title: Munc18-1 redistributes in nerve terminals in an activity- and PKC-dependent manner.
abstract: Munc18-1 is a soluble protein essential for synaptic transmission. To investigate the dynamics of endogenous Munc18-1 in neurons, we created a mouse model expressing fluorescently tagged Munc18-1 from the endogenous munc18-1 locus. We show using fluorescence recovery after photobleaching in hippocampal neurons that the majority of Munc18-1 trafficked through axons and targeted to synapses via lateral diffusion together with syntaxin-1. Munc18-1 was strongly expressed at presynaptic terminals, with individual synapses showing a large variation in expression. Axon-synapse exchange rates of Munc18-1 were high: during stimulation, Munc18-1 rapidly dispersed from synapses and reclustered within minutes. Munc18-1 reclustering was independent of syntaxin-1, but required calcium influx and protein kinase C (PKC) activity. Importantly, a PKC-insensitive Munc18-1 mutant did not recluster. We show that synaptic Munc18-1 levels correlate with synaptic strength, and that synapses that recruit more Munc18-1 after stimulation have a larger releasable vesicle pool. Hence, PKC-dependent dynamic control of Munc18-1 levels enables individual synapses to tune their output during periods of activity.
authors.affiliation: Department of Functional Genomics and Clinical Genetics, Center for Neurogenomics and Cognitive Research, Neuroscience Campus Amsterdam, VU University Amsterdam and VU Medical Center, 1081 HV Amsterdam, Netherlands.
authors.forename: Tony
authors.initials: T
authors.lastname: Cijsouw
authors.forename: Jens P
authors.initials: JP
authors.lastname: Weber
authors.forename: Jurjen H
authors.initials: JH
authors.lastname: Broeke
authors.forename: Jantine A C
authors.initials: JA
authors.lastname: Broek
authors.forename: Desiree
authors.initials: D
authors.lastname: Schut
authors.forename: Tim
authors.initials: T
authors.lastname: Kroon
authors.forename: Ingrid
authors.initials: I
authors.lastname: Saarloos
authors.forename: Matthijs
authors.initials: M
authors.lastname: Verhage
authors.forename: Ruud F
authors.initials: RF
authors.lastname: Toonen
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D004594:Electrophysiology; D055879:Gene Knock-In Techniques; D051379:Mice; D051938:Munc18 Proteins / Q000032:analysis* / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport; D013569:Synapses / Q000378:metabolism; D050827:Syntaxin 1 / Q000378:metabolism
chemical_list: D051938:Munc18 Proteins; C497938:Stxbp1 protein, mouse; D050827:Syntaxin 1; D011493:Protein Kinase C