title: Prostanoid EP₁ receptors mediate up-regulation of the orphan nuclear receptor Nurr1 by cAMP-independent activation of protein kinase A, CREB and NF-κB.
abstract: OBJECTIVE
  Prostaglandin E(2) (PGE(2)) stimulation of the G protein-coupled prostanoid EP(1) receptor was found to up-regulate the expression of Nur-related factor 1 (Nurr1) (NR4A2), a transcription factor in the NR4A subfamily of nuclear receptors. The present studies characterize the molecular mechanism of this up-regulation.
  
  
  METHODS
  The expression of Nurr1 was examined by immunoblot analysis, the polymerase chain reaction and reporter gene assays in human embryonic kidney (HEK) cells stably expressing the recombinant EP(1) receptor and in SH-SY5Y neuroblastoma cells expressing endogenous EP(1) receptors. Signalling pathway inhibitors were used to examine the roles of Rho, PKA, the cAMP response element binding protein (CREB) and NF-κB on the PGE(2) stimulated up-regulation of Nurr1. CREB and NF-κB signalling were also examined by immunoblot analysis and reporter gene assays.
  
  
  RESULTS
  The EP(1) receptor mediated up-regulation of Nurr1 was blocked with inhibitors of Rho, PKA, NF-κB and CREB; but PGE(2) failed to significantly stimulate intracellular cAMP formation. PGE(2) stimulation of the EP1 receptor induced the phosphorylation and activation of CREB and NF-κB, which could be blocked by inhibition of PKA.
  
  
  CONCLUSIONS
  PGE(2) stimulation of the human EP(1) receptor up-regulates the expression of Nurr1 by a mechanism involving the sequential activation of the Rho, PKA, CREB and NF-κB signalling pathways. EP(1) receptors are implicated in tumorigenesis and the up-regulation of Nurr1 may underlie the anti-apoptotic effects of PGE(2) .
authors.affiliation: Department of Pharmacology & Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, USA.
authors.forename: R
authors.initials: R
authors.lastname: Ji
authors.forename: C M
authors.initials: CM
authors.lastname: Sanchez
authors.forename: C L
authors.initials: CL
authors.lastname: Chou
authors.forename: X B
authors.initials: XB
authors.lastname: Chen
authors.forename: D F
authors.initials: DF
authors.lastname: Woodward
authors.forename: J W
authors.initials: JW
authors.lastname: Regan
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004789:Enzyme Activation; D017930:Genes, Reporter; D005822:Genetic Vectors; D057809:HEK293 Cells; D006801:Humans; D049410:Luciferases, Renilla / Q000235:genetics; D016328:NF-kappa B / Q000378:metabolism*; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2 / Q000096:biosynthesis*; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000819:agonists* / Q000235:genetics; D014162:Transfection
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D016328:NF-kappa B; C539882:NR4A2 protein, human; D057126:Nuclear Receptor Subfamily 4, Group A, Member 2; D058306:Receptors, Prostaglandin E, EP1 Subtype; D000242:Cyclic AMP; D049410:Luciferases, Renilla; D017868:Cyclic AMP-Dependent Protein Kinases; D015232:Dinoprostone