Hyper-O-GlcNAcylation activates nuclear factor kappa-light-chainenhancer of activated B cells (NF-kappa B) signaling through interplay with phosphorylation and acetylation

摘要

O-GlcNAcylation is the covalent addition of an O-linked beta-N-acetylglucosamine (O-GlcNAc) sugar moiety to hydroxyl groups of serine/threonine residues of cytosolic and nuclear proteins. O-GlcNAcylation, analogous to phosphorylation, plays critical roles in gene expression through direct modification of transcription factors, such as NF-kappa B. Aberrantly increased NF-kappa B O-GlcNAcylation has been linked to NF-kappa B constitutive activation and cancer development. Therefore, it is of a great biological and clinical significance to dissect the molecular mechanisms that tune NF-kappa B activity. Recently, we and others have shown that O-GlcNAcylation affects the phosphorylation and acetylation of NF-kappa B subunit p65/ RelA. However, the mechanism of how O-GlcNAcylation activates NF-kappa B signaling through phosphorylation and acetylation is not fully understood. In this study, we mappedO-GlcNAcylation sites of p65 at Thr-305, Ser319, Ser-337, Thr-352, and Ser-374. O-GlcNAcylation of p65 at Thr-305 and Ser-319 increased CREB-binding protein (CBP)/ p300-dependent activating acetylation of p65 at Lys-310, contributing to NF-kappa B transcriptional activation. Moreover, elevation of O-GlcNAcylation by overexpression of OGT increased the expression of p300, IKK alpha, and IKK beta and promoted IKKmediated activating phosphorylation of p65 at Ser-536, contributing to NF-kappa B activation. In addition, we also identified phosphorylation of p65 at Thr-308, which might impair the O-GlcNAcylation of p65 at Thr-305. These results indicate mechanisms through which both non-pathological and oncogenicO- GlcNAcylation regulate NF-kappa Bsignaling through interplay with phosphorylation and acetylation.