Molecular dissection of TrkA signal transduction pathways mediating differentiation in human neuroblastoma cells

• Published in: Oncogene Vol. 19; no. 16; pp. 2043 - 2051
• Main Authors: EGGERT, A, IKEGAKI, N, LIU, X.-G, CHOU, T. T, LEE, V. M, TROJANOWSKI, J. Q, BRODEUR, G. M
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing 13.04.2000; Nature Publishing Group
• Subjects: Adaptor Proteins, Signal Transducing; Biological and medical sciences; Carrier Proteins - drug effects; Carrier Proteins - metabolism; Cell activation; Cell differentiation; Cell Differentiation - drug effects; Cell proliferation; Chromones - pharmacology; DNA-Binding Proteins - drug effects; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Early Growth Response Protein 1; Enzyme Inhibitors - pharmacology; Flavonoids - pharmacology; Gene expression; Gene Expression Regulation, Neoplastic; Genes, Immediate-Early; Humans; Immediate-Early Proteins; Isoenzymes - drug effects; Isoenzymes - genetics; Isoenzymes - metabolism; Kinases; MAP kinase; Medical sciences; Mitogen-Activated Protein Kinases - drug effects; Mitogen-Activated Protein Kinases - metabolism; Morpholines - pharmacology; mRNA; Mutation; Nerve growth factor; Nerve Growth Factor - metabolism; Nerve Growth Factor - pharmacology; Neuroblastoma; Neuroblastoma - drug therapy; Neuroblastoma - metabolism; Neuroblastoma - pathology; Neuroblastoma cells; Neurology; neurothropin receptors; Pheochromocytoma cells; Phospholipase C gamma; Phosphorylation; Protein kinase; ras Proteins - genetics; ras Proteins - metabolism; Receptor, trkA - drug effects; Receptor, trkA - genetics; Receptor, trkA - metabolism; Signal Transduction; Transcription Factors - drug effects; Transcription Factors - genetics; Transcription Factors - metabolism; Transfection; TrkA protein; TrkA receptors; Tumor Cells, Cultured; Tumors of the nervous system. Phacomatoses; Type C Phospholipases - drug effects; Type C Phospholipases - genetics; Type C Phospholipases - metabolism; Human; Neurotrophin; Autophosphorylation; Nervous system diseases; Enzyme; Ligand; Transferases; Nerve growth factor; Malignant tumor; Neuroblastoma; Sympathetic nervous system; Cell differentiation; Gene expression; Genetic transfer; Signal transduction; Cell line; C-Onc gene; Mutation; Protein-tyrosine kinase; Biological receptor
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/sj.onc.1203518

Activation of the neurotrophin receptor TrkA by its ligand nerve growth factor (NGF) initiates a cascade of signaling events leading to neuronal differentiation in vitro and might play an important role in the differentiation of favorable neuroblastomas (NB) in vivo. To study TrkA signal transduction pathways and their effects on differentiation in NB, we stably expressed wild-type TrkA and five different TrkA mutants in the NGF unresponsive human NB cell line SH-SY5Y. Resulting clones were characterized by TrkA mRNA and protein expression, and by autophosphorylation of the receptor. Introduction of wild-type TrkA restored NGF responsiveness of SH-SY5Y cells, as demonstrated by morphological differentiation, activation of mitogen-activated protein kinases (MAPK) and induction of immediate-early genes. Expression of TrkA in the absence of NGF resulted in growth inhibition of transfectants compared to parental cells, whereas NGF-treatment increased their proliferation rate. Analysis of downstream signal transduction pathways indicated that NGF-induced differentiation was dependent on TrkA kinase activity. Our data suggest that several redundant pathways are present further downstream, but activation of the RAS/MAPK signaling pathway seems to be of major importance for NGF mediated differentiation of NB cells. Our results also show that the signaling effector SH2-B is a substrate of NGF-mediated Trk signaling in NB, whereas it is not activated by NGF in rat pheochromocytoma PC12 cells. This might explain the differences we observed in TrkA signaling between neuroblastoma and PC12 cells. Further insight into TrkA signaling may suggest new options for the treatment of NB.