Mapping the proteome of the synaptic cleft through proximity labeling reveals new cleft proteins
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AbstractSynapses are specialized neuronal cell-cell contacts that underlie network communication in the mammalian brain. Across neuronal populations and circuits, a diverse set of synapses is utilized, and they differ in their molecular composition to enable heterogenous connectivity patterns and functions. In addition to pre- and post-synaptic specializations, the synaptic cleft is now understood to be an integral compartment of synapses that contributes to their structural and functional organization. Aiming to map the cleft proteome, this study applied a peroxidase-mediated proximity labeling approach and used the excitatory synaptic cell adhesion protein SynCAM 1 fused to horseradish peroxidase (HRP) as a reporter in cultured cortical neurons. This reporter marked excitatory synapses as measured by confocal microcopy and was targeted to the edge zone of the synaptic cleft as determined using 3D dSTORM super-resolution imaging. Proximity labeling with a membrane-impermeant biotin-phenol compound restricted labeling to the cell surface, and Label-Free Quantitation (LFQ) mass spectrometry combined with ratiometric HRP tagging of membrane vs. synaptic surface proteins was used to identify the proteomic content of excitatory clefts. Novel cleft candidates were identified, and Receptor-type tyrosine-protein phosphatase zeta was selected and successfully validated. This study supports the robust applicability of peroxidase-mediated proximity labeling for synaptic cleft proteomics and its potential for understanding synapse heterogeneity in health and changes in diseases such as psychiatric disorders and addiction. Copyright 2018 by the authors.
SponsorsFunding: This research was funded by NIH R01 DA018928 (to T.B.), MH080046 (to T.A.B.), MH116583 (to A.M.R.) and NIH P30 DA018343 (to T.T.L, and to T.C. for a pilot award). The Orbitrap Fusion used for mass spectral data collection was funded by NIH SIG from the Office of The Director, National Institutes of Health of the National Institutes of Health under Award Number S10OD018034.
Receptor-type tyrosine-protein phosphatase zeta
Identifier to cite or link to this itemhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85059418287&doi=10.3390%2fproteomes6040048&partnerID=40&md5=5f19f7c2d9efeccc19fd1e50723f8fb9; http://hdl.handle.net/10713/9129