title: Physical and functional interaction of the active zone protein CAST/ERC2 and the β-subunit of the voltage-dependent Ca(2+) channel.
abstract: In the nerve terminals, the active zone protein CAST/ERC2 forms a protein complex with the other active zone proteins ELKS, Bassoon, Piccolo, RIM1 and Munc13-1, and is thought to play an organizational and functional role in neurotransmitter release. However, it remains obscure how CAST/ERC2 regulates the Ca(2+)-dependent release of neurotransmitters. Here, we show an interaction of CAST with voltage-dependent Ca(2+) channels (VDCCs), which are essential for regulating neurotransmitter release triggered by depolarization-induced Ca(2+) influx at the active zone. Using a biochemical assay, we showed that CAST was coimmunoprecipitated with the VDCC β(4)-subunit from the mouse brain. A pull-down assay revealed that the VDCC β(4)-subunit interacted directly with at least the N- and C-terminal regions of CAST. The II-III linker of VDCC α(1)-subunit also interacted with C-terminal regions of CAST; however, the interaction was much weaker than that of β(4)-subunit. Furthermore, coexpression of CAST and VDCCs in baby hamster kidney cells caused a shift in the voltage dependence of activation towards the hyperpolarizing direction. Taken together, these results suggest that CAST forms a protein complex with VDCCs, which may regulate neurotransmitter release partly through modifying the opening of VDCCs at the presynaptic active zones.
authors.affiliation: Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kiyonaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakajima
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Takada
authors.forename: Yamato
authors.initials: Y
authors.lastname: Hida
authors.forename: Toshinori
authors.initials: T
authors.lastname: Yoshioka
authors.forename: Akari
authors.initials: A
authors.lastname: Hagiwara
authors.forename: Isao
authors.initials: I
authors.lastname: Kitajima
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Ohtsuka
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018377:Neurotransmitter Agents / Q000378:metabolism; D021122:Protein Subunits; D013569:Synapses / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D003598:Cytoskeletal Proteins; C505599:Erc2 protein, mouse; D018377:Neurotransmitter Agents; D021122:Protein Subunits