title: Arrestins differentially regulate histamine- and oxytocin-evoked phospholipase C and mitogen-activated protein kinase signalling in myometrial cells.
abstract: OBJECTIVE
  The uterotonins oxytocin and histamine, mediate contractile signals through specific G protein-coupled receptors, a process which is tightly controlled during gestation to prevent preterm labour. We previously identified G protein-coupled receptor kinase (GRK)2 and GRK6 as respective cardinal negative regulators of histamine H(1) and oxytocin receptor signalling. GRK-mediated phosphorylation promotes arrestin recruitment, not only desensitizing receptors but activating an increasing number of diverse signalling pathways. Here we investigate potential roles that arrestins play in the regulation of myometrial oxytocin/histamine H(1) receptor signalling.
  
  
  METHODS
  Endogenous arrestins2 and 3 were specifically depleted using RNA-interference in a human myometrial cell line and the consequences of this for G protein-coupled receptor-mediated signalling were assessed using Ca(2+) /inositol 1,4,5-trisphophate imaging and standard mitogen-activated protein kinase (MAPK) assays.
  
  
  RESULTS
  Depletion of arrestin3, but not arrestin2 enhanced and prolonged H(1) receptor-stimulated Ca(2+) responses, whilst depletion of either arrestin increased oxytocin receptor responses. Arrestin3 depletion decreased H(1) receptor desensitization, whilst removal of either arrestin isoform was equally effective in preventing oxytocin receptor desensitization. Following arrestin3 depletion oxytocin-induced phospho-extracellular signal-regulated kinase1/2 signals were diminished and histamine-stimulated signals virtually absent, whereas depletion of arrestin2 augmented extracellular signal-regulated kinase1/2 responses to each agonist. Conversely, depletion of arrestin3 enhanced p38 signals to each agonist, whilst arrestin2 suppression increased oxytocin-, but not histamine-induced p38 MAPK responses.
  
  
  CONCLUSIONS
  Arrestin proteins are key regulators of H(1) and oxytocin receptor desensitization, and play integral roles mediating uterotonin-stimulated MAPK-signalling. These data provide insights into the in situ regulation of these receptor subtypes and may inform pathophysiological functioning in preterm labour.
authors.affiliation: Endocannabinoid Research Group, Reproductive Sciences Section, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester Royal Infirmary, Leicester, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Brighton
authors.forename: Shashi
authors.initials: S
authors.lastname: Rana
authors.forename: Ra John
authors.initials: RJ
authors.lastname: Challiss
authors.forename: Justin C
authors.initials: JC
authors.lastname: Konje
authors.forename: Jonathon M
authors.initials: JM
authors.lastname: Willets
mesh_terms: D019390:Arrestins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005260:Female; D006632:Histamine / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009215:Myometrium / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D020033:Protein Isoforms; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000235:genetics; D011969:Receptors, Histamine H1 / Q000378:metabolism; D018045:Receptors, Oxytocin / Q000378:metabolism; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D019390:Arrestins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011969:Receptors, Histamine H1; D018045:Receptors, Oxytocin; D010121:Oxytocin; D006632:Histamine; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D002118:Calcium