Quantitative super-resolution imaging of Bruchpilot distinguishes active zone states

Ehmann, Nadine and van de Linde, Sebastian and Alon, Amit and Ljaschenko, Dmitrij and Keung, Xi Zhen and Holm, Thorge and Rings, Annika and DiAntonio, Aaron and Hallermann, Stefan and Ashery, Uri and Heckmann, Manfred and Sauer, Markus and Kittel, Robert J. (2014) Quantitative super-resolution imaging of Bruchpilot distinguishes active zone states. Nature Communications, 5. ISSN 2041-1723

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    Abstract

    The precise molecular architecture of synaptic active zones (AZs) gives rise to different structural and functional AZ states that fundamentally shape chemical neurotransmission. However, elucidating the nanoscopic protein arrangement at AZs is impeded by the diffraction-limited resolution of conventional light microscopy. Here we introduce new approaches to quantify endogenous protein organization at single-molecule resolution in situ with super-resolution imaging by direct stochastic optical reconstruction microscopy (dSTORM). Focusing on the Drosophila neuromuscular junction (NMJ), we find that the AZ cytomatrix (CAZ) is composed of units containing ~137 Bruchpilot (Brp) proteins, three quarters of which are organized into about 15 heptameric clusters. We test for a quantitative relationship between CAZ ultrastructure and neurotransmitter release properties by engaging Drosophila mutants and electrophysiology. Our results indicate that the precise nanoscopic organization of Brp distinguishes different physiological AZ states and link functional diversification to a heretofore unrecognized neuronal gradient of the CAZ ultrastructure.