title: EP4 receptor signalling in immature B cells involves cAMP and NF-κB dependent pathways.
abstract: OBJECTIVE
  Delineation of EP4 receptor signalling properties in immature B cells.
  
  
  METHODS
  WEHI 231 cells were used as a model of immature B lymphocytes. The effects of PGE2, EP4 receptor antagonist, EP4 receptor agonist, forskolin and adenylate cyclase inhibitor on proliferation of WEHI 231 cells were examined by MTS assay. Cyclic adenosine monophosphate (cAMP) levels were examined by ELISA, whereas phosphorylation of vasodilator-stimulated phosphoprotein (VASP), kinase, extracellular signal-regulated kinase1/2, IκB-α and nuclear factor (NF)-κB subunit p105 were subjected to Western blot analysis. Translocation of NF-κB subunit p65 and EPRAP (EP4 receptor associated protein) was examined by fluorescence microscopy. Levels of early growth response factor (Egr)-1 mRNA were determined by quantitative PCR.
  
  
  RESULTS
  We identified the EP4 receptor as the principal molecule mediating the growth-suppressive effect of prostaglandin E2 in WEHI 231 cells. EP4 receptor activation results in cAMP formation and the activation of protein kinase A, NF-κB1 p105 subunit stabilization and inhibition of IκBα phosphorylation, followed by the accumulation of NF-κB p65 subunit in the cell cytoplasm, whereas the activation of PI3K is not involved in EP4 receptor signalling. Elevation of cAMP and inhibition of NF-κB activation are two possible mechanisms by which the EP4 receptor inhibits the proliferation of immature B lymphocytes.
  
  
  CONCLUSIONS
  Modulation of the EP4 receptor on immature B lymphocytes provides important insight into the observed action of PGE2 and opens new possibilities for the development of therapies for autoimmune diseases, leukaemia and lymphomas.
authors: Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia.
authors: Matevz
authors: M
authors: Prijatelj
authors: Teja
authors: T
authors: Celhar
authors: Martina
authors: M
authors: Gobec
authors: Irena
authors: I
authors: Mlinaric-Rascan
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D020672:I-kappa B Proteins / Q000378:metabolism; D007154:Immune System Diseases / Q000188:drug therapy; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D054448:Precursor Cells, B-Lymphoid / Q000378:metabolism*; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D058309:Receptors, Prostaglandin E, EP4 Subtype; D000072000:NF-KappaB Inhibitor alpha; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015232:Dinoprostone