Synapsins are abundant SV (synaptic vesicle)-associated phosphoproteins that regulate synapse formation and function. The highly conserved C-terminal domain E was shown to contribute to several synapsin functions, ranging from formation of the SV reserve pool to regulation of the kinetics of exocytosis and SV cycling, although the molecular mechanisms underlying these effects are unknown. In the present study, we used a synthetic 25-mer peptide encompassing the most conserved region of domain E (Pep-E) to analyse the role of domain E in regulating the interactions between synapsin I and liposomes mimicking the phospholipid composition of SVs (SV–liposomes) and other pre-synaptic protein partners. In affinity-chromatography and cross-linking assays, Pep-E bound to endogenous and purified exogenous synapsin I and strongly inhibited synapsin dimerization, indicating a role in synapsin oligomerization. Consistently, Pep-E (but not its scrambled version) counteracted the ability of holo-synapsin I to bind and coat phospholipid membranes, as analysed by AFM (atomic force microscopy) topographical scanning, and significantly decreased the clustering of SV–liposomes induced by holo-synapsin I in FRET (Förster resonance energy transfer) assays, suggesting a causal relationship between synapsin oligomerization and vesicle clustering. Either Pep-E or a peptide derived from domain C was necessary and sufficient to inhibit both dimerization and vesicle clustering, indicating the participation of both domains in these activities of synapsin I. The results provide a molecular explanation for the effects of domain E in nerve terminal physiology and suggest that its effects on the size and integrity of SV pools are contributed by the regulation of synapsin dimerization and SV clustering.
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Research Article|
January 27 2010
The highly conserved synapsin domain E mediates synapsin dimerization and phospholipid vesicle clustering
Ilaria Monaldi;
Ilaria Monaldi
*Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
†Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, 16163 Genoa, Italy
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Massimo Vassalli;
Massimo Vassalli
‡CNR Institute of Biophysics, 16149 Genoa, Italy
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Angela Bachi;
Angela Bachi
§San Raffaele Scientific Institute, 20132 Milan, Italy
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Silvia Giovedì;
Silvia Giovedì
*Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
‖Istituto Nazionale di Neuroscienze, Italy
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Enrico Millo;
Enrico Millo
*Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
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Flavia Valtorta;
Flavia Valtorta
§San Raffaele Scientific Institute, 20132 Milan, Italy
‖Istituto Nazionale di Neuroscienze, Italy
¶Unit of Molecular Neuroscience, The Italian Institute of Technology, San Raffaele Vita-Salute University, 20132 Milan, Italy
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Roberto Raiteri;
Roberto Raiteri
**Department of Biophysical Engineering and Electronics, University of Genoa, 16145 Genoa, Italy
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Fabio Benfenati;
Fabio Benfenati
1
*Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
†Department of Neuroscience and Brain Technologies, The Italian Institute of Technology, 16163 Genoa, Italy
‖Istituto Nazionale di Neuroscienze, Italy
1To whom correspondence should be addressed (email fabio.benfenati@unige.it).
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Anna Fassio
Anna Fassio
*Department of Experimental Medicine, University of Genoa, 16132 Genoa, Italy
‖Istituto Nazionale di Neuroscienze, Italy
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Publisher: Portland Press Ltd
Received:
May 20 2009
Revision Received:
October 14 2009
Accepted:
November 19 2009
Accepted Manuscript online:
November 19 2009
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2010 Biochemical Society
2010
Biochem J (2010) 426 (1): 55–64.
Article history
Received:
May 20 2009
Revision Received:
October 14 2009
Accepted:
November 19 2009
Accepted Manuscript online:
November 19 2009
Citation
Ilaria Monaldi, Massimo Vassalli, Angela Bachi, Silvia Giovedì, Enrico Millo, Flavia Valtorta, Roberto Raiteri, Fabio Benfenati, Anna Fassio; The highly conserved synapsin domain E mediates synapsin dimerization and phospholipid vesicle clustering. Biochem J 15 February 2010; 426 (1): 55–64. doi: https://doi.org/10.1042/BJ20090762
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