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HAMLET interacts with lipid membranes and perturbs their structure and integrity.

Mossberg, Anki LU ; Puchades, Maja; Halskau, Øyvind; Baumann, Anne; Lanekoff, Ingela; Chao, Yinxia; Martinez, Aurora; Svanborg, Catharina LU and Karlsson, Roger (2010) In PLoS ONE 5(2).
Abstract
BACKGROUND: Cell membrane interactions rely on lipid bilayer constituents and molecules inserted within the membrane, including specific receptors. HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded alpha-lactalbumin (HLA) and oleic acid that is internalized by tumor cells, suggesting that interactions with the phospholipid bilayer and/or specific receptors may be essential for the tumoricidal effect. This study examined whether HAMLET interacts with artificial membranes and alters membrane structure. METHODOLOGY/PRINCIPAL FINDINGS: We show by surface plasmon resonance that HAMLET binds with high affinity to surface adherent, unilamellar vesicles of lipids with varying acyl chain... (More)
BACKGROUND: Cell membrane interactions rely on lipid bilayer constituents and molecules inserted within the membrane, including specific receptors. HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded alpha-lactalbumin (HLA) and oleic acid that is internalized by tumor cells, suggesting that interactions with the phospholipid bilayer and/or specific receptors may be essential for the tumoricidal effect. This study examined whether HAMLET interacts with artificial membranes and alters membrane structure. METHODOLOGY/PRINCIPAL FINDINGS: We show by surface plasmon resonance that HAMLET binds with high affinity to surface adherent, unilamellar vesicles of lipids with varying acyl chain composition and net charge. Fluorescence imaging revealed that HAMLET accumulates in membranes of vesicles and perturbs their structure, resulting in increased membrane fluidity. Furthermore, HAMLET disrupted membrane integrity at neutral pH and physiological conditions, as shown by fluorophore leakage experiments. These effects did not occur with either native HLA or a constitutively unfolded Cys-Ala HLA mutant (rHLA(all-Ala)). HAMLET also bound to plasma membrane vesicles formed from intact tumor cells, with accumulation in certain membrane areas, but the complex was not internalized by these vesicles or by the synthetic membrane vesicles. CONCLUSIONS/SIGNIFICANCE: The results illustrate the difference in membrane affinity between the fatty acid bound and fatty acid free forms of partially unfolded HLA and suggest that HAMLET engages membranes by a mechanism requiring both the protein and the fatty acid. Furthermore, HAMLET binding alters the morphology of the membrane and compromises its integrity, suggesting that membrane perturbation could be an initial step in inducing cell death. (Less)
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author
organization
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Contribution to journal
publication status
published
subject
in
PLoS ONE
volume
5
issue
2
publisher
Public Library of Science
external identifiers
  • pmid:20186341
  • wos:000274924000023
  • scopus:77949625587
ISSN
1932-6203
DOI
10.1371/journal.pone.0009384
language
English
LU publication?
yes
id
c289b985-cfa2-410f-8eb1-304445f11785 (old id 1582843)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/20186341?dopt=Abstract
date added to LUP
2010-04-07 10:17:53
date last changed
2018-06-24 04:24:14
@article{c289b985-cfa2-410f-8eb1-304445f11785,
  abstract     = {BACKGROUND: Cell membrane interactions rely on lipid bilayer constituents and molecules inserted within the membrane, including specific receptors. HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded alpha-lactalbumin (HLA) and oleic acid that is internalized by tumor cells, suggesting that interactions with the phospholipid bilayer and/or specific receptors may be essential for the tumoricidal effect. This study examined whether HAMLET interacts with artificial membranes and alters membrane structure. METHODOLOGY/PRINCIPAL FINDINGS: We show by surface plasmon resonance that HAMLET binds with high affinity to surface adherent, unilamellar vesicles of lipids with varying acyl chain composition and net charge. Fluorescence imaging revealed that HAMLET accumulates in membranes of vesicles and perturbs their structure, resulting in increased membrane fluidity. Furthermore, HAMLET disrupted membrane integrity at neutral pH and physiological conditions, as shown by fluorophore leakage experiments. These effects did not occur with either native HLA or a constitutively unfolded Cys-Ala HLA mutant (rHLA(all-Ala)). HAMLET also bound to plasma membrane vesicles formed from intact tumor cells, with accumulation in certain membrane areas, but the complex was not internalized by these vesicles or by the synthetic membrane vesicles. CONCLUSIONS/SIGNIFICANCE: The results illustrate the difference in membrane affinity between the fatty acid bound and fatty acid free forms of partially unfolded HLA and suggest that HAMLET engages membranes by a mechanism requiring both the protein and the fatty acid. Furthermore, HAMLET binding alters the morphology of the membrane and compromises its integrity, suggesting that membrane perturbation could be an initial step in inducing cell death.},
  articleno    = {e9384},
  author       = {Mossberg, Anki and Puchades, Maja and Halskau, Øyvind and Baumann, Anne and Lanekoff, Ingela and Chao, Yinxia and Martinez, Aurora and Svanborg, Catharina and Karlsson, Roger},
  issn         = {1932-6203},
  language     = {eng},
  number       = {2},
  publisher    = {Public Library of Science},
  series       = {PLoS ONE},
  title        = {HAMLET interacts with lipid membranes and perturbs their structure and integrity.},
  url          = {http://dx.doi.org/10.1371/journal.pone.0009384},
  volume       = {5},
  year         = {2010},
}