Inhibition of A-Type K+ Channels by Urotensin-II Induces Sensory Neuronal Hyperexcitability Through the PKCα-ERK Pathway

Endocrinology. 2018 May 1;159(5):2253-2263. doi: 10.1210/en.2018-00108.

Abstract

Previous studies have implicated urotensin-II in the nociception of sensory neurons. However, to date the relevant mechanisms remain unknown. In the current study we determined the role of urotensin-II in the regulation of transient outward A-type potassium currents (IA) and neuronal excitability in trigeminal ganglion (TG) neurons. We found that application of urotensin-II to small-diameter TG neurons decreased IA in a dose-dependent manner, whereas the delayed rectifier potassium current was unaffected. The IA decrease induced by urotensin-II depended on the urotensin-II receptor (UT-R) and was associated with a hyperpolarizing shift in the steady-state inactivation curve. Exposure of TG cells to urotensin-II markedly increased protein kinase C (PKC) activity, and PKC inhibition eliminated the UT-R-mediated IA decrease. Antagonism of PKCα, either pharmacologically or genetically, but not of PKCβ prevented the decrease in IA induced by urotensin-II. Analysis of phospho-extracellular signal-regulated kinase (p-ERK) revealed that urotensin-II significantly increased the expression level of p-ERK, whereas p-p38 and p-c-Jun N-terminal kinase remained unchanged. Inhibition of mitogen-activated protein kinase/ERK signaling by the kinase antagonist U0126 and PD98059 completely abolished the UT-R-mediated IA decrease. Moreover, urotensin-II significantly increased the action potential firing rate of small TG neurons; pretreatment with 4-aminopyridine prevented this effect. In summary, our findings suggest that urotensin-II selectively attenuated IA through stimulation of the PKCα-dependent ERK1/2 signaling pathway. This UT-R-dependent mechanism might contribute to neuronal hyperexcitability in TG neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Aminopyridine / pharmacology
  • Action Potentials / drug effects*
  • Animals
  • Gene Expression / drug effects
  • MAP Kinase Signaling System / drug effects*
  • Mice
  • Patch-Clamp Techniques
  • Potassium Channel Blockers / pharmacology
  • Potassium Channels, Voltage-Gated / drug effects*
  • Potassium Channels, Voltage-Gated / metabolism
  • Protein Kinase C-alpha / drug effects*
  • Protein Kinase C-alpha / metabolism
  • Sensory Receptor Cells / drug effects*
  • Signal Transduction
  • Trigeminal Ganglion / cytology*
  • Urotensins / pharmacology*

Substances

  • Potassium Channel Blockers
  • Potassium Channels, Voltage-Gated
  • Urotensins
  • urotensin II
  • 4-Aminopyridine
  • Protein Kinase C-alpha