title: Axonal cap-dependent translation regulates presynaptic p35.
abstract: Axonal growth cones synthesize proteins during development and in response to injury in adult animals. Proteins locally translated in axons are used to generate appropriate responses to guidance cues, contribute to axon growth, and can serve as retrograde messengers. In addition to growth cones, mRNAs and translational machinery are also found along the lengths of axons where synapses form en passant, but contributions of intra-axonal translation to developing synapses are poorly understood. Here, we engineered a subcellular-targeting translational repressor to inhibit mRNA translation in axons, and we used this strategy to investigate presynaptic contributions of cap-dependent protein translation to developing CNS synapses. Our data show that intra-axonal mRNA translation restrains synaptic vesicle recycling pool size and that one target of this regulation is p35, a Cdk5 activating protein. Cdk5/p35 signaling regulates the size of vesicle recycling pools, p35 levels diminish when cap-dependent translation is repressed, and restoring p35 levels rescues vesicle recycling pools from the effects of spatially targeted translation repression. Together our findings show that intra-axonal synthesis of p35 is required for normal vesicle recycling in developing neurons, and that targeted translational repression provides a novel strategy to investigate extrasomal protein synthesis in neurons.
authors.affiliation: Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine and Graduate School of Biomedical Sciences at Mount Sinai, New York, New York, 10029.
authors.forename: Kuangfu
authors.initials: K
authors.lastname: Hsiao
authors.forename: Ozlem
authors.initials: O
authors.lastname: Bozdagi
authors.forename: Deanna L
authors.initials: DL
authors.lastname: Benson
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism; D020439:Growth Cones / Q000378:metabolism; D006624:Hippocampus / Q000196:embryology / Q000378:metabolism; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D061848:Optical Imaging; D017729:Presynaptic Terminals / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats
chemical_list: D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C089495:neuronal Cdk5 activator (p25-p35); D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat
keywords: Cdk5; cap-dependent translation; mRNA transport; targeted repression; vesicle recycling