Prostaglandin E₂Promotes Na_v1.8 Trafficking via Its Intracellular RRR Motif Through the Protein Kinase A Pathway

Abstract

Voltage-gated sodium channels (Na v ) are essential for the initiation and propagation of action potentials in neurons. Na v 1.8 activity is regulated by prostaglandin E 2 (PGE 2 ). There is, however, no direct evidence showing the regulated trafficking of Na v 1.8, and the molecular and cellular mechanism of PGE 2 -induced sodium channel trafficking is not clear. Here, we report that PGE 2 regulates the trafficking of Na v 1.8 through the protein kinase A (PKA) signaling pathway, and an RRR motif in the first intracellular loop of Na v 1.8 mediates this effect. In rat dorsal root ganglion (DRG) neurons, prolonged PGE 2 treatment enhanced Na v 1.8 currents by increasing the channel density on the cell surface. Activation of PKA by forskolin had the same effect on DRG neurons and human embryonic kidney 293T cells expressing Na v 1.8. Inhibition of PKA completely blocked the PGE 2 -promoted effect on Na v 1.8. Mutation of five PKA phosphorylation sites or the RRR motif in the first intracellular loop of Na v 1.8 abolished the PKA-promoted Na v 1.8 surface expression. Furthermore, a membrane-tethered peptide containing the intracellular RRR motif disrupted the PGE 2 -induced promotion of the Na v 1.8 current in DRG neurons. Our data indicate that PGE 2 promotes the surface expression of Na v 1.8 via an intracellular RRR motif, and provide a novel mechanism for functional modulation of Na v 1.8 by hyperalgesic agents.

Exon 11 skipping ofSCN10Acoding for voltage-gated sodium channels in dorsal root ganglia

“…The putative ER retention signal (sequence RRR vs. KRR) and one of the two interaction sites (consensus SP) of p38 kinase are affected as well. Regulatory impact of such sites has been reported for rat Na V 1.8 only, [7][8][9]19 and in this study no effect of forskolin stimulation was detectable for hNa V 1.8, while currents mediated by rat Na V 1.8 was augmented. Based on a protein sequence comparison with Na V 1.8 from other species (P. troglodytes, M. mulatta, C. lupus and B. taurus) an evolutionary loss of function in exon 11 can be hypothesized.…”

PKA-Induced Internalization of Slack KNaChannels Produces Dorsal Root Ganglion Neuron Hyperexcitability

“…It is reasonable to conclude that ion channel trafficking in nociceptors is responsible for prolonged hyperalgesia. Indeed, nociceptive signals increase TRPA1 expression at the membrane through a PKA-dependent pathway (Schmidt et al, 2009), and an increased Nav1.8 surface expression after PKA activation has also been recently described (Liu et al, 2010). These studies suggest that Na ϩ entry increases in DRG neurons after PKA activation, and reducing the number of K Na channels at the plasma membrane will enhance the depolarizing effects of the increased Na ϩ currents.…”

The Chemokine CCL2 Increases Nav1.8 Sodium Channel Activity in Primary Sensory Neurons through a Gβγ-Dependent Mechanism

“…Given the fact that it is actually difficult to selectively target Na v 1.8, alternatives have been proposed like the indirect regulation of Na v 1.8 function by acting upstream via GPCR inhibition. In that respect, inflammatory mediators, such as prostaglandin, adenosine, and serotonin have been shown to influence both activity and trafficking of TTX-R sodium channels (Gold et al, 1996;Rush and Waxman, 2004;Liu et al, 2010;Ebersberger et al, 2011).…”