TY  - JOUR
AU  - Neuhaus, Charlotte
AU  - Alfken, Jette
AU  - Frost, Jakob
AU  - Matthews, Lauren
AU  - Hoffmann, Christian
AU  - Ganzella, Marcelo
AU  - Milovanovic, Dragomir
AU  - Salditt, Tim
TI  - Morphology and intervesicle distances in condensates of synaptic vesicles and synapsin.
JO  - Biophysical journal
VL  - 123
IS  - 23
SN  - 0006-3495
CY  - Bethesda, Md.
PB  - Soc.
M1  - DZNE-2024-01394
SP  - 4123 - 4134
PY  - 2024
AB  - Synaptic vesicle clusters or pools are functionally important constituents of chemical synapses. In the so-called reserve and the active pools, neurotransmitter-loaded synaptic vesicles (SVs) are stored and conditioned for fusion with the synaptic membrane and subsequent neurotransmitter release during synaptic activity. Vesicle clusters can be considered as so-called membraneless compartments, which form by liquid-liquid phase separation. Synapsin as one of the most abundant synaptic proteins has been identified as a major driver of pool formation. It has been shown to induce liquid-liquid phase separation and form condensates on its own in solution, but also has been shown to integrate vesicles into condensates in vitro. In this process, the intrinsically disordered region of synapsin is believed to play a critical role. Here, we first investigate the solution structure of synapsin and SVs separately by small-angle x-ray scattering. In the limit of low momentum transfer q, the scattering curve for synapsin gives clear indication for supramolecular aggregation (condensation). We then study mixtures of SVs and synapsin-forming condensates, aiming at the morphology and intervesicle distances, i.e., the structure of the condensates in solution. To obtain the structure factor S(q) quantifying intervesicle correlation, we divide the scattering curve of condensates by that of pure SV suspensions. Analysis of S(q) in combination with numerical simulations of cluster aggregation indicates a noncompact fractal-like vesicular fluid with rather short intervesicle distances at the contact sites.
KW  - Synapsins: metabolism
KW  - Synapsins: chemistry
KW  - Synaptic Vesicles: metabolism
KW  - Synaptic Vesicles: chemistry
KW  - Animals
KW  - Scattering, Small Angle
KW  - X-Ray Diffraction
KW  - Rats
KW  - Biomolecular Condensates: chemistry
KW  - Biomolecular Condensates: metabolism
KW  - Synapsins (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C2  - pmc:PMC11628805
C6  - pmid:39520054
DO  - DOI:10.1016/j.bpj.2024.11.004
UR  - https://pub.dzne.de/record/273920
ER  -