Editors' ChoicePosttranslational Modifications

First Sulfhydration, Then Nitrosylation

See allHide authors and affiliations

Science Signaling  24 Jan 2012:
Vol. 5, Issue 208, pp. ec26
DOI: 10.1126/scisignal.2002879

The transcription factor nuclear factor κB (NF-κB) contributes to inflammatory signals and can exert an antiapoptotic effect by stimulating the production of genes encoding proteins that inhibit apoptosis. The p65 subunit of NF-κB is nitrosylated, which inhibits its transcriptional activity, in response to the cytokine tumor necrosis factor–α (TNF-α). Sen et al. show that the same residue that is the target for NO modification is also targeted for modification by hydrogen sulfide (H2S). TNF-α stimulated the production of H2S; increased the abundance of cystathionine-γ-lyase (CSE), the enzyme responsible for H2S synthesis; and promoted apoptosis in liver and peritoneal macrophages. All of these responses were greatly diminished or abolished in CSE-knockout mice. DNA binding of NF-κB in response to TNF-α was reduced in CSE-knockout mice, and the induction of its antiapoptotic gene targets was also reduced. Using a newly developed assay, the authors quantified relative sulfhydration and nitrosylation of p65 and found that the time course of these two modifications was inverse, with sulfhydration occurring during the early response to TNF-α and then decreasing at later times as nitrosylation increased. These time courses matched those of CSE induction (early) and induction of the NO synthesis enzyme iNOS (late) and matched the time course of enhanced interaction with the coactivator RPS3 and binding of RPS3 to the promoter of an NF-κB target gene, which occurred during the early response consistent with sulfhydration promoting NF-κB activity. Mass spectrometry and mutational analysis confirmed that sulfhydration occurred on the same residue on which nitrosylation has been shown to occur and that mutation of this residue abolished the TNF-α–induced sulfhydration of NF-κB and its interaction with RPS3 and rendered cells more sensitive to TNF-α–induced cell death. Thus, the authors propose that sequential posttranslational modification of NF-κB by sulfhydration and then nitrosylation mediates the initial activation of its transcriptional activity followed by termination of its activity.

N. Sen, B. D. Paul, M. M. Gadalla, A. K. Mustafa, T. Sen, R. Xu, S. Kim, S. H. Snyder, Hydrogen sulfide-linked sulfhydration of NF-κB mediates its antiapoptotic actions. Mol. Cell 45, 13–24 (2012). [PubMed]

Stay Connected to Science Signaling