},
  year         = {2001},
}