Calcium concentration microdomains

Calcium microdomains are small aggregates, microdomains, of calcium channels located in presynaptic terminals. They are used to create a small area of high calcium concentration to activate various calcium-dependent proteins within the microdomain. This leads to the release of vesicles from the presynaptic terminal, neurotransmission. Transmitter release at chemical synapses, as well as other calcium dependent events triggered by calcium influx via plasmal calcium channels, result from the generation of high calcium concentration microprofiles next to the inner pore of the ionic channel. Such microprofiles have been defined as calcium concentration microdomains (Llinas et al. 1992). These microdomains have been directly visualized at the squid giant synapse using aequorin a photoprotein in conjunction with a high speed single photon video recording system (Llinas et al. 1992) or using total internal reflection fluorescent microscopy in conjunction with calcium indicator dyes (Serulle et al 2006), This visualization demonstrate the apposition of calcium concentration microdomains and synaptic release sites at single synaptic terminals. These findings demonstrate the close apposition of calcium entry and release sites and the dynamics of such site locations over time.

References

* Llinas, R., Sugimori, M. and Silver, R.B. Microdomains of high calcium concentration in a presynaptic terminal. Science. 256, 677-679, 1992.

* Serulle, Y.,Sugimori, M., Llinas, R. Imaging synaptosomal calcium concentration microdomains and vesicle fusion by using total internal reflection fluorescent microscopy Proc. Natl. Acad. Sci. USA 104: 1697-1702, 2007