Objective: 1. What is the endogenous form of ⍺-Synuclein in various cell types?
2. How do WT ⍺-Synuclein monomer and aggregates affect presynaptic membrane fusion and the underlying machinery? How do they affect the above differentially from those of fPD mutants?
Background: ⍺-Synuclein is an IDP whose pathology underlies various neurodegenerative diseases. Its cytotoxicity is due to the formation of inclusion bodies containing different aggregates of the protein. Endogenous ⍺-Synuclein too populates the cell as different oligomeric forms as seen in some cell types. This raises questions regarding the switch from endogenous to pathological oligomers in disease conditions and the effects on various functions of the protein, especially presynaptic ones.
Method: 1. In-vitro SNARE reconstituted systems like Liposomes and Nanodiscs to study the effect of WT and fPD ⍺-Synuclein monomers and Calcium (Ca2+) induced aggregates on different aspects of membrane fusion like rate of SNARE complex formation, rate of membrane fusion, etc., and their respective toxicities.
2. Primary and secondary cultures of Cortical neurons, HEK293T and PC12 cell lines, coupled with Immunoprecipitation and Western Blotting.
Results: 1. WT aggregates incubated with Sulforhodamine-B (SRB) entrapped liposomes showed an increase in the extent of dye leakage due to aggregates formed post 7 hours of aggregation. The same was observed for three fPD aggregates from as early as 2 hours post aggregation.
2. WT and fPD aggregates hamper SNARE complex assembly in a time dependent manner, and also hamper the rate and extent of SNARE mediated membrane fusion in a concentration and time dependent manner (E46K mutation showing the most severe effects).
3. WT ⍺-Synuclein populates as primarily oligomers in PC12 and cortical neurons, but as monomers in HEK293T cells.
Conclusion: 1. Increased dye leakage caused by the aggregates indicate a mechanism of toxicity by membrane permeabilization.
2. Pathological forms of ⍺-Synuclein (monomers or aggregates) hamper different processes associated with presynaptic membrane fusion, and the severity of the effects can be correlated to membrane affinity (as seen for E46K ⍺-Synuclein).
3. ⍺-Synuclein populates as oligomers in cell types where it endogenously present and as monomers in an overexpression system, presumably due to certain PTMs on the protein that can facilitate and stabilize oligomeric forms of the protein.
References: 1. Nellikka RK, Bhaskar BR, Sanghrajka K, Patil SS, Das D. α-Synuclein kinetically regulates the nascent fusion pore dynamics. Proc Natl Acad Sci U S A. 2021 Aug 24;118(34):e2021742118. doi: 10.1073/pnas.2021742118. PMID: 34413185; PMCID: PMC8403915.
2. Bartels T, Choi JG, Selkoe DJ. α-Synuclein occurs physiologically as a helically folded tetramer that resists aggregation. Nature. 2011 Aug 14;477(7362):107-10. doi: 10.1038/nature10324. PMID: 21841800; PMCID: PMC3166366.
3. Burré J, Sharma M, Tsetsenis T, Buchman V, Etherton MR, Südhof TC. Alpha-synuclein promotes SNARE-complex assembly in vivo and in vitro. Science. 2010 Sep 24;329(5999):1663-7. doi: 10.1126/science.1195227. Epub 2010 Aug 26. PMID: 20798282; PMCID: PMC3235365.
To cite this abstract in AMA style:
M. Sriram, D. Rege, A. Das, R. Nellikka, D. Das. Aggregation – Dependent Effects of Wild-Type and Mutant α-Synuclein on Synaptic Membrane Fusion [abstract]. Mov Disord. 2026; 41 (suppl 1). https://www.mdsabstracts.org/abstract/aggregation-dependent-effects-of-wild-type-and-mutant-%ce%b1-synuclein-on-synaptic-membrane-fusion/. Accessed October 1, 2026.« Back to 2026 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/aggregation-dependent-effects-of-wild-type-and-mutant-%ce%b1-synuclein-on-synaptic-membrane-fusion/