G protein-coupled receptors (GPCRs) are integral membrane proteins crucial for sensing extracellular signals, including hormones, neurotransmitters, and environmental cues. These receptors initiate intracellular signaling cascades upon activation, ultimately regulating a myriad of physiological processes. Central to GPCR function are G proteins, comprising subfamilies such as Gs, Gi/o, Gq/11, and G12/13, which orchestrate downstream signaling events, including the modulation of cyclic adenosine monophosphate (cAMP), calcium mobilization, and extracellular signal-regulated kinase (ERK) activation [1]. Traditionally, second messenger assays measuring cAMP accumulation, calcium mobilization, and ERK phosphorylation have been pivotal in deciphering GPCR activity, particularly in drug discovery endeavors [2]. However, these conventional assays often provide limited information on intermediate signaling events due to pathway crosstalk and signal amplification [3]. Also, most second messenger assays are primarily endpoint measurements and do not allow practical measurement of the kinetics of signaling. The emergence of resonance energy transfer (RET) techniques, notably Fluorescence Resonance Energy Transfer (FRET) and Bioluminescence Resonance Energy Transfer (BRET), has revolutionized the study of GPCRs by enabling real-time monitoring of protein-protein interactions and intracellular signaling dynamics[4]. FRET and BRET sensors operate on the principle of energy transfer between a fluorescent or luminescent donor and acceptor molecules within close proximity, typically within 100Å. These biosensors have facilitated the investigation of various aspects of GPCR signaling, including ligand binding (e.g NanoBRET ligand binding [5]), effector protein recruitment assays (e.g G protein recruitment assay [6], mini-G recruitment assay [7], GRK and β-arrestin recruitment assays [8]), G protein activation (e.g TRUPATH assay [9]), receptor trafficking ( e.g FYVE assay [10]),  β-arrestin dynamics ( e.g FLAsH biosensor [11]), cAMP production (e.g CAMYEL assay [12]) , and ERK activity (e.g YEN assay [13]), among others. One of the significant advantages of FRET and BRET-based sensors is their ability to provide real-time readouts of pharmacological activity, allowing for the determination of drug kinetics—a critical aspect in drug development [14]. Moreover, these experiments can be conducted in live cells, preserving the physiological context and minimizing artifacts associated with sample preparation for endpoint measurements. Despite their immense potential, utilizing FRET and BRET sensors in GPCR research comes with challenges, including expensive cost of reagents, optimizing sensor expression levels and adapting these systems to disease-relevant models. Addressing these hurdles is essential for translating findings from cellular models to clinically relevant scenarios. Some innovative solutions have been the development of the BERKY and the ONE-GO biosensors, designed to facilitate their application in disease models[3, 15]. BERKY consists of a membrane linker, a BRET donor, an ER/K α-helix linker, a BRET acceptor, and an active G protein detector. The ONE-GO biosensors, designed in a single vector, incorporate a G protein tagged with a YFP acceptor and a G protein detector tagged with an Nluc donor. Both BERKY and ONE-GO biosensors are engineered to detect the GTP-bound Gα subunit, serving as a proxy for G protein activation and have been optimized for use in detecting GPCR activity in primary cells. In conclusion, FRET and BRET-based sensors have transformed the landscape of GPCR research, offering unprecedented insights into the intricacies of GPCR signaling. These techniques not only enhance our understanding of fundamental cellular processes, but also hold immense promise in accelerating drug discovery efforts by enabling the precise characterization of pharmacological interventions in real time. As technology continues to advance, leveraging RET-based sensors will undoubtedly continue to propel our quest to unravel the complexities of GPCR signaling and pave the way for novel therapeutic strategies. 1.      Gilman, A.G., G proteins: transducers of receptor-generated signals. Annu Rev Biochem, 1987. 56: p. 615-49. 2.      Zhou, Y., et al., Multiple GPCR Functional Assays Based on Resonance Energy Transfer Sensors. Front Cell Dev Biol, 2021. 9: p. 611443. 3.      Maziarz, M., et al., Revealing the Activity of Trimeric G-proteins in Live Cells with a Versatile Biosensor Design. Cell, 2020. 182(3): p. 770-785.e16. 4.      Salahpour, A., et al., BRET biosensors to study GPCR biology, pharmacology, and signal transduction. Frontiers in Endocrinology, 2012. 3. 5.      Zhao, P., et al., Activation of the GLP-1 receptor by a non-peptidic agonist. Nature, 2020. 577(7790): p. 432-436. 6.      Galés, C., et al., Real-time monitoring of receptor and G-protein interactions in living cells. Nat Methods, 2005. 2(3): p. 177-84. 7.      Wan, Q., et al., Mini G protein probes for active G protein-coupled receptors (GPCRs) in live cells. J Biol Chem, 2018. 293(19): p. 7466-7473. 8.      McNeill, S.M., et al., The role of G protein-coupled receptor kinases in GLP-1R β-arrestin recruitment and internalisation. Biochemical Pharmacology, 2024. 222: p. 116119. 9.      Olsen, R.H.J., et al., TRUPATH, an open-source biosensor platform for interrogating the GPCR transducerome. Nat Chem Biol, 2020. 16(8): p. 841-849. 10.    Namkung, Y., et al., Monitoring G protein-coupled receptor and β-arrestin trafficking in live cells using enhanced bystander BRET. Nature Communications, 2016. 7(1): p. 12178. 11.    Strungs, E.G., L.M. Luttrell, and M.H. Lee, Probing Arrestin Function Using Intramolecular FlAsH-BRET Biosensors. Methods Mol Biol, 2019. 1957: p. 309-322. 12.    Jiang, L.I., et al., Use of a cAMP BRET sensor to characterize a novel regulation of cAMP by the sphingosine 1-phosphate/G13 pathway. J Biol Chem, 2007. 282(14): p. 10576-84. 13.    Goyet, E., et al., Fast and high resolution single-cell BRET imaging. Sci Rep, 2016. 6: p. 28231. 14.    Pfleger, K.D., R.M. Seeber, and K.A. Eidne, Bioluminescence resonance energy transfer (BRET) for the real-time detection of protein-protein interactions. Nat Protoc, 2006. 1(1): p. 337-45. 15.    Janicot, R., et al., Direct interrogation of context-dependent GPCR activity with a universal biosensor platform. bioRxiv, 2024.

October 2022 β-arrestin1 and 2 exhibit distinct phosphorylation-dependent conformations when coupling advanced NanoLuc/FlAsH-based biosensors reveals distinct conformational signatures of β-arrestin1 and 2 when

activation initiates conformational changes, exposing an intracellular cavity (Kang, Y. et al. 2015, Chen F et al. 2021, Chen, H. et al. 2022). Recent years have seen cryo-EM dominate new GPCR structure determinations, offering insight into GPCR-effector Thus, exploring large-scale protein-protein interaction datasets could shed light on connections between

When comparing the CKRs structures complexes, the disulfide bridges formed between the N-loop and the agonist (maraviroc) (Tan, Zhu et al. 2013, Zheng, Han et al. 2017, Isaikina, Tsai et al. 2021, Zhang, Chen CCL15L (residues 26-92) and CCL15M (residues 27-92), while the third structure lacks a ligand (Shao, Shen conformational change of Y2917.43 tilted toward TM2, a model supported by mutagenesis experiments (Shao, Shen

Through developing a high-resolution method, Hao Chen et al. directly visualized the fusion of vesicles Shenoy, and R.J. Lefkowitz. 2006. Trafficking of G protein coupled receptors. Circ. Chen, X. Zhang, and L. Ma. 2008.

structures of B2R have provided molecular insights into the functions and regulation of B2R, which shed

Recent structural studies shed light on the molecular mechanisms involved in GPCR-arrestin coupling,

, provide insights into the unique and complex process of ligand dissociation from the receptor and shed

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However, what their particular function is, remains to be seen."

., 2003). β-arrestins, traditionally seen as terminators of G-protein signaling, are now recognised as The gravity of this regulation becomes even more apparent when we consider the potential consequences Wei, H., Ahn, S., Shenoy, S. K., Karnik, S. S., Hunyady, L., Luttrell, L. M., & Lefkowitz, R.

These findings shed light on a sophisticated signaling network directed by intestinal microbial metabolites

published S1PR structures in complex with antagonists and agonists, our structure with S1P5-inverse agonist sheds

In this aspect, our present data shed new light on the unexplored H2R signaling mechanisms.

the changed conformation of the receptor and consequently activated signaling pathways, and also may shed

advancements in the cellular biology of G protein-coupled receptors (GPCRs) about a novel biosensor shed When AUR is oxidized by APEX2 in the presence of H 2 O 2 , it produces a fluorescent product that can

This redundancy can be seen as problematic in drug discovery as blocking a single receptor might not Signaling bias can be seen as complex as advantageous since selectively inhibiting certain signaling the receptor and its existence as homo and herero-oligomeres at the cell surface should be considered when

this has the potential to enhance GPCR subtype-selectivity, it also presents a significant challenge when modulators (NAMs), that fully or partially dampen the receptor's functional response to the ligand (Wold, Chen selectivity, which can arise from greater sequence variation in allosteric sites among receptor subtypes when This is particularly important when dealing with receptor subtypes that exhibit significant similarity substantial doses of allosteric modulators with a diminished risk of target-related toxicity (Wold, Chen

When it comes to signal transduction, cellular context matters. Pharmaceuticals (Basel, Switzerland), 14(5), 439. https://doi.org/10.3390/ph14050439 Chen, K. Nature chemical biology, 5(10), 734–742. https://doi.org/10.1038/nchembio.206 Wei, H., Ahn, S., Shenoy

Suchismita Roy et al. have explored how growth factors can modulate canonical G protein signaling, shedding

The TM5 extension of receptors Gs-coupled provides unique interactions that are not seen in complexes

the scientist’s view: a conversation with … Chris Tate AI is dreaming up drugs that no one has ever seen

advancements in site-directed technology have largely supplanted random mutagenesis, the latter has seen

Azietaku for his first contributor article on Illuminating GPCR Research: FRET and BRET-Based Sensors Shed

and subsequent activation of the G-protein heterotrimeric complex (α, β, and γ); it is at this point when Liu-Chen, and J.R.

They shed light on the essential role of β-arrestin binding to the lipid bilayer for efficient interaction

When I started studying aGPCRs, the structural conformation of the GAIN domain of ADGRL1/Lphn1 and ADGRB3 of human ADGRL3-G13, this paper reports that the stalk peptide of ADGRL3 adopts a hook conformation when Furthermore, when an alignment analysis of the Stalk peptide of the aGPCR family was performed highlighted ., Zhu, X., Wang, N., Xu, Z., Xia, R., Liang, J., Duan, Y., Yin, H., Xiong, Y., Zhang, A., Guo, C., Chen

In general, signaling occurs when agonists engage key microswitch structures located in the TM domain surface area of ligand-receptor interface for these GPCRs makes modulation with small molecule drugs, when As seen below in Figure 1, natural ligands do not make use of all the potential binding contacts with great deal of scientific and business interest in solving this problem, and the last two years have seen