Serotonin G Protein-Coupled Receptor-Based Biosensing Modalities in Yeast

Serotonin is a key neurotransmitter involved in numerous physiologicalprocesses and serves as an important precursor for manufacturing bioactive indoleaminesand alkaloids used in the treatment of human pathologies. In humans, serotonin sensingand signaling can occur by 12 G protein-coupled receptors (GPCRs) coupled to G alpha proteins. In yeast, human serotonin GPCRs coupled to G alpha proteins have previously beenshown to function as whole-cell biosensors of serotonin. However, systematiccharacterization of serotonin biosensing modalities between variant serotonin GPCRsand application thereof for high-resolution serotonin quantification is still awaiting. Tosystematically assess GPCR signaling in response to serotonin, we characterized reportergene expression at two different pHs of a 144-sized library encoding all 12 humanserotonin GPCRs in combination with 12 different G alpha proteins engineered in yeast.From this screen, we observed changes in the biosensor sensitivities of >4 orders ofmagnitude. Furthermore, adopting optimal biosensing designs and pH conditionsenabled high-resolution high-performance liquid chromatography-validated sensing of serotonin produced in yeast. Lastly, we usedthe yeast platform to characterize 19 serotonin GPCR polymorphisms found in human populations. While major differences insignaling were observed among the individual polymorphisms when studied in yeast, a cross-comparison of selected variants inmammalian cells showed both similar and disparate results. Taken together, our study highlights serotonin biosensing modalities ofrelevance to both biotechnological and potential human health applications

Automated summary

This study systematically assessed the signaling of various serotonin GPCRs and successfully achieved high-resolution quantification of serotonin using a yeast platform. The study also characterized serotonin GPCR polymorphisms in human populations and observed differences in signaling among these polymorphisms.