AKAP‐dependent sensitization ofCav3.2 channels via theEP4receptor/cAMPpathway mediatesPGE2‐induced mechanical hyperalgesia

Abstract

Background and PurposeTheCav3.2 isoform ofT‐typeCa2+channels (Tchannels) is sensitized by hydrogen sulfide, a pro‐nociceptive gasotransmitter, and also byPKAthat mediatesPGE2‐induced hyperalgesia. Here we examined and analysedCav3.2 sensitization via thePGE2/cAMPpathway inNG108‐15 cells that expressCav3.2 and produce cAMPin response toPGE2, and its impact on mechanical nociceptive processing in rats.Experimental ApproachInNG108‐15 cells and rat dorsal root ganglion (DRG) neurons,T‐channel‐dependent currents (Tcurrents) were measured with the whole‐cell patch‐clamp technique. The molecular interaction ofCav3.2 with A‐kinase anchoring protein 150 (AKAP150) and its phosphorylation were analysed by immunoprecipitation/immunoblotting inNG108‐15 cells. Mechanical nociceptive threshold was determined by the paw pressure test in rats.Key ResultsInNG108‐15 cells and/or ratDRGneurons, dibutyryl cAMP(db‐cAMP) orPGE2increasedTcurrents, an effect blocked byAKAPSt‐Ht31 inhibitor peptide (AKAPI) orKT5720, aPKAinhibitor. The effect ofPGE2was abolished byRQ‐00015986‐00, anEP4receptor antagonist.AKAP150 was co‐immunoprecipitated withCav3.2, regardless of stimulation with db‐cAMP, andCav3.2 was phosphorylated by db‐cAMPorPGE2. In rats, intraplantar (i.pl.) administration of db‐cAMPorPGE2caused mechanical hyperalgesia, an effect suppressed byAKAPI, two distinctT‐channel blockers,NNC55‐0396 and ethosuximide, or ZnCl2, known to inhibitCav3.2 amongTchannels. Oral administration ofRQ‐00015986‐00 suppressed thePGE2‐induced mechanical hyperalgesia.Conclusion and ImplicationsOur findings suggest thatPGE2causesAKAP‐dependent phosphorylation and sensitization ofCav3.2 through theEP4receptor/cAMP/PKApathway, leading to mechanical hyperalgesia in rats.