TY - JOUR
T1 - Wild-type monomeric α-synuclein can impair vesicle endocytosis and synaptic fidelity via tubulin polymerization at the calyx of held
AU - Eguchi, Kohgaku
AU - Taoufiq, Zacharie
AU - Thorn-Seshold, Oliver
AU - Trauner, Dirk
AU - Hasegawa, Masato
AU - Takahashi, Tomoyuki
N1 - Funding Information:
This work was supported by the Okinawa Institute of Science and Technology, the Core Research for Evolutionary Scienceand Technology of the Japan Science and Technology Agency (T.T.), and the Japan Society for the Promotion of Science (Grant-in-Aid for Young Scientists to K.E.). We thank Yasuo Ihara and Takeshi Sakaba for comments and Steven Aird for editing this manuscript.
Publisher Copyright:
© 2017 the authors.
PY - 2017/6/21
Y1 - 2017/6/21
N2 - α-Synuclein is a presynaptic protein the function of which has yet to be identified, but its neuronal content increases in patients of synucleinopathies including Parkinson's disease. Chronic overexpression of α-synuclein reportedly expresses various phenotypes of synaptic dysfunction, but the primary target of its toxicity has not been determined. To investigate this, we acutely loaded human recombinant α-synuclein or its pathological mutants in their monomeric forms into the calyces of Held presynaptic terminals in slices from auditorily mature and immature rats of either sex. Membrane capacitance measurements revealed significant and specific inhibitory effects of WT monomeric α-synuclein on vesicle endocytosis throughout development. However, the α-synuclein A53T mutant affected vesicle endocytosis only at immature calyces, whereas the A30P mutant had no effect throughout. The endocytic impairment by WT α-synuclein was rescued by intraterminal coloading of the microtubule (MT) polymerization blocker nocodazole. Furthermore, it was reversibly rescued by presynaptically loaded photostatin-1, a photoswitcheable inhibitor of MT polymerization, in a light-wavelength-dependent manner. In contrast, endocytic inhibition by the A53T mutant at immature calyces was not rescued by nocodazole. Functionally, presynaptically loaded WT α-synuclein had no effect on basal synaptic transmission evoked at a low frequency, but significantly attenuated exocytosis and impaired the fidelity of neurotransmission during prolonged high-frequency stimulation. We conclude that monomeric WT α-synuclein primarily inhibits vesicle endocytosis via MT overassembly, thereby impairing high-frequency neurotransmission.
SIGNIFICANCE STATEMENT Abnormal α-synuclein abundance is associated with synucleinopathies including Parkinson's disease, but neither the primary target of α-synuclein toxicity nor its mechanism is identified. Here, we loaded monomeric α-synuclein directly into mammalian glutamatergic nerve terminals and found that it primarily inhibits vesicle endocytosis and subsequently impairs exocytosis and neurotransmission fidelity during prolonged high-frequency stimulation. Such α-synuclein toxicity could be rescued by blocking microtubule polymerization, suggesting that microtubule overassembly underlies the toxicity of acutely elevated α-synuclein in the nerve terminal.
AB - α-Synuclein is a presynaptic protein the function of which has yet to be identified, but its neuronal content increases in patients of synucleinopathies including Parkinson's disease. Chronic overexpression of α-synuclein reportedly expresses various phenotypes of synaptic dysfunction, but the primary target of its toxicity has not been determined. To investigate this, we acutely loaded human recombinant α-synuclein or its pathological mutants in their monomeric forms into the calyces of Held presynaptic terminals in slices from auditorily mature and immature rats of either sex. Membrane capacitance measurements revealed significant and specific inhibitory effects of WT monomeric α-synuclein on vesicle endocytosis throughout development. However, the α-synuclein A53T mutant affected vesicle endocytosis only at immature calyces, whereas the A30P mutant had no effect throughout. The endocytic impairment by WT α-synuclein was rescued by intraterminal coloading of the microtubule (MT) polymerization blocker nocodazole. Furthermore, it was reversibly rescued by presynaptically loaded photostatin-1, a photoswitcheable inhibitor of MT polymerization, in a light-wavelength-dependent manner. In contrast, endocytic inhibition by the A53T mutant at immature calyces was not rescued by nocodazole. Functionally, presynaptically loaded WT α-synuclein had no effect on basal synaptic transmission evoked at a low frequency, but significantly attenuated exocytosis and impaired the fidelity of neurotransmission during prolonged high-frequency stimulation. We conclude that monomeric WT α-synuclein primarily inhibits vesicle endocytosis via MT overassembly, thereby impairing high-frequency neurotransmission.
SIGNIFICANCE STATEMENT Abnormal α-synuclein abundance is associated with synucleinopathies including Parkinson's disease, but neither the primary target of α-synuclein toxicity nor its mechanism is identified. Here, we loaded monomeric α-synuclein directly into mammalian glutamatergic nerve terminals and found that it primarily inhibits vesicle endocytosis and subsequently impairs exocytosis and neurotransmission fidelity during prolonged high-frequency stimulation. Such α-synuclein toxicity could be rescued by blocking microtubule polymerization, suggesting that microtubule overassembly underlies the toxicity of acutely elevated α-synuclein in the nerve terminal.
KW - Alpha-synuclein
KW - Calyx of Held
KW - Microtubules
KW - Synaptic transmission
KW - Vesicle endocytosis
KW - Exocytosis/drug effects
KW - Rats, Wistar
KW - Mutation/genetics
KW - Humans
KW - Recombinant Proteins/genetics
KW - Synaptic Vesicles/drug effects
KW - Polymerization
KW - Rats
KW - Tubulin/metabolism
KW - Auditory Pathways/drug effects
KW - Male
KW - Nocodazole/pharmacology
KW - Synapses/drug effects
KW - Endocytosis/drug effects
KW - Animals
KW - alpha-Synuclein/genetics
KW - Synaptic Transmission/drug effects
KW - Female
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U2 - 10.1523/JNEUROSCI.0179-17.2017
DO - 10.1523/JNEUROSCI.0179-17.2017
M3 - Article
C2 - 28576942
AN - SCOPUS:85021162205
SN - 0270-6474
VL - 37
SP - 6043
EP - 6052
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 25
ER -