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Shigeki Kiyonaka, Hiroshi Nakajima, Yoshinori Takada, Yamato Hida, Toshinori Yoshioka, Akari Hagiwara, Isao Kitajima, Yasuo Mori, Toshihisa Ohtsuka, Physical and functional interaction of the active zone protein CAST/ERC2 and the β-subunit of the voltage-dependent Ca2+ channel, The Journal of Biochemistry, Volume 152, Issue 2, August 2012, Pages 149–159, https://doi.org/10.1093/jb/mvs054
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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 Ca2+-dependent release of neurotransmitters. Here, we show an interaction of CAST with voltage-dependent Ca2+ channels (VDCCs), which are essential for regulating neurotransmitter release triggered by depolarization-induced Ca2+ influx at the active zone. Using a biochemical assay, we showed that CAST was coimmunoprecipitated with the VDCC β4-subunit from the mouse brain. A pull-down assay revealed that the VDCC β4-subunit interacted directly with at least the N- and C-terminal regions of CAST. The II–III linker of VDCC α1-subunit also interacted with C-terminal regions of CAST; however, the interaction was much weaker than that of β4-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.
