title: Zn2+-induced NF-kappaB-dependent transcriptional activity involves site-specific p65/RelA phosphorylation.
abstract: Zinc is an essential micronutrient, but is proinflammatory when inhaled into the lung. While it is recognized that zinc exposure of airway epithelial cells activates the transcription factor NF-kappaB and increases the expression of inflammatory cytokines to mediate this response, the underlying mechanism of NF-kappaB activation remains to be characterized. In this study, we investigated these Zn2+-induced signaling mechanisms in the BEAS-2B human airway epithelial cell line. Fifty micromolars Zn2+ induced NF-kappaB-dependent transcriptional activity. However, this occurred independently of IkappaBalpha degradation, an essential event in activation of the canonical NF-kappaB pathway, which is induced by physiological stimuli such as TNFalpha and IL-1beta. We also observed that 50 microM Zn2+ exposure caused p65/RelA phosphorylation on Ser 276, Ser 529, and Ser 536 in both cytoplasmic and nuclear cell fractions. Mutational analysis pointed to Ser 536 of p65/RelA as the determinant of Zn2+-induced NF-kappaB transactivation in BEAS-2B cells. Pharmacological inhibition of IKKalpha/beta activity reduced both Zn2+-induced p65/RelA phosphorylation at Ser 536 and NF-kappaB-dependent transcriptional activity, suggesting that IKKalpha/beta is necessary for these Zn2+-induced effects. Taken together, these data show that exposure to supraphysiological concentrations of Zn2+ induces NF-kappaB-dependent transcription through an alternate mechanism, suggesting a novel pathway for cellular responses to environmental stress.
authors.affiliation: Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, NC, USA.
authors.forename: Yu-Mee
authors.initials: YM
authors.lastname: Kim
authors.forename: Dongsun
authors.initials: D
authors.lastname: Cao
authors.forename: William
authors.initials: W
authors.lastname: Reed
authors.forename: Weidong
authors.initials: W
authors.lastname: Wu
authors.forename: Ilona
authors.initials: I
authors.lastname: Jaspers
authors.forename: Tamara
authors.initials: T
authors.lastname: Tal
authors.forename: Philip A
authors.initials: PA
authors.lastname: Bromberg
authors.forename: James M
authors.initials: JM
authors.lastname: Samet
mesh_terms: D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D002999:Clone Cells; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism; D051996:Transcription Factor RelA / Q000737:chemistry* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D016328:NF-kappa B; D051996:Transcription Factor RelA; D012694:Serine; D015032:Zinc