title: Critical role for Epac1 in inflammatory pain controlled by GRK2-mediated phosphorylation of Epac1.
abstract: cAMP signaling plays a key role in regulating pain sensitivity. Here, we uncover a previously unidentified molecular mechanism in which direct phosphorylation of the exchange protein directly activated by cAMP 1 (EPAC1) by G protein kinase 2 (GRK2) suppresses Epac1-to-Rap1 signaling, thereby inhibiting persistent inflammatory pain. Epac1(-/-) mice are protected against inflammatory hyperalgesia in the complete Freund's adjuvant (CFA) model. Moreover, the Epac-specific inhibitor ESI-09 inhibits established CFA-induced mechanical hyperalgesia without affecting normal mechanical sensitivity. At the mechanistic level, CFA increased activity of the Epac target Rap1 in dorsal root ganglia of WT, but not of Epac1(-/-), mice. Using sensory neuron-specific overexpression of GRK2 or its kinase-dead mutant in vivo, we demonstrate that GRK2 inhibits CFA-induced hyperalgesia in a kinase activity-dependent manner. In vitro, GRK2 inhibits Epac1-to-Rap1 signaling by phosphorylation of Epac1 at Ser-108 in the Disheveled/Egl-10/pleckstrin domain. This phosphorylation event inhibits agonist-induced translocation of Epac1 to the plasma membrane, thereby reducing Rap1 activation. Finally, we show that GRK2 inhibits Epac1-mediated sensitization of the mechanosensor Piezo2 and that Piezo2 contributes to inflammatory mechanical hyperalgesia. Collectively, these findings identify a key role of Epac1 in chronic inflammatory pain and a molecular mechanism for controlling Epac1 activity and chronic pain through phosphorylation of Epac1 at Ser-108. Importantly, using the Epac inhibitor ESI-09, we validate Epac1 as a potential therapeutic target for chronic pain.
authors.affiliation: Laboratory of Neuroimmunology, Department of Symptom Research, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: Pooja
authors.initials: P
authors.lastname: Singhmar
authors.affiliation: Laboratory of Neuroimmunology, Department of Symptom Research, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: XiaoJiao
authors.initials: X
authors.lastname: Huo
authors.affiliation: Laboratory of Neuroimmunology and Developmental Origins of Disease, University Medical Center Utrecht, Utrecht 3584 EA, The Netherlands;
authors.forename: Niels
authors.initials: N
authors.lastname: Eijkelkamp
authors.affiliation: Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid 28049, Spain;
authors.forename: Susana Rojo
authors.initials: SR
authors.lastname: Berciano
authors.affiliation: Laboratory of Neuroimmunology, Department of Symptom Research, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: Faiza
authors.initials: F
authors.lastname: Baameur
authors.affiliation: Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, University of Texas Health Science Center, Houston, TX 77030;
authors.forename: Fang C
authors.initials: FC
authors.lastname: Mei
authors.affiliation: Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, University of Texas Health Science Center, Houston, TX 77030;
authors.forename: Yingmin
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Department of Integrative Biology and Pharmacology and Texas Therapeutics Institute, University of Texas Health Science Center, Houston, TX 77030;
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Translational Molecular Pathology, University of Texas MD Anderson Cancer Center, Houston, TX 77030.
authors.forename: David
authors.initials: D
authors.lastname: Hawke
authors.affiliation: Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid 28049, Spain;
authors.forename: Federico
authors.initials: F
authors.lastname: Mayor
authors.affiliation: Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid 28049, Spain;
authors.forename: Cristina
authors.initials: C
authors.lastname: Murga
authors.affiliation: Laboratory of Neuroimmunology, Department of Symptom Research, University of Texas MD Anderson Cancer Center, Houston, TX 77030;
authors.forename: Cobi J
authors.initials: CJ
authors.lastname: Heijnen
authors.affiliation: Laboratory of Neuroimmunology, Department of Symptom Research, University of Texas MD Anderson Cancer Center, Houston, TX 77030; akavelaars@mdanderson.org.
authors.forename: Annemieke
authors.initials: A
authors.lastname: Kavelaars
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002908:Chronic Disease; D005620:Freund's Adjuvant / Q000633:toxicity; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000502:physiology*; D005727:Ganglia, Spinal / Q000503:physiopathology; D020662:Guanine Nucleotide Exchange Factors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology*; D007249:Inflammation / Q000139:chemically induced / Q000150:complications*; D007473:Ion Channels / Q000502:physiology; D008465:Mechanoreceptors / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000502:physiology; D059225:Nociception / Q000502:physiology*; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D017288:Pain Threshold / Q000502:physiology; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D020827:rap1 GTP-Binding Proteins / Q000502:physiology
chemical_list: C482601:Epac protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D007473:Ion Channels; D009419:Nerve Tissue Proteins; C552921:Piezo2 protein, mouse; D010768:Phosphoserine; D005620:Freund's Adjuvant; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2; D020827:rap1 GTP-Binding Proteins
keywords: Epac1; Epac1 translocation; GRK2; Piezo2; chronic pain