Abstract
Synaptic vesicles (SVs) are retrieved by more than one mode in central nerve terminals. During mild stimulation, the dominant SV retrieval pathway is classical clathrin-mediated endocytosis (CME). During elevated neuronal activity, activity-dependent bulk endocytosis (ADBE) predominates, which requires activation of the calcium-dependent protein phosphatase calcineurin. We now report that calcineurin dephosphorylates dynamin I in nerve terminals only above the same activity threshold that triggers ADBE. ADBE was arrested when the two major phospho-sites on dynamin I were perturbed, suggesting that dynamin I dephosphorylation is a key step in its activation. Dynamin I dephosphorylation stimulates a specific dynamin I-syndapin I interaction. Inhibition of this interaction by competitive peptides or by site-directed mutagenesis exclusively inhibited ADBE but did not affect CME. The results reveal that the phospho-dependent dynamin-syndapin interaction recruits ADBE to massively increase SV endocytosis under conditions of elevated neuronal activity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Action Potentials / physiology
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Analysis of Variance
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Animals
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Animals, Newborn
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Calcineurin / metabolism
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Calcium / metabolism
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Carrier Proteins / antagonists & inhibitors
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Carrier Proteins / chemistry
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Cells, Cultured
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Cerebellum / cytology
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Cytoskeletal Proteins
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Dextrans / metabolism
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Dynamin I / chemistry
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Dynamin I / genetics
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Dynamin I / metabolism*
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Electric Stimulation / methods
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Endocytosis / drug effects
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Endocytosis / physiology*
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GTP Phosphohydrolases / metabolism
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Horseradish Peroxidase / metabolism
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Hydrazones / pharmacology
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Microscopy, Immunoelectron / methods
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Mutagenesis, Site-Directed / methods
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Neural Inhibition / physiology
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Neurons / cytology*
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Neurons / drug effects
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Oligonucleotides / pharmacology
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Phosphorylation / drug effects
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Phosphorylation / physiology
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Potassium Chloride / pharmacology
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Rats
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Rats, Sprague-Dawley
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Serine / metabolism
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Synaptic Vesicles / drug effects
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Synaptic Vesicles / physiology*
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Synaptic Vesicles / ultrastructure
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Synaptophysin / metabolism
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Time Factors
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Transfection / methods
Substances
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Carrier Proteins
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Cytoskeletal Proteins
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Dextrans
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Hydrazones
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N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide
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Oligonucleotides
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Pacsin1 protein, rat
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Synaptophysin
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Serine
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Potassium Chloride
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Horseradish Peroxidase
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Calcineurin
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Dynamin I
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GTP Phosphohydrolases
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Calcium