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XB-ART-46668
J Neurosci 2013 Feb 06;336:2684-96. doi: 10.1523/JNEUROSCI.3442-12.2013.
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The neuronal serum- and glucocorticoid-regulated kinase 1.1 reduces neuronal excitability and protects against seizures through upregulation of the M-current.

Miranda P , Cadaveira-Mosquera A , González-Montelongo R , Villarroel A , González-Hernández T , Lamas JA , Alvarez de la Rosa D , Giraldez T .


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The M-current formed by tetramerization of Kv7.2 and Kv7.3 subunits is a neuronal voltage-gated K(+) conductance that controls resting membrane potential and cell excitability. In Xenopus laevis oocytes, an increase in Kv7.2/3 function by the serum- and glucocorticoid-regulated kinase 1 (SGK1) has been reported previously (Schuetz et al., 2008). We now show that the neuronal isoform of this kinase (SGK1.1), with distinct subcellular localization and modulation, upregulates the Kv7.2/3 current in Xenopus oocytes and mammalian human embryonic kidney HEK293 cells. In contrast to the ubiquitously expressed SGK1, the neuronal isoform SGK1.1 interacts with phosphoinositide-phosphatidylinositol 4,5-bisphosphate (PIP(2)) and is distinctly localized to the plasma membrane (Arteaga et al., 2008). An SGK1.1 mutant with disrupted PIP(2) binding sites produced no effect on Kv7.2/3 current amplitude. SGK1.1 failed to modify the voltage dependence of activation and did not change activation or deactivation kinetics of Kv7.2/3 channels. These results suggest that the kinase increases channel membrane abundance, which was confirmed with flow cytometry assays. To evaluate the effect of the kinase in neuronal excitability, we generated a transgenic mouse (Tg.sgk) expressing a constitutively active form of SGK1.1 (S515D). Superior cervical ganglion (SCG) neurons isolated from Tg.sgk mice showed a significant increase in M-current levels, paralleled by reduced excitability and more negative resting potentials. SGK1.1 effect on M-current in Tg.sgk-SCG neurons was counteracted by muscarinic receptor activation. Transgenic mice with increased SGK1.1 activity also showed diminished sensitivity to kainic acid-induced seizures. Altogether, our results unveil a novel role of SGK1.1 as a physiological regulator of the M-current and neuronal excitability.

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Species referenced: Xenopus laevis
Genes referenced: sgk1 tbx2

References [+] :
Alvarez de la Rosa, The serum and glucocorticoid kinase sgk increases the abundance of epithelial sodium channels in the plasma membrane of Xenopus oocytes. 1999, Pubmed, Xenbase