1. Synaptic Drosophila UNC-13 is regulated by antagonistic G-protein pathways via a proteasome-dependent degradation mechanism.
- Author
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Aravamudan B and Broadie K
- Subjects
- Acetylcysteine pharmacology, Animals, Antibodies, Blotting, Western, Carrier Proteins, Colforsin pharmacology, Cyclic AMP-Dependent Protein Kinases drug effects, Cyclic AMP-Dependent Protein Kinases metabolism, Drosophila anatomy & histology, Drosophila Proteins drug effects, Drosophila Proteins metabolism, Drug Interactions, Enzyme Inhibitors pharmacology, Estrenes pharmacology, GTP-Binding Proteins antagonists & inhibitors, GTP-Binding Proteins classification, Horseradish Peroxidase metabolism, Immunohistochemistry, Indoles pharmacology, Insect Proteins metabolism, Maleimides pharmacology, Microscopy, Confocal instrumentation, Microscopy, Confocal methods, Mutation, Neomycin pharmacology, Neuromuscular Junction drug effects, Neuromuscular Junction metabolism, Oligopeptides pharmacology, Phorbol Esters pharmacology, Phospholipid Ethers pharmacology, Presynaptic Terminals classification, Presynaptic Terminals drug effects, Presynaptic Terminals metabolism, Proteasome Endopeptidase Complex, Pyrroles pharmacology, Pyrrolidinones pharmacology, Tumor Suppressor Proteins metabolism, Type C Phospholipases drug effects, Type C Phospholipases metabolism, Acetylcysteine analogs & derivatives, Caenorhabditis elegans Proteins, Carbazoles, Cysteine Endopeptidases metabolism, Drosophila metabolism, GTP-Binding Proteins metabolism, Helminth Proteins metabolism, Multienzyme Complexes metabolism, Synapses metabolism
- Abstract
UNC-13 is a highly conserved plasma membrane-associated synaptic protein implicated in the regulation of neurotransmitter release through the direct modulation of the SNARE exocytosis complex. Previously, we characterized the Drosophila homologue (DUNC-13) and showed it to be essential for neurotransmitter release immediately upstream of vesicular fusion ("priming") at the neuromuscular junction (NMJ). Here, we show that the abundance of DUNC-13 in NMJ synaptic boutons is regulated downstream of GalphaS and Galphaq pathways, which have inhibitory and facilitatory roles, respectively. Both cAMP modulation and PKA function are required for DUNC-13 synaptic up-regulation, suggesting that the cAMP pathway enhances synaptic efficacy via DUNC-13. Similarly, PLC function and DAG modulation also regulate the synaptic levels of DUNC-13, through a mechanism that appears independent of PKC. Our results suggest that proteasome-mediated protein degradation is the primary mechanism regulating DUNC-13 levels at the synapse. Both PLC- and PKA-mediated pathways appear to regulate synaptic levels of DUNC-13 through controlling the rate of proteasome-dependent DUNC-13 degradation. We conclude that the functional abundance of DUNC-13 at the synapse, a key determinant of synaptic vesicle priming and neurotransmitter release probability, is primarily regulated by the rate of protein degradation, rather than translocation or transport, convergently controlled via both cAMP and DAG signal transduction pathways., (Copyright 2003 Wiley Periodicals, Inc.)
- Published
- 2003
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