Abstract
Gq/11-coupled GPCRs regulate critical physiological processes through calcium mobilization, making intracellular Ca2+ dynamics a key readout for drug discovery and biomarker detection. However, the transient nature of calcium signals necessitates real-time monitoring with specialized equipment, creating barriers for high-throughput screening and limiting accessibility. Here we present CalLuc-2.1, a luminescent calcium biosensor that converts brief Ca2+ spikes into persistent luminescence changes readable tens of minutes after stimulation. By eliminating the need for precisely-timed detection, CalLuc-2.1 enables endpoint measurement of GPCR activation using standard plate readers. We demonstrate robust performance (Z’ > 0.88) across multiple Gq/11-coupled GPCRs in both agonist and antagonist screening formats. Furthermore, CalLuc-2.1 successfully detects endogenous GPCR ligands directly in human serum, offering a simpler alternative to immunoassays and mass spectrometry for biomarker quantification. This approach makes calcium-based GPCR assays accessible to any laboratory with basic luminescence detection capabilities, potentially accelerating both drug discovery and clinical research applications.
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Acknowledgements
We thank the members of Inoue Laboratory for critically reading and editing the manuscript. A.I. was funded by KAKENHI JP21H04791, JP24K21281, and JP25H01016 from the Japan Society for the Promotion of Science (JSPS); JP22ama121038 and JP22zf0127007 from the Japan Agency for Medical Research and Development (AMED); JPMJFR215T and JPMJMS2023 from the Japan Science and Technology Agency (JST); the Uehara Memorial Foundation. M.Y. was funded by KAKENHI JP24K01982, JP24H01266, and JP25H0132 from the JSPS; JPMJPR20EF from the JST; the Lotte Foundation. We would like to thank Editage (www.editage.jp) for English language editing.
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Conceptualization, A.I.; methodology, K.D., R.K., M.Y., and A.I.; investigation, K.D., K.S.; formal analysis, K.D.; validation, K.D., R.K., and M.Y.; visualization, K.D.; writing-original draft, K.D.; writing-review and editing, K.D., R.K., M.Y., and A.I.; funding acquisition, A.I.; supervision, R.K., M.Y., and A.I.
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K.D. is an employee of YAMASA Corporation. A patent application covering the CalLuc sensors described in this manuscript has been filed by YAMASA Corporation and Tohoku University, with K.D., R.K., and A.I. named as inventors (application no. JP2025/178464, pending). K.S., M.Y. declare no potential competing interests.
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Doi, K., Kise, R., Shimizume, K. et al. A luminescent calcium biosensor enabling endpoint measurement of GPCR-mediated calcium signaling. Commun Biol (2026). https://doi.org/10.1038/s42003-026-09920-4
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DOI: https://doi.org/10.1038/s42003-026-09920-4
