title: Delayed upregulation of ATP P2X3 receptors of trigeminal sensory neurons by calcitonin gene-related peptide.
abstract: Recent evidence indicates a key role for the neuropeptide calcitonin gene-related peptide (CGRP) in migraine pain, as demonstrated by the strong analgesic action of CGRP receptor antagonists, although the mechanisms of this effect remain unclear. Most trigeminal nociceptive neurons releasing CGRP also express ATP-activated purinergic P2X3 receptors to transduce pain. To understand whether the CGRP action involves P2X3 receptor modulation, the model of trigeminal nociceptive neurons in culture was used to examine the long-term action of this peptide. Although 79% of CGRP-binding neurons expressed P2X3 receptors, acute application of CGRP did not change P2X3 receptor function. Nevertheless, after 1 h of CGRP treatment, strong enhancement of the amplitude of P2X3 receptor currents was observed together with accelerated recovery from desensitization. Receptor upregulation persisted up to 10 h (despite CGRP washout), was accompanied by increased P2X3 gene transcription, and was fully prevented by the CGRP antagonist CGRP(8-37). Surface biotinylation showed CGRP augmented P2X3 receptor expression, consistent with confocal microscopy data indicating enhanced P2X3 immunoreactivity beneath the neuronal membrane. These results suggest that CGRP stimulated trafficking of P2X3 receptors to the cell-surface membrane. Using pharmacological tools, we demonstrated that this effect of CGRP was dependent on protein kinase A and PKC activation and was prevented by the trafficking inhibitor brefeldin A. Capsaicin-sensitive TRPV1 vanilloid receptors were not upregulated. The present data demonstrate a new form of selective, slow upregulation of nociceptive P2X3 receptors on trigeminal neurons by CGRP. This mechanism might contribute to pain sensitization and represents a model of neuronal plasticity in response to a migraine mediator.
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto Nazionale di Fisica della Materia Democritos National Simulation Center, International School for Advanced Studies, 34014 Trieste, Italy.
authors.forename: Elsa
authors.initials: E
authors.lastname: Fabbretti
authors.forename: Marianna
authors.initials: M
authors.lastname: D'Arco
authors.forename: Alessandra
authors.initials: A
authors.lastname: Fabbro
authors.forename: Manuela
authors.initials: M
authors.lastname: Simonetti
authors.forename: Andrea
authors.initials: A
authors.lastname: Nistri
authors.forename: Rashid
authors.initials: R
authors.lastname: Giniatullin
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004357:Drug Synergism; D004594:Electrophysiology; D051379:Mice; D008815:Mice, Inbred Strains; D009473:Neuronal Plasticity; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology; D021381:Protein Transport; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D058477:Receptors, Purinergic P2X3; D050916:TRPV Cation Channels / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014276:Trigeminal Nerve / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: C546409:P2rx3 protein, mouse; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; D000255:Adenosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D015740:Calcitonin Gene-Related Peptide