DRACC1, a major postsynaptic protein, regulates the condensation of postsynaptic proteins via liquid-liquid phase separation

Abstract

Numerous proteome analyses have been conducted on the postsynaptic density (PSD), a protein condensate beneath the postsynaptic membrane of excitatory synapses. Each has identified several hundred to thousands of proteins. While proteins with predictable functions have been well studied, functionally uncharacterized proteins are mostly overlooked. In this study, we perform a meta-analysis of the 35 PSD proteome datasets, including 5,869 proteins, identifying 97 uncharacterized proteins that appeared in multiple datasets. We focus on the top-ranked protein, FAM81A, renamed DRACC1. DRACC1 is expressed in forebrain neurons and enriched at the synapse. DRACC1 interacts with PSD proteins, including PSD-95, SynGAP, and NMDA receptors, and promotes liquid-liquid phase separation of those proteins. Consistently, the downregulation of DRACC1 in neurons causes a decrease in the size of PSD-95 puncta and the frequency of neuronal firing. Our results characterize DRACC1 as a novel synaptic protein facilitating the assembly of proteins within PSD. It also indicates the effectiveness of a meta-analytic approach of existing proteome datasets in identifying uncharacterized proteins.