title: Differential phosphorylation of Smad1 integrates BMP and neurotrophin pathways through Erk/Dusp in axon development.
abstract: Sensory axon development requires concerted actions of growth factors for the precise control of axonal outgrowth and target innervation. How developing sensory neurons integrate different cues is poorly understood. We demonstrate here that Smad1 activation is required for neurotrophin-mediated sensory axon growth in vitro and in vivo. Through differential phosphorylation, Smad1 exerts transcriptional selectivity to regulate the expression and activity of Erk1 and Erk2-two key neurotrophin effectors. Specifically, bone morphogenetic proteins (BMPs) signal through carboxy-terminal phosphorylation of Smad1 (pSmad1C) to induce Erk1/2 transcription for enhanced neurotrophin responsiveness. Meanwhile, neurotrophin signaling results in linker phosphorylation of Smad1 (pSmad1L), which in turn upregulates an Erk-specific dual-specificity phosphatase, Dusp6, leading to reduced pErk1/2 and constituting a negative-feedback loop for the prevention of axon overgrowth. Together, the BMP and neurotrophin pathways form a tightly regulated signaling network with a balanced ratio of Erk1/2 and pErk1/2 to direct the precise connections between sensory neurons and peripheral targets.
authors.affiliation: Fishberg Department of Neuroscience, Friedman Brain Institute, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Mattéa J
authors.initials: MJ
authors.lastname: Finelli
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Murphy
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zou
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D054637:Dual-Specificity Phosphatases / Q000378:metabolism*; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D020933:Neurotrophin 3 / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011984:Sensory Receptor Cells / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051898:Smad1 Protein / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D019485:Bone Morphogenetic Proteins; D020933:Neurotrophin 3; D051898:Smad1 Protein; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D054637:Dual-Specificity Phosphatases