title: Rapid activity-dependent delivery of the neurotrophic protein CPG15 to the axon surface of neurons in intact Xenopus tadpoles.
abstract: CPG15 (aka neuritin) is an activity-induced GPI-anchored axonal protein that promotes dendritic and axonal growth, and accelerates synaptic maturation in vivo. Here we show that CPG15 is distributed inside axons and on the axon surface. CPG15 is trafficked to and from the axonal surface by membrane depolarization. To assess CPG15 trafficking in vivo, we expressed an ecliptic pHluorin (EP)-CPG15 fusion protein in optic tectal explants and in retinal ganglion cells of intact Xenopus tadpoles. Depolarization by KCl increased EP-CPG15 fluorescence on axons. Intraocular kainic acid (KA) injection rapidly increased cell-surface EP-CPG15 in retinotectal axons, but coinjection of TTX and KA did not. Consistent with this, we find that intracellular CPG15 is localized to vesicles and endosomes in presynaptic terminals and colocalizes with synaptic vesicle proteins. The results indicate that the delivery of the neurotrophic protein CPG15 to the axon surface can be regulated on a rapid time scale by activity-dependent mechanisms in vivo.
authors.affiliation: Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
authors.forename: Isabel
authors.initials: I
authors.lastname: Cantallops
authors.forename: Hollis T
authors.initials: HT
authors.lastname: Cline
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D007608:Kainic Acid / Q000494:pharmacology; D007814:Larva; D008565:Membrane Proteins / Q000378:metabolism*; D008845:Microinjections; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology*; D009924:Organ Culture Techniques; D011189:Potassium Chloride / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013477:Superior Colliculi / Q000166:cytology; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014981:Xenopus
chemical_list: D000779:Anesthetics, Local; D018690:Excitatory Amino Acid Agonists; C073804:FM1 43; D008565:Membrane Proteins; C484390:NRN1 protein, Xenopus; D009419:Nerve Tissue Proteins; C485187:PHluorin; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D049452:Green Fluorescent Proteins; D013779:Tetrodotoxin; D011189:Potassium Chloride; D007608:Kainic Acid