title: CSK controls retinoic acid receptor (RAR) signaling: a RAR-c-SRC signaling axis is required for neuritogenic differentiation.
abstract: Herein, we report the first evidence that c-SRC is required for retinoic acid (RA) receptor (RAR) signaling, an observation that suggests a new paradigm for this family of nuclear hormone receptors. We observed that CSK negatively regulates RAR functions required for neuritogenic differentiation. CSK overexpression inhibited RA-mediated neurite outgrowth, a result which correlated with the inhibition of the SFK c-SRC. Consistent with an extranuclear effect of CSK on RAR signaling and neurite outgrowth, CSK overexpression blocked the downstream activation of RAC1. The conversion of GDP-RAC1 to GTP-RAC1 parallels the activation of c-SRC as early as 15 min following all-trans-retinoic acid treatment in LA-N-5 cells. The cytoplasmic colocalization of c-SRC and RARgamma was confirmed by immunofluorescence staining and confocal microscopy. A direct and ligand-dependent binding of RAR with SRC was observed by surface plasmon resonance, and coimmunoprecipitation studies confirmed the in vivo binding of RARgamma to c-SRC. Deletion of a proline-rich domain within RARgamma abrogated this interaction in vivo. CSK blocked the RAR-RA-dependent activation of SRC and neurite outgrowth in LA-N-5 cells. The results suggest that transcriptional signaling events mediated by RA-RAR are necessary but not sufficient to mediate complex differentiation in neuronal cells. We have elucidated a nongenomic extranuclear signal mediated by the RAR-SRC interaction that is negatively regulated by CSK and is required for RA-induced neuronal differentiation.
authors.affiliation: Section of Pediatric Hematology/Oncology, Department of Pediatrics, Aflac Cancer Center and Blood Disorders Services, Children's Healthcare of Atlanta, Emory University School of Medicine, Atlanta, GA 30022, USA.
authors.forename: Nandini
authors.initials: N
authors.lastname: Dey
authors.forename: Pradip K
authors.initials: PK
authors.lastname: De
authors.forename: Mu
authors.initials: M
authors.lastname: Wang
authors.forename: Hongying
authors.initials: H
authors.lastname: Zhang
authors.forename: Erika A
authors.initials: EA
authors.lastname: Dobrota
authors.forename: Kent A
authors.initials: KA
authors.lastname: Robertson
authors.forename: Donald L
authors.initials: DL
authors.lastname: Durden
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000378:metabolism; D016391:Genes, src; D006801:Humans; D016501:Neurites / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000378:metabolism; D011743:Pyrimidines / Q000378:metabolism; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D015398:Signal Transduction / Q000502:physiology*; D014212:Tretinoin / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; C000607071:RARA protein, human; C000607072:Rara protein, mouse; D018168:Receptors, Retinoic Acid; D011993:Recombinant Fusion Proteins; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin; C086603:Matk protein, mouse; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D020830:rac1 GTP-Binding Protein