GPCR-Based Dopamine Sensors—A Detailed Guide to Inform Sensor Choice for In Vivo Imaging

Abstract

Understanding how dopamine (DA) encodes behavior depends on technologies that can reliably monitor DA release in freely-behaving animals. Recently, red and green genetically encoded sensors for DA (dLight, GRAB-DA) were developed and now provide the ability to track release dynamics at a subsecond resolution, with submicromolar affinity and high molecular specificity. Combined with rapid developments in in vivo imaging, these sensors have the potential to transform the field of DA sensing and DA-based drug discovery. When implementing these tools in the laboratory, it is important to consider there is not a ‘one-size-fits-all’ sensor. Sensor properties, most importantly their affinity and dynamic range, must be carefully chosen to match local DA levels. Molecular specificity, sensor kinetics, spectral properties, brightness, sensor scaffold and pharmacology can further influence sensor choice depending on the experimental question. In this review, we use DA as an example; we briefly summarize old and new techniques to monitor DA release, including DA biosensors. We then outline a map of DA heterogeneity across the brain and provide a guide for optimal sensor choice and implementation based on local DA levels and other experimental parameters. Altogether this review should act as a tool to guide DA sensor choice for end-users.

Dopaminergic Dysregulation in Syndromic Autism Spectrum Disorders: Insights From Genetic Mouse Models

“…Many of the findings discussed in this review come from in vitro and ex vivo assays that have provided fundamental insights into the state of the DA system in syndromic ASD mouse models. Recent developments in DA monitoring, including GRAB DA and D-Light GPCR-based DA sensors (Labouesse et al, 2020;Patriarchi et al, 2020;Sun et al, 2020), coupled to spectral-and depth-resolved fiber photometry (Meng et al, 2018;Pisano et al, 2019), now grant unprecedented access to monitoring DA neurotransmission in vivo. The use of these newly developed tools to monitor DA dynamics in awake behaving animals, potentially across multiple brain regions simultaneously, will allow for comprehensive mapping of brain-wide DA neurotransmission dynamics and changes associated ASD.…”

The critical balance between dopamine D2 receptor and RGS for the sensitive detection of a transient decay in dopamine signal

“…However, the penetration of an observation probe (5~8 μm diameter) might interfere with the DA dynamics, because the cycle of DA release, diffusion, and uptake is known to occur only in a span of ~10 μm [ 42 ]. Recent DA observation using an ultrafast fluorescent probe shows the faster dynamics of DA ( t 1/2 ~ 0.1 s) [ 43 , 44 ]. Thus, based on a preceding model [ 45 ], we first simulated the rapid concentration dynamics of DA, [ DA ], as follows ( Figs 1C and 2A ): where T dip is the duration of a DA pause, t DA,delay is the onset time of the DA pause, [ DA ] dip is the bottom concentration of produced DA dip, and [ DA ] opto is the amplitude of DA signal by a single light pulse.…”

“…Thus, based on a preceding model [ 45 ], we first simulated the rapid concentration dynamics of DA, [ DA ], as follows ( Figs 1C and 2A ): where T dip is the duration of a DA pause, t DA,delay is the onset time of the DA pause, [ DA ] dip is the bottom concentration of produced DA dip, and [ DA ] opto is the amplitude of DA signal by a single light pulse. k cat,DAT [ DAT ] and [ DA ] opto were determined so as to give an average concentration of 0.5 μM and a half-valued period of 0.1 s [ 1 , 44 ].…”

HIV-Associated Apathy/Depression and Neurocognitive Impairments Reflect Persistent Dopamine Deficits

“…DA biosensors were developed by inserting a genetically encoded, circularly permuted fluorescent protein (e.g., Green: cpGFP, Red: cpmApple) into the third intracellular loop of the naturally occurring human DA receptor. When DA is released, it binds to the endogenous ligand, causing a rapid conformational change in the GPCR, a conformational change that induces a profound increase in fluorescence intensity (i.e., 90-900%, for a review, see [164]; Figure 2C). DA biosensors exhibit high selectivity, molecular specificity, affinity (sub-micromolar) and resolution (sub-second [160][161][162][163]165]), making them ideally suited for tracking DA release.…”

“…However, DA biosensors may be limited by low basal fluorescence levels, which precludes the detection of basal DA levels. A more comprehensive discussion of GPCR biosensors for DA is provided by Labouesse et al [164].…”