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Changes in proteasome structure and function caused by HAMLET in tumor cells.

Gustafsson, Lotta LU ; Aits, Sonja LU ; Önnerfjord, Patrik LU ; Trulsson, Maria LU ; Storm, Petter LU and Svanborg, Catharina LU (2009) In PLoS One 4(4).
Abstract
BACKGROUND: Proteasomes control the level of endogenous unfolded proteins by degrading them in the proteolytic core. Insufficient degradation due to altered protein structure or proteasome inhibition may trigger cell death. This study examined the proteasome response to HAMLET, a partially unfolded protein-lipid complex, which is internalized by tumor cells and triggers cell death. METHODOLOGY/PRINCIPAL FINDINGS: HAMLET bound directly to isolated 20S proteasomes in vitro and in tumor cells significant co-localization of HAMLET and 20S proteasomes was detected by confocal microscopy. This interaction was confirmed by co-immunoprecipitation from extracts of HAMLET-treated tumor cells. HAMLET resisted in vitro degradation by proteasomal... (More)
BACKGROUND: Proteasomes control the level of endogenous unfolded proteins by degrading them in the proteolytic core. Insufficient degradation due to altered protein structure or proteasome inhibition may trigger cell death. This study examined the proteasome response to HAMLET, a partially unfolded protein-lipid complex, which is internalized by tumor cells and triggers cell death. METHODOLOGY/PRINCIPAL FINDINGS: HAMLET bound directly to isolated 20S proteasomes in vitro and in tumor cells significant co-localization of HAMLET and 20S proteasomes was detected by confocal microscopy. This interaction was confirmed by co-immunoprecipitation from extracts of HAMLET-treated tumor cells. HAMLET resisted in vitro degradation by proteasomal enzymes and degradation by intact 20S proteasomes was slow compared to fatty acid-free, partially unfolded alpha-lactalbumin. After a brief activation, HAMLET inhibited proteasome activity in vitro and in parallel a change in proteasome structure occurred, with modifications of catalytic (beta1 and beta5) and structural subunits (alpha2, alpha3, alpha6 and beta3). Proteasome inhibition was confirmed in extracts from HAMLET-treated cells and there were indications of proteasome fragmentation in HAMLET-treated cells. CONCLUSIONS/SIGNIFICANCE: The results suggest that internalized HAMLET is targeted to 20S proteasomes, that the complex resists degradation, inhibits proteasome activity and perturbs proteasome structure. We speculate that perturbations of proteasome structure might contribute to the cytotoxic effects of unfolded protein complexes that invade host cells. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
in
PLoS One
volume
4
issue
4
publisher
Public Library of Science
external identifiers
  • WOS:000265510000005
  • PMID:19365565
  • Scopus:65349095292
ISSN
1932-6203
DOI
10.1371/journal.pone.0005229
language
English
LU publication?
yes
id
50234907-2c4e-4149-82e7-5cac5c74cffc (old id 1392117)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/19365565?dopt=Abstract
date added to LUP
2009-05-06 13:43:36
date last changed
2016-11-27 04:27:34
@misc{50234907-2c4e-4149-82e7-5cac5c74cffc,
  abstract     = {BACKGROUND: Proteasomes control the level of endogenous unfolded proteins by degrading them in the proteolytic core. Insufficient degradation due to altered protein structure or proteasome inhibition may trigger cell death. This study examined the proteasome response to HAMLET, a partially unfolded protein-lipid complex, which is internalized by tumor cells and triggers cell death. METHODOLOGY/PRINCIPAL FINDINGS: HAMLET bound directly to isolated 20S proteasomes in vitro and in tumor cells significant co-localization of HAMLET and 20S proteasomes was detected by confocal microscopy. This interaction was confirmed by co-immunoprecipitation from extracts of HAMLET-treated tumor cells. HAMLET resisted in vitro degradation by proteasomal enzymes and degradation by intact 20S proteasomes was slow compared to fatty acid-free, partially unfolded alpha-lactalbumin. After a brief activation, HAMLET inhibited proteasome activity in vitro and in parallel a change in proteasome structure occurred, with modifications of catalytic (beta1 and beta5) and structural subunits (alpha2, alpha3, alpha6 and beta3). Proteasome inhibition was confirmed in extracts from HAMLET-treated cells and there were indications of proteasome fragmentation in HAMLET-treated cells. CONCLUSIONS/SIGNIFICANCE: The results suggest that internalized HAMLET is targeted to 20S proteasomes, that the complex resists degradation, inhibits proteasome activity and perturbs proteasome structure. We speculate that perturbations of proteasome structure might contribute to the cytotoxic effects of unfolded protein complexes that invade host cells.},
  author       = {Gustafsson, Lotta and Aits, Sonja and Önnerfjord, Patrik and Trulsson, Maria and Storm, Petter and Svanborg, Catharina},
  issn         = {1932-6203},
  language     = {eng},
  number       = {4},
  publisher    = {ARRAY(0x92c72f8)},
  series       = {PLoS One},
  title        = {Changes in proteasome structure and function caused by HAMLET in tumor cells.},
  url          = {http://dx.doi.org/10.1371/journal.pone.0005229},
  volume       = {4},
  year         = {2009},
}