title: Low cell cholesterol levels increase NFkappaB activity through a p38 MAPK-dependent mechanism.
abstract: Cholesterol, p38 MAPK and NFkappaB have been shown to participate in inflammation and cellular differentiation. Here, we examined the effect of cholesterol on NFkappaB-dependent transcription and the mechanisms underlying this effect in NIH3T3 cells. We show that chronic cholesterol depletion achieved with lipoprotein-deficient serum (LPDS) and 25-hydroxycholesterol (25-HC) treatment resulted in a significant increase in NFkappaB-dependent transcription, NFkappaB-DNA binding, IkappaBalpha degradation and p65/NFkappaB translocation to the nucleus, and the addition of exogenous cholesterol reversed these effects. Previously, we have shown that low cell cholesterol levels activate p38 MAPK. Here, we found that inhibition of p38 MAPK with the specific inhibitor SB203580 blocked the increase in NFkappaB activity, IkappaBalpha degradation and p65/NFkappaB translocation to the nucleus induced by cholesterol depletion. Moreover, the inhibition of the p38 MAPK downstream effector MSK1 with the specific inhibitor H89, or the overexpression of a kinase defective MSK1 abrogated the NFkappaB-dependent transcription induced by cholesterol depletion. On the other hand, the transactivation potential of p65/NFkappaB depends on phosphorylation of S276 by MSK1. We observed that cholesterol depletion increased the p65/NFkappaB transactivation capacity. This effect was reversed by cell cholesterol repletion or incubation with the SB203580 inhibitor. Moreover, the expression of a p65/NFkappaB S276A mutant was insensitive to cholesterol depletion. Together, our results demonstrate that cholesterol depletion induces NFkappaB transcriptional activity, not only by affecting the IkappaBalpha degradation and the translocation of p65/NFkappaB to the nucleus, but also regulating the p65/NFkappaB transactivating potential through a p38 MAPK/MSK1 mediated pathway.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Calleros
authors.forename: Marina
authors.initials: M
authors.lastname: Lasa
authors.forename: María J
authors.initials: MJ
authors.lastname: Toro
authors.forename: Antonio
authors.initials: A
authors.lastname: Chiloeches
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D003470:Culture Media / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D006888:Hydroxycholesterols / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D011485:Protein Binding / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000037:antagonists & inhibitors / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D003470:Culture Media; D006888:Hydroxycholesterols; D020672:I-kappa B Proteins; D007093:Imidazoles; D016328:NF-kappa B; D011725:Pyridines; D011993:Recombinant Fusion Proteins; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; C007997:25-hydroxycholesterol; D002784:Cholesterol; D008156:Luciferases; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C116919:mitogen and stress-activated protein kinase 1; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580