title: Differential p38 mitogen-activated protein kinase-controlled hypophosphorylation of the retinoblastoma protein induced by nitric oxide in neuroblastoma cells.
abstract: In this report we show that exogenous NO added to human neuroblastoma NB69 cells inhibits cell proliferation and downregulates the epidermal growth factor receptor (EGFR) and its downstream signaling pathways. These comprise the 3-phosphoinositide-dependent kinase 1/Akt/glycogen synthase kinase-3beta pathway, the mitogen-activated protein kinase (MAPK)/extracellular-regulated kinases 1 and 2 pathway, and the phospholipase Cgamma pathway. In contrast, NO enhances the EGFR-controlled p38MAPK pathway. We also show that NO enhances the activation of the cAMP-responsive element binding protein, a transcription factor controlled by p38MAPK, as demonstrated using 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole (SB202190), a p38MAPK inhibitor. These processes are accompanied by the NO-mediated hypophosphorylation of the retinoblastoma protein (pRb), preferentially at Ser795 compared to Ser780 and Ser807/811, and the downregulation of p27(KIP1), p21(CIP1/WAF1), and p16(INK4a), although NO downregulated p16(INK4a) only when the p38MAPK activity was suppressed. The p38MAPK pathway controls the phosphorylation status of pRb as SB202190 enhances the hypophosphorylation of pRb. We reverted the inhibitory action of NO on EGFR and pRb phosphorylation in living cells using cell-permeable reducing agents, which suggested that reversible S-nitrosation controls these proteins. Our results support the notion that NO negatively modulates the p38MAPK-controlled phosphorylation of pRb, inducing the subsequent arrest of the cell cycle at the G1/S transition.
authors.affiliation: Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Científicas, and Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Oscar
authors.initials: O
authors.lastname: González-Fernández
authors.forename: Amparo
authors.initials: A
authors.lastname: Jiménez
authors.forename: Antonio
authors.initials: A
authors.lastname: Villalobo
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D015536:Down-Regulation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D009447:Neuroblastoma; D009569:Nitric Oxide / Q000494:pharmacology / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D016160:Retinoblastoma Protein / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: C493956:CDKN1A protein, human; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D050759:Cyclin-Dependent Kinase Inhibitor p21; D007093:Imidazoles; D011725:Pyridines; D016160:Retinoblastoma Protein; D050760:Cyclin-Dependent Kinase Inhibitor p27; D009569:Nitric Oxide; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole