title: Lipids as tumoricidal components of human α-lactalbumin made lethal to tumor cells (HAMLET): unique and shared effects on signaling and death.
abstract: Long-chain fatty acids 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 long-chain fatty acids 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 tumoricidal activity at concentrations equimolar to HAMLET, the contribution of the lipid has been debated. We show by natural abundance (13)C NMR that the lipid in HAMLET is deprotonated and by chromatography that oleate rather than oleic acid is the relevant HAMLET constituent. Compared with 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 μm). 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.
authors: Department of Microbiology, Immunology, and Glycobiology (MIG), Institute of Laboratory Medicine, Lund University, Sölvegatan 23, S-223 62 Lund, Sweden.
authors: James C S
authors: JC
authors: Ho
authors: Petter
authors: P
authors: Storm
authors: Anna
authors: A
authors: Rydström
authors: Ben
authors: B
authors: Bowen
authors: Fredrik
authors: F
authors: Alsin
authors: Louise
authors: L
authors: Sullivan
authors: Inès
authors: I
authors: Ambite
authors: K H
authors: KH
authors: Mok
authors: Trent
authors: T
authors: Northen
authors: Catharina
authors: C
authors: Svanborg
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002952:Citric Acid Cycle / Q000187:drug effects; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks; D006801:Humans; D019169:Jurkat Cells; D007768:Lactalbumin / Q000737:chemistry / Q000494:pharmacology*; D055442:Metabolome / Q000187:drug effects; D019301:Oleic Acid / Q000737:chemistry / Q000494:pharmacology*; D009829:Oleic Acids / Q000737:chemistry / Q000494:pharmacology*; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction / Q000187:drug effects*; D059467:Transcriptome / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; C506422:HAMLET complex, human; D009829:Oleic Acids; D019301:Oleic Acid; C013173:osteum; D007768:Lactalbumin
keywords: Cancer Biology; Cell Death; HAMLET; Lipid Metabolism; Lipids; Oleate; Oleic Acid; Protein Complexes; Protein Folding
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