Abstract
In the nervous system, synapses are cellular junctions at axonal terminal that permit neurotransmitters to pass from a neuron to another. Neurotransmitters from presynaptic neurons are released to the synaptic cleft, and then accepted by receptors embedded on the postsynaptic neuron surface. Through this process, an evoked action potential relays the signal to the next cell. To empty the neurotransmitters in the synaptic vesicles, a group of SNARE proteins are required. Synaptotagmin I is a vesicular SNARE protein, which is mainly located on synaptic vesicles. It contains two independent C2-type Ca2+ sensing domains (called C2A and C2B) in the c-terminal. It has been reported that, in response to Ca2+, Synaptotagmin I utilizes two flexible loops (L1 and L3) of the C2 domain to partially penetrate the hydrophobic core of the lipid bilayer, thus intiate vesicle fusion. According to this finding, we are developing synaptotagmin I-based synaptic probe in conjuction with reconstitutive GFP, and aim to decode the process of neurotransimission in a visible means in living brain. In our pilot study, we expressed pre- and post-synaptic probes seperatly in two types of cells and found that the splitted GFP can be reconstituted in the co-culture system. We are currently testing these probes in the context of neurotransmission and in the Drosophila nervous system. The success of this approach may provide a novel way to detect both transynaptic proximity and function in vivo.