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Lipids as Tumoricidal Components of Human Alpha-lactalbumin Made Lethal to Tumor Cells (HAMLET); Unique and Shared Effects on Signaling and Death.

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Author

Summary, in English

Long-chain fatty acids (LCFAs) are internalized by receptor-mediated mechanisms or receptor-independent diffusion across cytoplasmic membranes and are utilized as nutrients, building blocks and signaling intermediates. Here we describe how the association of LCFAs to a partially unfolded, extracellular protein can alter the presentation to target cells and cellular effects. HAMLET (Human α-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded α-lactalbumin and oleic acid (OA). As OA lacks independent tumoridical activity at concentrations equimolar to HAMLET, the contribution of the lipid has been debated. We show by natural abundance 13C NMR that the lipid in HAMLET is deprotonated and by chromatography that oleate rather than oleic acid is the relevant HAMLET constituent. Compared to HAMLET, oleate (175 μM) showed weak effects on ion fluxes and gene expression. Unlike HAMLET, which causes metabolic paralysis, fatty acid metabolites were less strongly altered. The functional overlap increased with higher oleate concentrations (500 uM). Cellular responses to OA were weak or absent, suggesting that deprotonation favors cellular interactions of fatty acids. Fatty acids may thus exert some of their essential effects on host cells when in the deprotonated state and when presented in the context of a partially unfolded protein.

Publishing year

2013

Language

English

Pages

17460-17471

Publication/Series

Journal of Biological Chemistry

Volume

288

Issue

24

Document type

Journal article

Publisher

American Society for Biochemistry and Molecular Biology

Topic

  • Endocrinology and Diabetes
  • Microbiology in the medical area
  • Immunology in the medical area

Status

Published

Research group

  • Genomics, Diabetes and Endocrinology

ISBN/ISSN/Other

  • ISSN: 1083-351X