A Munc13/RIM/Rab3 tripartite complex: from priming to plasticity?
alpha-RIMs and Munc13s are active zone proteins that control priming of synaptic vesicles to a readily releasable state, and interact with each other via their N-terminal sequences. The alpha-RIM N-terminal sequence also binds to Rab3s (small synaptic vesicle GTPases), an interaction that regulates presynaptic plasticity. We now demonstrate that alpha-RIMs contain adjacent but separate Munc13- and Rab3-binding sites, allowing formation of a tripartite Rab3/RIM/Munc13 complex. Munc13 binding is mediated by the alpha-RIM zinc-finger domain. Elucidation of the three-dimensional structure of this domain by NMR spectroscopy facilitated the design of a mutation that abolishes alpha-RIM/Munc13 binding. Selective disruption of this interaction in the calyx of Held synapse decreased the size of the readily releasable vesicle pool. Our data suggest that the ternary Rab3/RIM/Munc13 interaction approximates synaptic vesicles to the priming machinery, providing a substrate for presynaptic plasticity. The modular architecture of alpha-RIMs, with nested binding sites for Rab3 and other targets, may be a general feature of Rab effectors that share homology with the alpha-RIM N-terminal sequence.
Dulubova
Irina
I
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-8816, USA.
Lou
Xuelin
X
Lu
Jun
J
Huryeva
Iryna
I
Alam
Amer
A
Schneggenburger
Ralf
R
Südhof
Thomas C
TC
Rizo
Josep
J
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002151:Calorimetry; D004594:Electrophysiology; D004926:Escherichia coli; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D016415:Sequence Alignment; D013572:Synaptic Vesicles / Q000378:metabolism*; D020692:rab3 GTP-Binding Proteins / Q000378:metabolism*
D046912:Multiprotein Complexes; D009419:Nerve Tissue Proteins; C107293:Rim protein, mammalian; C485548:UNC13B protein, human; D005982:Glutathione Transferase; D019204:GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins