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. Author manuscript; available in PMC: 2018 Nov 28.
Published in final edited form as: Chemosensors (Basel). 2017 Nov 28;5(4):32. doi: 10.3390/chemosensors5040032

Figure 4. Schematic representation of genetically encoded indicators for synaptic activity.

Figure 4

(A) iGluSnFR is a genetically encoded single-FP-based glutamate indicator which contains a cpGFP inserted into the bacterial periplasmic glutamate binding domain (GlutI). Glutamate binding induced conformation change of Gltl results in deprotonation and fluorescence enhancement of cpGFP; (B) sypHTomato is a genetically encoded fluorescent reporter for synaptic vesicle recycling. It consists of a pH-sensitive red fluorescent protein (pHTomato) fused to the C-terminus of the vesicular protein domain Synaptophysin that localizes the probe to vesicle membrane. During membrane fusion, FP is switched from the low pH environment of vesicle to the neutral extracellular space, which leads to pH-dependent fluorescence changes. Subsequent vesicle recycling events reset the pH cycle.