GRAB Neurotransmitter Fluorescent Probe ()

A type of genetically encoded high spatiotemporal resolution neurotransmitter probe

The realization of complex functions of the brain is inseparable from the efficient and specific information exchange and integration between neurons. Neurotransmitters, as important biological small molecules, participate in the information transmission process mediated by chemical synapses between neurons. Most of the known neurotransmitters have corresponding G protein-coupled receptors (GPCRs) as receptors. Therefore, GPCRs, as a type of natural endogenous receptors that can bind to neurotransmitters, are important for constructing genetically encoded neurotransmitters. The preferred backbone for mass probes. The neurotransmitter probe constructed based on the GPCR activation principle is named GRAB probe. Compared with traditional direct measurement methods, GRAB neurotransmitter fluorescent probes have better time resolution, higher molecular specificity, high sensitivity, high signal-to-noise ratio and spatial resolution, making them ideal for studying endogenous neurotransmitters. The release provides powerful tools.

Advantages of the neurotransmitter GRAB probe

1) High specificity;
2) High sensitivity;
3) High temporal and spatial resolution;
4) High signal-to-noise ratio;
5) Non-invasive;
6) No need to build additional detection equipment, it is consistent with the calcium signal detection system.

GRAB probe working principle and application

The conformational changes of the GPCR after binding to the ligand (neurotransmitter) are coupled to the changes in the fluorescence signal of the fluorescent protein, and the release of the neurotransmitter is detected using fluorescence imaging. There is a region in GPCR where the conformation changes most significantly after ligand binding. The cyclically rearranged fluorescent protein is inserted into this region to form a fusion protein. Once the release of a specific neurotransmitter activates the GPCR and causes it to undergo a conformational change, this conformational change will cause the fluorescent protein linked to it to also undergo a conformational change, ultimately changing its fluorescence intensity. Therefore, changes in the fluorescence intensity of fluorescent proteins can be used to indicate dynamic changes in the concentration of neurotransmitters. They named the fluorescent probe GPCR Activation Based Sensor, or GRAB probe for short.

At present, more than 10 new GRAB probes (including dopamine, acetylcholine, norepinephrine, etc.) have been published in relevant literature. Such probes can accurately detect dynamic changes in neurotransmitters in real time. Researchers can express probes in a variety of cultured cells, mouse brain slices, or living Drosophila, zebrafish, mice and other model animals through transfection, virus injection, and construction of transgenic animals. Invisible and intangible chemical signals are transformed into intuitive and easily measurable fluorescent signals, which makes it easier to monitor dynamic changes in neurotransmitters. The emergence of new imaging probes helps to understand changes in neurotransmitters in specific diseases, thus providing new paths for future precision medicine and new drug development.

Schematic diagram illustrating the principle of neurotransmitter GRAB probe

Experimental procedure: A multi-channel optical fiber recording system records the release of endogenous transmitters in freely moving mice

Commonly used GRAB neurotransmitter fluorescent probes

Name	Function
DA	dopamine probe
Ach	Acetylcholine probe
NE	norepinephrine probe
SHT	Serotonin probe
Ado	Adenosine probe
ATP	Adenosine triphosphate probe
CCK	cholecystokinin probe
VIP	Vasoactive intestinal peptide probe
eCB	Endocannabinoid Probes