title: Nonclassical action of retinoic acid on the activation of the cAMP response element-binding protein in normal human bronchial epithelial cells.
abstract: Vitamin A (retinol) is essential for normal regulation of cell growth and differentiation. We have shown that the retinol metabolite retinoic acid (RA) induces mucous cell differentiation of normal human tracheobronchial epithelial (NHTBE) cells. However, early biological effects of RA in the differentiation of bronchial epithelia are largely unknown. Here, we showed that RA rapidly activated cAMP response element-binding protein (CREB). However, RA did not use the conventional retinoic acid receptor (RAR)/retinoid X receptor (RXR) to activate CREB. RA activated CREB in NHTBE and H1734 cells in which RARs/RXR were silenced with small interfering RNA (siRNA) targeting RAR/RXR expression or deactivated by antagonist. Inhibition of protein kinase C (PKC) or extracellular regulated kinase (ERK1/2) blocked the RA-mediated activation of CREB. In addition, depletion of p90 ribosomal S6 kinase (RSK) via siRSK1/2 completely abolished the activation, suggesting that PKC, ERK, and RSK are required for the activation. Altogether, this study provides the first evidence that RA rapidly activates CREB transcription factor via PKC, ERK, and RSK in a retinoid receptor-independent manner in normal bronchial epithelial cells. This noncanonical RA signaling pathway may play an important role in mediating early biological effects in the mucociliary differentiation of bronchial epithelia.
authors.affiliation: Department of Thoracic/Head and Neck Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Sita
authors.initials: S
authors.lastname: Aggarwal
authors.forename: Seung-Wook
authors.initials: SW
authors.lastname: Kim
authors.forename: Kyounga
authors.initials: K
authors.lastname: Cheon
authors.forename: Fazal H
authors.initials: FH
authors.lastname: Tabassam
authors.forename: Joo-Heon
authors.initials: JH
authors.lastname: Yoon
authors.forename: Ja Seok
authors.initials: JS
authors.lastname: Koo
mesh_terms: D001980:Bronchi / Q000166:cytology / Q000378:metabolism*; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000502:physiology; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction; D015533:Transcriptional Activation; D014212:Tretinoin / Q000494:pharmacology / Q000502:physiology*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D047488:Retinoid X Receptors; D014212:Tretinoin; D011494:Protein Kinases; D019893:Ribosomal Protein S6 Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases