TY - JOUR T1 - Quantitative Single-Cell Analysis of Signaling Pathways Activated Immediately Downstream of Histamine Receptor Subtypes JF - Molecular Pharmacology JO - Mol Pharmacol SP - 162 LP - 176 DO - 10.1124/mol.116.104505 VL - 90 IS - 3 AU - Jakobus van Unen AU - Ali Rashidfarrokhi AU - Eelco Hoogendoorn AU - Marten Postma AU - Theodorus W. J. Gadella, Jr. AU - Joachim Goedhart Y1 - 2016/09/01 UR - http://molpharm.aspetjournals.org/content/90/3/162.abstract N2 - Genetically encoded biosensors based on Förster resonance energy transfer (FRET) can visualize responses of individual cells in real time. Here, we evaluated whether FRET-based biosensors provide sufficient contrast and specificity to measure activity of G-protein–coupled receptors. The four histamine receptor subtypes (H1R, H2R, H3R, and H4R) respond to the ligand histamine by activating three canonical heterotrimeric G-protein–mediated signaling pathways with a reported high degree of specificity. Using FRET-based biosensors, we demonstrate that H1R activates Gαq. We also observed that H1R activates Gαi, albeit at a 10-fold lower potency. In addition to increasing cAMP levels, most likely via Gαs, we found that the H2R induces Gαq-mediated calcium release. The H3R and H4R activated Gαi with high specificity and a high potency. We demonstrate that a number of FRET sensors provide sufficient contrast to: 1) analyze the specificity of the histamine receptor subtypes for different heterotrimeric G-protein families with single-cell resolution, 2) probe for antagonist specificity, and 3) allow the measurement of single-cell concentration-response curves. ER -