Synaptic vesicle pool condensates are clusters of synaptic vesicles at presynaptic sites. Synapsin is the abundant protein associated with synaptic vesicles condensates. CaMKII phosphorylation was found to affect synapsin's ability to phase separate in vitro. CaMKII phosphorylation resulted in the dissolution of synapsin/vesicle condensates, implying negative regulation. In vivo, a triple deletion of all three mammalian synapsins resulted in more distributed vesicle pools; however, whether phase separation activity is directly responsible for this phenotype has to be determined. CaMKII phosphorylation of synapsin may modify these condensates for this purpose, as presynaptic CaMKII is critical for plasticity ( reviewed in 33979706).
McDonald NA, Shen K. Finding functions of phase separation in the presynapse. Curr Opin Neurobiol. 2021 Aug;69:178-184. doi: 10.1016/j.conb.2021.04.001. Epub 2021 May 9. PMID: 33979706.