Synthetic Membraneless Droplets for Synaptic‐Like Clustering of Lipid Vesicles

Abstract

In eukaryotic cells, the membraneless organelles (MLOs) formed via liquid‐liquid phase separation (LLPS) are found to interact intimately with membranous organelles (MOs). One major mode is the clustering of MOs by MLOs, such as the formation of clusters of synaptic vesicles at nerve terminals mediated by the synapsin‐rich MLOs. Aqueous droplets, including complex coacervates and aqueous two‐phase systems, have been plausible MLO‐mimics to emulate or elucidate biological processes. However, neither of them can cluster lipid vesicles (LVs) like MLOs. In this work, we develop a synthetic droplet assembled from a combination of two different interactions underlying the formation of these two droplets, namely, associative and segregative interactions, which we call segregative‐associative (SA) droplets. The SA droplets cluster and disperse LVs recapitulating the key functional features of synapsin condensates, which can be attributed to the weak electrostatic interaction environment provided by SA droplets. This work suggests LLPS with combined segregative and associative interactions as a possible route for synaptic clustering of lipid vesicles and highlights SA droplets as plausible MLO‐mimics and models for studying and mimicking related cellular dynamics.

Self-assembly of stabilized droplets from liquid–liquid phase separation for higher-order structures and functions

“…The chemical stability of LLPS systems, encompassing both ATPS and coacervate systems, is influenced by factors including pH, ionic strength, and temperature, which impact their intermolecular interactions 10 – 12 . Recently, segregative and associative interactions have been combined to form complex droplets with functions that have not been realized for either ATPS or coacervation 13 , 14 .

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