Binding to Rab3A-interacting molecule RIM regulates the presynaptic recruitment of Munc13-1 and ubMunc13-2.
Transmitter release at synapses between nerve cells is spatially restricted to active zones, where synaptic vesicle docking, priming, and Ca2+-dependent fusion take place in a temporally highly coordinated manner. Munc13s are essential for priming synaptic vesicles to a fusion competent state, and their specific active zone localization contributes to the active zone restriction of transmitter release and the speed of excitation-secretion coupling. However, the molecular mechanism of the active zone recruitment of Munc13s is not known. We show here that the active zone recruitment of Munc13 isoforms Munc13-1 and ubMunc13-2 is regulated by their binding to the Rab3A-interacting molecule RIM1alpha, a key determinant of long term potentiation of synaptic transmission at mossy fiber synapses in the hippocampus. We identify a single point mutation in Munc13-1 and ubMunc13-2 (I121N) that, depending on the type of assay used, strongly perturbs or abolishes RIM1alpha binding in vitro and in cultured fibroblasts, and we demonstrate that RIM1alpha binding-deficient ubMunc13-2(I121) is not efficiently recruited to synapses. Moreover, the levels of Munc13-1 and ubMunc13-2 levels are decreased in RIM1alpha-deficient brain, and Munc13-1 is not properly enriched at active zones of mossy fiber terminals of the mouse hippocampus if RIM1alpha is absent. We conclude that one function of the Munc13/RIM1alpha interaction is the active zone recruitment of Munc13-1 and ubMunc13-2.
Andrews-Zwilling
Yaisa S
YS
Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, D-37075 Göttingen, Germany.
Kawabe
Hiroshi
H
Reim
Kerstin
K
Varoqueaux
Frederique
F
Brose
Nils
N
D000595:Amino Acid Sequence; D000818:Animals; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013569:Synapses / Q000378:metabolism; D020826:rab3A GTP-Binding Protein / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; C491490:Rims1 protein, mouse; C491489:Rims1 protein, rat; C503321:Unc13a protein, mouse; C103912:Unc13a protein, rat; C485549:Unc13b protein, mouse; C117991:Unc13b protein, rat; D019204:GTP-Binding Proteins; D020826:rab3A GTP-Binding Protein