Prostaglandin E2 Promotes Nav1.8 Trafficking via Its Intracellular RRR Motif Through the Protein Kinase A Pathway.

Voltage-gated sodium channels (Na_v) are essential for the initiation and propagation of action potentials in neurons. Na_v1.8 activity is regulated by prostaglandin E₂ (PGE₂). There is, however, no direct evidence showing the regulated trafficking of Na_v1.8, and the molecular and cellular mechanism of PGE₂-induced sodium channel trafficking is not clear. Here, we report that PGE₂ regulates the trafficking of Na_v1.8 through the protein kinase A (PKA) signaling pathway, and an RRR motif in the first intracellular loop of Na_v1.8 mediates this effect. In rat dorsal root ganglion (DRG) neurons, prolonged PGE₂ treatment enhanced Na_v1.8 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_v1.8. Inhibition of PKA completely blocked the PGE₂-promoted effect on Na_v1.8. Mutation of five PKA phosphorylation sites or the RRR motif in the first intracellular loop of Na_v1.8 abolished the PKA-promoted Na_v1.8 surface expression. Furthermore, a membrane-tethered peptide containing the intracellular RRR motif disrupted the PGE₂-induced promotion of the Na_v1.8 current in DRG neurons. Our data indicate that PGE₂ promotes the surface expression of Na_v1.8 via an intracellular RRR motif, and provide a novel mechanism for functional modulation of Na_v1.8 by hyperalgesic agents. [ABSTRACT FROM AUTHOR]