Ryuichi Shigemoto, Institute of Science and Technology Austria (IST Austria)
High resolution localization of voltage-dependent calcium channels and related proteins in CNS synapses
Activation of the presynaptic voltage-dependent calcium channels (VDCCs) triggers vesicular release of neurotransmitters. The coupling distance between VDCCs and the vesicular Ca2+ sensor for release varies depending on types of VDCCs and synapses from loose to tight coupling. However, the precise localization of different types of VDCCs, as well as their related proteins involved in regulation of VDCC localization and function, has not been well known within the presynaptic zone (AZ) in axon terminals because of technical difficulties including lack of suitable antibodies for immunolabeling. Here, we used new VDCC antibodies coupled with preembedding and freeze-fracture replica immunogold labeling for VGCCs at the AZs of central mammalian synapses. Immunogold particles for P/Q- and N-type VDCCs showed small clusters within the AZ, whereas R-type VDCC was mainly distributed outside of AZ. Particles for RIM and Munc13-1 were concentrated at the AZ making small clusters and colocalized with Cav2.1, whereas CASK and Neurexin were distributed more diffusely in the AZ. SNARE proteins were distributed all over the presynaptic elements and not particularly concentrated in the AZ. To analyze potential modification of these distribution patterns accompanied with neuronal activity, we examined transgenic rats expressing channelrhodopsin-2 in cerebellar granule cells with 2-minute continuous light stimulation in vivo. We found that the number of Cav2.1 was reduced shortly after the stimulation in the AZ, increased at 30min and recovered to the control level within 4 hours. These changes in VDCC localization may contribute to the presynaptic plasticity by regulating the release probability and coupling distance.
Neuroscience Seminar Series, MONDAY, October 6, 2014 at 11:30 am (note exceptional day)
Salle des Conférences (R229)