A family of RIM-binding proteins regulated by alternative splicing: Implications for the genesis of synaptic active zones.
RIMs are presynaptic active zone proteins that regulate neurotransmitter release. We describe two related genes that encode proteins with identical C-terminal sequences that bind to the conserved PDZ domain of RIMs via an unusual PDZ-binding motif. These proteins were previously reported separately as ELKS, Rab6-interacting protein 2, and CAST, leading us to refer to them by the acronym ERC. Alternative splicing of the C terminus of ERC1 generates a longer ERC1a variant that does not bind to RIMs and a shorter ERC1b variant that binds to RIMs, whereas the C terminus of ERC2 is synthesized only in a single RIM-binding variant. ERC1a is expressed ubiquitously as a cytosolic protein outside of brain; ERC1b is detectable only in brain, where it is both a cytosolic protein and an insoluble active zone component; and ERC2 is brain-specific but exclusively localized to active zones. Only brain-specific ERCs bind to RIMs, but both ubiquitous and brain-specific ERCs bind to Rab6, a GTP-binding protein involved in membrane traffic at the Golgi complex. ERC1a and ERC1b/2 likely perform similar functions at distinct localizations, indicating unexpected connections between nonneuronal membrane traffic at the Golgi complex executed via Rab6 and neuronal membrane traffic at the active zone executed via RIMs.
Wang
Yun
Y
The Center for Basic Neuroscience and Department of Molecular Genetics, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390-9111, USA.
Liu
Xinran
X
Biederer
Thomas
T
Südhof
Thomas C
TC
D048868:Adaptor Proteins, Signal Transducing; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D019204:GTP-Binding Proteins; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D000090204:Mesothelin; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism*; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D016704:Synapsins / Q000378:metabolism; D013570:Synaptic Membranes / Q000378:metabolism*; D009435:Synaptic Transmission; D014018:Tissue Distribution; D020691:rab GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; C468925:ERC1 protein, human; C406485:ERC2 protein, human; C486769:Erc1 protein, mouse; D008565:Membrane Proteins; C000715529:Msln protein, rat; D009419:Nerve Tissue Proteins; D011518:Proto-Oncogene Proteins; C491492:RIMS1 protein, human; C107293:Rim protein, mammalian; C491490:Rims1 protein, mouse; C491489:Rims1 protein, rat; D016704:Synapsins; D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D000090204:Mesothelin