Modulating the Properties of GPCR-Based Sensors Via C-Terminus Isoforms

G-protein coupled receptors (GPCRs) play a key role in chemical biosensing, detecting chemicals from odorants and hormones to neurotransmitters and peptides. GPCR-based sensors in yeast can be rapidly engineered by coupling human GPCRs to the yeast mating pathway, resulting in cell fluorescence or luminescence upon chemical detection. Modulating the properties of GPCR-based sensors including their dynamic and linear ranges is nontrivial, often requiring the engineering of the yeast cell machinery. Here, we explore the use of GPCR C-terminal isoforms to modulate the properties of chemical biosensors. As a proof-of-concept, we leverage nine naturally occurring serotonin receptor 4 (5-HTR₄) C-terminus isoforms to construct serotonin sensors with dynamic ranges spanning from 2- to 8.5-fold increases in signal after activation for a single integrated version, and from 3.4- to 62.7-fold for a double integrated version, and linear ranges reaching 5 orders of magnitude, from 10^-8 to 10^-3 M serotonin. Interestingly, the 5-HTR₄ isoform-based sensors had different properties based on the chemical used to activate them, hinting at the potential differential activation of 5-HTR₄ C-terminal isoforms in the body. Taken together, this work debuts the use of GPCR isoforms as a new strategy to rapidly modulate the dynamic and linear ranges of GPCR-based sensors in yeast.