title: Physical and functional interaction of the active zone proteins, CAST, RIM1, and Bassoon, in neurotransmitter release.
abstract: We have recently isolated a novel cytomatrix at the active zone (CAZ)-associated protein, CAST, and found it directly binds another CAZ protein RIM1 and indirectly binds Munc13-1 through RIM1; RIM1 and Munc13-1 directly bind to each other and are implicated in priming of synaptic vesicles. Here, we show that all the CAZ proteins thus far known form a large molecular complex in the brain, including CAST, RIM1, Munc13-1, Bassoon, and Piccolo. RIM1 and Bassoon directly bind to the COOH terminus and central region of CAST, respectively, forming a ternary complex. Piccolo, which is structurally related to Bassoon, also binds to the Bassoon-binding region of CAST. Moreover, the microinjected RIM1- or Bassoon-binding region of CAST impairs synaptic transmission in cultured superior cervical ganglion neurons. Furthermore, the CAST-binding domain of RIM1 or Bassoon also impairs synaptic transmission in the cultured neurons. These results indicate that CAST serves as a key component of the CAZ structure and is involved in neurotransmitter release by binding these CAZ proteins.
authors.affiliation: KAN Research Institute, Kyoto Research Park, Shimogyo-ku, Kyoto 600-8815, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Takao-Rikitsu
authors.forename: Sumiko
authors.initials: S
authors.lastname: Mochida
authors.forename: Eiji
authors.initials: E
authors.lastname: Inoue
authors.forename: Maki
authors.initials: M
authors.lastname: Deguchi-Tawarada
authors.forename: Marie
authors.initials: M
authors.lastname: Inoue
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohtsuka
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Takai
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000502:physiology; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006624:Hippocampus / Q000502:physiology; D007700:Kinetics; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism / Q000502:physiology*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000502:physiology; D013569:Synapses / Q000502:physiology; D014162:Transfection; D016335:Zinc Fingers
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C113688:Bsn protein, rat; D003598:Cytoskeletal Proteins; C406485:ERC2 protein, human; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; C491492:RIMS1 protein, human; D011994:Recombinant Proteins; C107293:Rim protein, mammalian; C491489:Rims1 protein, rat; D019204:GTP-Binding Proteins