抄録
A novel protein for cytomatrix at the active zone (CAZ), named CAST, directly binds RIM1 and indirectly binds to Munc13 through RIM1. The interaction of Munc13-1 with RIM1 is implicated in priming of synaptic vesicles. All the CAZ proteins, thus far known, including CAST, RIM1, Munc13-1, Bassoon and Piccolo, from a large molecular complex in the brain. RIM1 and Bassoon bind directly to the C-terminus and central region of CAST, forming a ternary complex. To examine the functional role for CAST in neurotransmitter release, we monitored changes in synaptic transmission produced by perturbing the interaction of CAST with the other CAZ proteins in rat superior cervical ganglion neurons in culture. These neurons express CAST, RIM1 and Bassoon at presynaptic terminals, as shown by co-localization of these proteins with synaptiphysin, a synaptic vesicle associated protein. The synaptic transmission is reduced by microinjection of RIM1- or Bassoon-binding region of CAST. Furthermore, the CAST-binding domain of RIM1 or Bassoon also impairs synaptic transmission. These results indicate that CAST serves as a key component for the CAZ structure and is involved in neurotransmitter release by directly binding these CAZ proteins. [Jpn J Physiol 54 Suppl:S147 (2004)]
