Abstract
A neuron forms thousands of presynaptic nerve terminals on its axons, far removed from the cell body. The protein CSPα resides in presynaptic terminals, where it forms a chaperone complex with Hsc70 and SGT. Deletion of CSPα results in massive neurodegeneration that impairs survival in mice and flies. In CSPα-knockout mice, levels of presynaptic SNARE complexes and the SNARE protein SNAP-25 are reduced, suggesting that CSPα may chaperone SNARE proteins, which catalyse synaptic vesicle fusion. Here, we show that the CSPα-Hsc70-SGT complex binds directly to monomeric SNAP-25 to prevent its aggregation, enabling SNARE-complex formation. Deletion of CSPα produces an abnormal SNAP-25 conformer that inhibits SNARE-complex formation, and is subject to ubiquitylation and proteasomal degradation. Even in wild-type mouse terminals, SNAP-25 degradation is regulated by synaptic activity; this degradation is decreased by CSPα overexpression, and enhanced by CSPα deletion. Thus, SNAP-25 function is maintained during rapid SNARE cycles by equilibrium between CSPα-dependent chaperoning and ubiquitin-dependent degradation, revealing unique protein quality-control machinery within the presynaptic compartment.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Brain / metabolism
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Cells, Cultured
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Female
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HEK293 Cells
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HSC70 Heat-Shock Proteins / metabolism
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HSP40 Heat-Shock Proteins / genetics
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HSP40 Heat-Shock Proteins / metabolism
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HSP40 Heat-Shock Proteins / physiology*
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Humans
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Immunoblotting
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Male
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Membrane Proteins / physiology*
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Mice
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Mice, Knockout
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Mice, Transgenic
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Molecular Chaperones / genetics
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Molecular Chaperones / metabolism
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Neurons / cytology
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Neurons / metabolism
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Neurons / physiology
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Proteasome Endopeptidase Complex / metabolism
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Protein Binding
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Rats
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Reverse Transcriptase Polymerase Chain Reaction
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SNARE Proteins / genetics
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SNARE Proteins / metabolism*
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Synaptic Transmission / physiology*
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Synaptosomal-Associated Protein 25 / genetics
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Synaptosomal-Associated Protein 25 / metabolism*
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Temperature
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Ubiquitination
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alpha-Synuclein / genetics
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alpha-Synuclein / metabolism
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alpha-Synuclein / physiology
Substances
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HSC70 Heat-Shock Proteins
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HSP40 Heat-Shock Proteins
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Hspa8 protein, mouse
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Membrane Proteins
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Molecular Chaperones
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SNARE Proteins
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Snap25 protein, mouse
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Synaptosomal-Associated Protein 25
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alpha-Synuclein
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cysteine string protein
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Proteasome Endopeptidase Complex