Transcriptional Regulation of the Sodium-activated Potassium Channel SLICK (KCNT2) Promoter by Nuclear Factor-kappaB.

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Tomasello DL, Gancarz-Kausch AM, Dietz DM, Bhattacharjee A

Transcriptional Regulation of the Sodium-activated Potassium Channel SLICK (KCNT2) Promoter by Nuclear Factor-kappaB.

J Biol Chem. 2015 Jul 24;290(30):18575-83. doi: 10.1074/jbc.M115.643536. Epub 2015 Jun 21.

PubMed ID
26100633 [ View in PubMed
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Abstract

Although recent studies have shown the sodium-activated potassium channel SLACK (KCNT1) can contribute to neuronal excitability, there remains little information on the physiological role of the closely related SLICK (KCNT2) channel. Activation of SLICK channels may be important during pathological states such as ischemia, in which an increase in intracellular sodium and chloride can perturb membrane potential and ion homeostasis. We have identified two NFkappaB-binding sites within the promoter region of the human SLICK (KCNT2) and orthologous rat Slick (Kcnt2) genes, suggesting that conditions in which NFkappaB transcriptional activity is elevated promote expression of this channel. NFkappaB binding to the rat Slick promoter was confirmed in vivo by ChIP analyses, and NFkappaB was found differentially bound to the two sites. We verified NFkappaB transcriptional regulation of SLICK/Slick by mutational analyses and studying gene expression by luciferase assay in P19 cells, where NFkappaB is constitutively active. For the rat gene, activation of the Slick promoter was found to be additive in single NFkappaB mutations and synergistic in double mutations. Unexpectedly, for the human gene, NFkappaB exhibited cooperativity in activating the SLICK promoter. The human SLICK promoter constructs were then tested under hypoxic conditions in PC-12 cells, where NFkappaB is not active. Only under hypoxic conditions could luciferase activity be detected; the double NFkappaB mutant construct failed to exhibit activity. Transcriptional regulation of Slick by NFkappaB was verified in primary neurons. The Slick transcript decreased 24 h after NFkappaB inhibition. Our data show SLICK expression is predominantly under the control of NFkappaB. Because neuronal NFkappaB activation occurs during stressful stimuli such as hypoxia and injury, our findings suggest that SLICK is a neuroprotective gene.