Regulation of the Kv7.2/3 Channels by the Neuronal Serum-and Gluococorticoids-Regulated Kinase 1.1

Abstract

Voltage gated K+ channels are key regulators of neuronal excitability. The M-Current, formed by tetramerization of Kv7.2 and Kv7.3 subunits, is a voltage gated K+ current present in neurons. The inhibition of this current leads to depolarization of the membrane potential. It has been described previously that the serum-and glucocorticoid regulated kinase 1 (SGK1) induces an increase in the amount of Kv7.2/3 channels in the membrane (Schuetz et al. 2008). We now show that the neuronal isoform of this kinase (SGK1.1) induces an up-regulation of the Kv7.2/3 current in Xenopus laevis oocytes, while the kinase-inactive mutant K220A does not produce an effect. SGK1.1 interacts with PIP2 and is normally localized to the plasma membrane (Arteaga et al. 2008). An SGK1.1 mutant disrupting PIP2 binding (K21N/K22N/R23G; Wesch et al. 2010) had no effect in the amplitude of the Kv7.2/3 current. SGK1.1 did not modify the voltage dependence and open or close kinetics of the Kv7.2/3 channels, suggesting that the kinase alters channel abundance in the membrane. We also tested M-current amplitude in neurons of the superior cervical ganglion (SCG) isolated from transgenic mice expressing a constitutively active form of SGK1.1 (S515D). Transgenic SCG neurons showed an increase in M-current amplitude, consistent with a trend towards a more negative resting potential and less excitability when compared with wild-type SCG neurons. Our conclusions are:• SGK1.1 is a novel regulator of M-channels.• SGK1.1 could be an integrator of different signal transduction pathways controlling M-channels and therefore neuronal excitability.