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[Preprint]. 2023 Dec 23:2023.12.22.573055. [Version 1] doi: 10.1101/2023.12.22.573055

Figure 3.

Figure 3.

Only a subpopulation of release sites is enriched with GluN2 subunits. a) Example synapse of DNA-PAINT localizations of PSD-95, GluN2A, GluN2B, and Munc13–1 showing arrangement of receptor subunits relative to release sites. Markers as described in Fig 2a. b-c) Characterization of Munc13–1 NCs. Munc13–1 autocorrelation decayed rapidly and plateaued below one (b), consistent with its many small NCs (c). d) Munc13–1 NCs were, on average, de-enriched with GluN2A (left), and GluN2B (right) at distances <55 nm (shading). e-j) A subset of Munc13–1 NCs were enriched with GluN2 subunits. Schematic indicates possible configurations of GluN2 and Munc13–1 NCs (e). Schematic of NC pairing to reveal stereotyped distances of closely-associated NCs (f). Paired Munc13–1 NCs were enriched with GluN2A and GluN2B within 55 nm of their center (g). 21.8% and 24.0% of Munc13–1 NCs were statistically enriched with GluN2A or GluN2B (h), 26.0% and 32.7% of Munc13–1 NCs had a GluN2A or GluN2B NC peak within 60 nm (i), and 10.6% and 11.3% of Munc13–1 NCs spatially overlapped with GluN2A or GluN2B NCs (j), respectively. Data in b, d and g are means ± SEM shading. Points in c (left) are synapses and (right) NCs, with lines at mean ± SEM. Data in i are shown as frequency histograms (20 nm bins), with dashed line indicating the division summarized in inset pie charts.