Fig. 1. Arc selectively disperses Stargazin in reconstituted PSD condensates.

a Schematic diagram illustrating the imaging-based assay to screen specific synaptic targets of Arc by using reconstituted PSD condensates. In each imaging experiment, only one protein was sparsely labeled (at 2%) with iFluor-488. Unless otherwise specified, fluorescence labeling of proteins was at the 2% level throughout the study. b Confocal microscope images showing the enrichments of iFluor-488 proteins in 7× PSD droplets during Arc titration. c Quantitative analysis showing the enrichment changes of each PSD component during Arc titration. The fluorescent intensities of the protein in each titration were normalized to that obtained in the absence of Arc. Results were from three independent batches of imaging assays and presented as means ± SD. d DIC and fluorescence images showing the dispersion of the Stg/PSD-95 (15:5 µM) condensates by Arc. e DIC and fluorescence images showing that Arc cannot disperse the GluN2B/PSD-95 (15:5 µM) condensates. f Quantification data showing the droplet numbers formed by Stg and PSD-95 in d and by GluN2B/PSD-95 in e during the Arc titrations. At each titration point, the droplet number was normalized to that obtained in the absence of Arc. Results were from three independent batches of imaging assays and presented as means ± SD. g ITC-based measurements comparing Arc’s binding to Stg, GluN2B and PSD-95. 200 µM Arc GAG domain in syringe was titrated to 20 µM Stg, GluN2B and PSD-95, respectively, in reaction cell.