Protein kinase A anchoring via AKAP150 is essential for TRPV1 modulation by forskolin and prostaglandin E₂ in mouse sensory neurons

Phosphorylation-dependent modulation of the vanilloid receptor TRPV1 is one of the key mechanisms mediating the hyperalgesic effects of inflammatory mediators, such as prostaglandin E₂ (PGE₂). However, little is known about the molecular organization of the TRPV1 phosphorylation complex and specifically about scaffolding proteins that position the protein kinase A (PKA) holoenzyme proximal to TRPV1 for effective and selective regulation of the receptor. Here, we demonstrate the critical role of the A-kinase anchoring protein AKAP150 in PKA-dependent modulation of TRPV1 function in adult mouse dorsal root ganglion (DRG) neurons. We found that AKAP150 is expressed in ∼80% of TRPV1-positive DRG neurons and is coimmunoprecipitated with the capsaicin receptor. In functional studies, PKA stimulation with forskolin markedly reduced desensitization of TRPV1. This effect was blocked by the PKA selective inhibitors KT5720 [(9S,10R,12R)-2,3,9,10,11,12-hexahydro-10- hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′, 1′-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylicacid hexyl ester] and H89 (N-[2-( p-bromo-cinnamylamino)-ethyl]-5-isoquinoline-sulfon-amide 2HCl), as well as by the AKAP inhibitory peptide Ht31. Similarly, PGE₂ decreased TRPV1 desensitization in a manner sensitive to the PKA inhibitor KT5720. Both the forskolin and PGE₂ effects were strongly impaired in DRG neurons from knock-in mice that express a mutant AKAP150 lacking the PKA-binding domain (Δ36 mice). Protein kinase C-dependent sensitization of TRPV1 remained intact in Δ36 mice. The PGE₂/PKA signaling defect in DRG neurons from Δ36 mice was rescued by overexpressing the full-length human ortholog of AKAP150 in these cells. In behavioral testing, PGE₂-induced thermal hyperalgesia was significantly diminished in Δ36 mice. Together, these data suggest that PKA anchoring by AKAP150 is essential for the enhancement of TRPV1 function by activation of the PGE ₂/PKA signaling pathway.