Dok-4 regulates GDNF-dependent neurite outgrowth through downstream activation of Rap1 and mitogen-activated protein kinase.

Abstract

During development of the central and peripheral nervous systems, neurite extension mediated via glial-cell-line-derived neurotrophic factor (GDNF) and its receptor RET is critical for neuronal differentiation. In the present study, we investigated the role of the RET substrate Dok-4 in neurite outgrowth induced by the GDNF/RET signaling pathway. In TGW neuroblastoma cells, which endogenously express both RET and Dok-4, depletion of Dok-4 through treatment with small interfering RNA resulted in a marked decrease in GDNF-stimulated neurite outgrowth. By contrast, exogenous expression of wild-type Dok-4 induced sustained p44/42 mitogen-activated protein kinase (ERK1/2) activation and enhanced neurite outgrowth. Expression of Dok-4 mutants in which the tyrosine residues at codons 187, 220 and 270, conserved between Dok-4, -5, and -6, were each replaced with a phenylalanine inhibited sustained ERK1/2 activation and neurite outgrowth. We also found that Dok-4 induced a significant activation of the small G protein Rap1 and that expression of a dominant active Rap1 mutant restored neurite outgrowth in Dok-4-depleted cells. By contrast, expression of a dominant negative Rap1 mutant impaired GDNF-stimulated neurite outgrowth from TGW cells. Finally, we found that neurite formation in cultured rat hippocampal neurons was enhanced by the expression of Dok-4. Together, our results suggest that Dok-4, through activation of the Rap1-ERK1/2 pathway, regulates GDNF-mediated neurite outgrowth during neuronal development.

• Authors: Mayumi Uchida, Atsushi Enomoto, Toshifumi Fukuda, Kei Kurokawa, Kengo Maeda, Yoshinori Kodama, Naoya Asai, Taisaku Hasegawa, Yohei Shimono, Mayumi Jijiwa, Masatoshi Ichihara, Yoshiki Murakumo, Masahide Takahashi
• Journal: Journal of cell science (J Cell Sci) Vol. 119 Issue Pt 15 Pg. 3067-77 (Aug 01 2006) ISSN: 0021-9533 [Print] England
• PMID: 16820412 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adaptor Proteins, Signal Transducing
• DOK4 protein, human
• Dok4 protein, mouse
• Glial Cell Line-Derived Neurotrophic Factor
• Intracellular Signaling Peptides and Proteins
• Phosphoproteins
• Proto-Oncogene Proteins c-ret
• Proto-Oncogene Proteins c-akt
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• rap1 GTP-Binding Proteins

Topics

• Adaptor Proteins, Signal Transducing (genetics, metabolism)
• Amino Acid Sequence
• Animals
• Cell Line, Tumor
• Cells, Cultured
• Enzyme Activation
• Glial Cell Line-Derived Neurotrophic Factor (metabolism)
• Hippocampus (cytology)
• Humans
• Intracellular Signaling Peptides and Proteins (genetics, metabolism)
• Mice
• Mitogen-Activated Protein Kinase 1 (genetics, metabolism)
• Mitogen-Activated Protein Kinase 3 (genetics, metabolism)
• Molecular Sequence Data
• Neurites (metabolism, ultrastructure)
• Neurons (cytology, metabolism)
• Phosphoproteins (genetics, metabolism)
• Proto-Oncogene Proteins c-akt (metabolism)
• Proto-Oncogene Proteins c-ret (genetics, metabolism)
• RNA Interference
• Rats
• Rats, Sprague-Dawley
• Sequence Alignment
• Signal Transduction (physiology)
• rap1 GTP-Binding Proteins (genetics, metabolism)