title: Repression of Ca2+/calmodulin-dependent protein kinase IV signaling accelerates retinoic acid-induced differentiation of human neuroblastoma cells.
abstract: Neuroblastoma cells having stem cell-like qualities are widely employed models for the study of neural stem/progenitor cell proliferation and differentiation. We find that human BE(2)C neuroblastoma cells possess a signaling cascade initiated by Ca(2+) influx via voltage-dependent calcium channels and the N-methyl-D-aspartate (NMDA) receptor and culminating in nuclear calmodulin-dependent protein kinase IV (CaMKIV)-mediated phosphorylation and activation of the transcription factors Ca(2+)/cyclic AMP-response element-binding protein (CREB) and ATF1 (activating transcription factor-1). This pathway functions to maintain BE(2)C cells in an undifferentiated, proliferative state. Parallel to this Ca(2+)-dependent pathway is a hormone-responsive program by which retinoic acid (RA) initiates the differentiation of BE(2)C cells toward a neuronal lineage. This is evidenced by RA-dependent induction of the cell cycle inhibitor p21/Cip1 (Cdk-interacting protein 1) and cell cycle arrest, induction of the neuroblastic marker doublecortin and of the neuron-specific intermediate filament protein, peripherin, and by RA-stimulated extension of neuritic processes. During neuronal differentiation there is a complex antagonistic interplay between these two major signaling pathways. RA down-regulates expression of CaMKIV and one of its upstream activators, CaMKK1 (calmodulin-dependent protein kinase kinase 1). This is accompanied by RA-induced suppression of activating phosphorylation of CREB with a time course paralleling that of CaMKIV down-regulation. RA-induced repression of the Ca(2+)/calmodulin-dependent protein kinase kinase/CaMKIV/CREB pathway appears to be involved in regulating the timing of neuronal differentiation, as shown by the effect of RNA interference of CaMKIV to markedly accelerate RA-dependent up-regulation of p21/Cip1 and doublecortin expression and RA-promoted neurite outgrowth. RA-induced repression of the CaMKIV signaling pathway may represent an early event in retinoid-dependent neuronal differentiation.
authors.affiliation: Department of Pharmacology and Toxicology, State University of New York, Buffalo, New York 14214, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Feliciano
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Edelman
mesh_terms: D051697:Activating Transcription Factor 1 / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4 / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D000089622:Doublecortin Domain Proteins; D006801:Humans; D015151:Immunoblotting; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: C531110:ATF1 protein, human; D051697:Activating Transcription Factor 1; D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D050759:Cyclin-Dependent Kinase Inhibitor p21; D000089622:Doublecortin Domain Proteins; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides; D014212:Tretinoin; C517683:CAMK4 protein, human; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D002118:Calcium