| 1. |
- Ho Cs, James, et al.
(författare)
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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.
- 2013
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 288:24, s. 17460-17471
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Lutay, Nataliya, et al.
(författare)
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Bacterial control of host gene expression through RNA polymerase II
- 2013
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 123:6, s. 2366-2379
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Tidskriftsartikel (refereegranskat)abstract
- The normal flora furnishes the host with ecological barriers that prevent pathogen attack while maintaining tissue homeostasis. Urinary tract infections (UTIs) constitute a highly relevant model of microbial adaptation in which some patients infected with Escherichia coil develop acute pyelonephritis, while other patients with bacteriuria exhibit an asymptomatic carrier state similar to bacterial commensalism. It remains unclear if the lack of destructive inflammation merely reflects low virulence or if carrier strains actively inhibit disease-associated responses in the host. Here, we identify a new mechanism of bacterial adaptation through broad suppression of RNA polymerase II-dependent (Pol II-dependent) host gene expression. Over 60% of all genes were suppressed 24 hours after human inoculation with the prototype asymptomatic bacteriuria (ABU) strain E. coil 83972, and inhibition was verified by infection of human cells. Specific repressors and activators of Pol II-dependent transcription were modified, Pol II phosphorylation was inhibited, and pathogen-specific signaling was suppressed in cell lines and inoculated patients. An increased frequency of strains inhibiting Pol II was epidemiologically verified in ABU and fecal strains compared with acute pyelonephritis, and a Pol II antagonist suppressed the disease-associated host response. These results suggest that by manipulating host gene expression, ABU strains promote tissue integrity while inhibiting pathology. Such bacterial modulation of host gene expression may be essential to sustain asymptomatic bacterial carriage by ensuring that potentially destructive immune activation will not occur.
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