title: ERK signaling mediates CaSR-promoted axon growth.
abstract: The extracellular calcium-sensing receptor (CaSR) is a G-protein coupled receptor that monitors the systemic extracellular free ionized calcium level ([Ca(2+)]o) in organs involved in systemic [Ca(2+)]o homeostasis. CaSR is widely expressed in the nervous system and its activation promotes axon and dendrite growth during development, but the mechanism by which it does this is not known. Here we show that enhanced axon growth and branching from cultured embryonic sympathetic neurons by activation of the endogenous CaSR depends on the presence of nerve growth factor (NGF). Our observation that activation of overexpressed CaSR promotes axon growth in NGF-free medium has enabled us to investigate CaSR downstream signaling contributing to axon growth in the absence of NGF signaling. We show that activation of overexpressed CaSR leads to activation of ERK1 and ERK2, and pharmacological inhibition of CaSR-dependent ERK1/ERK2 activation prevents CaSR-dependent axon growth. Analysis of axon growth from cultured neurons expressing deletion mutants of the CaSR cytoplasmic tail revealed that the region between alanine 877 and glycine 907 is required for promoting axon growth that is distinct from the high-affinity filamin-A binding site that has previously been implicated in ERK1/ERK2 activation.
authors.affiliation: School of Biosciences, Biomedical Building, Museum Avenue, Cardiff CF10 3US, UK. Electronic address: thomas.vizard@ndcn.ox.ac.uk.
authors.forename: Thomas N
authors.initials: TN
authors.lastname: Vizard
authors.affiliation: School of Biosciences, Biomedical Building, Museum Avenue, Cardiff CF10 3US, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Newton
authors.affiliation: School of Biosciences, Biomedical Building, Museum Avenue, Cardiff CF10 3US, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Howard
authors.affiliation: School of Biosciences, Biomedical Building, Museum Avenue, Cardiff CF10 3US, UK.
authors.forename: Sean
authors.initials: S
authors.lastname: Wyatt
authors.affiliation: School of Biosciences, Biomedical Building, Museum Avenue, Cardiff CF10 3US, UK.
authors.forename: Alun M
authors.initials: AM
authors.lastname: Davies
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology*; D002460:Cell Line; D004789:Enzyme Activation; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D020932:Nerve Growth Factor / Q000378:metabolism; D044169:Receptors, Calcium-Sensing; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C577923:CASR protein, mouse; D044169:Receptors, Calcium-Sensing; D043562:Receptors, G-Protein-Coupled; D020932:Nerve Growth Factor; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3
keywords: Axon growth; Development; Extracellular calcium-sensing receptor; Extracellular-regulated kinase; Sympathetic neuron