Handbook of experimental pharmacology最新文献

G protein-coupled receptors (GPCRs) are highly dynamic membrane receptors with numerous subtypes and complex signal transduction pathways. Precise regulation of GPCR signaling is closely related to disease treatment but presents significant challenges with classical orthosteric ligands. Allosteric modulators, a class of emerging drug candidates, can selectively bind to the allosteric sites located outside the conserved orthosteric pocket. In particular, biased allosteric modulators (BAMs) can stabilize specific conformations of GPCRs to harness signal transduction with high selectivity and specificity, offering a novel approach to modulate GPCR pharmacology and develop safer therapeutic agents. In recent years, significant progress has been made in the study of GPCR allosteric modulation due to advancements in structural biology. However, knowledge about GPCR-biased allostery is still in its infancy. In this chapter, we present the most recent breakthroughs in the discovery of BAM binding site in GPCRs and provide structural insights into biased allostery of GPCR signaling.

G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors and the most prominent drug targets. GPCR-biased signaling exerts different functions through distinct downstream signaling pathways of receptor to maintain body homeostasis. Metabolism is the series of biochemical processes that occur within a living organism to maintain life. GPCR-biased signaling and metabolism exhibit bidirectional interplay. On the one hand, metabolites including short-chain fatty acids (SCFAs) and long-chain fatty acids (LCFAs) act as ligands inducing biased GPCRs signaling. On the other hand, activated GPCRs regulate diverse metabolic functions by biased signal sorting (G protein or β-arrestin-mediated). G protein signaling mainly mediates rapid metabolic reaction, and β-arrestin signaling mainly mediates sustained metabolic effects. In clinical drug applications, GPCR-biased drugs can revolutionize metabolic disease therapeutics by enabling pathway-selective drug design to enhance efficacy while reducing side effects. Thus, delving deeper into the relationship between GPCR-biased signaling and metabolism is of great importance in physiology, pathology, and pharmacology. A systematic exploration of biased signaling will enhance insights into GPCRs-metabolism interactions, aiding disease mechanism studies, drug discovery, and clinical treatment strategies.

Upon stimulation by endogenous ligands, G protein-coupled receptors (GPCRs) activate downstream signaling pathways through multiple mechanisms, including G protein subtypes, β-arrestins, and receptor-specific partners. Synthetic ligands may activate only a subset of these pathways, resulting in functional selectivity or signaling bias. Since not all signaling outputs are therapeutically desirable, there is pharmaceutical interest in exploiting biased signaling. Although much effort is focused on designing ligands to induce receptor conformations that result in signal bias, it is also true that cellular systems adapt dynamically in ways that tune receptor signaling, termed system bias. In this chapter, we provide evidence that posttranslational modification of receptor machinery by S-nitrosylation is an important regulator of system bias in GPCR signaling. S-nitrosylation has been reported to affect the function of multiple classes of GPCR signaling pathway components, including receptors, G proteins, G protein-coupled receptor kinases, β-arrestins, and others. Further, untargeted proteomic studies of S-nitrosylated proteins have identified over 60 GPCRs, most heterotrimeric G proteins, and numerous GPCR signaling components, hinting at a class effect and unifying mechanism to bias the functional repertoires of GPCRs in vivo. Thus, protein S-nitrosylation provides prototypic examples for how post-translational regulatory mechanisms bias GPCRs endogenously.

The μ-opioid receptor (μOR) is the primary drug target of opioid analgesics such as morphine and fentanyl. Activation of μORs in the central nervous system inhibits ascending pain signaling to the cortex, thereby producing analgesic effects. However, the clinical use of opioid analgesics is severely limited by adverse side effects, including respiratory depression, constipation, addiction, and the development of tolerance. μOR-mediated signaling involves both the G_i/o/z protein pathway and the β-arrestin1/2 pathway. Recent research has indicated that G protein-biased agonists, which preferentially activate the G_i/o/z pathway over the β-arrestin1/2 pathway, may provide effective analgesia with reduced side effects, thus offering improved therapeutic potential. In this chapter, we review the molecular basis of μOR-biased agonism. By integrating findings from structural and dynamic studies, we summarize the structure-bias relationships of various μOR agonists, aiming to provide valuable insights for the development of next-generation μOR-biased agonists.

Research conducted over the last 15 years indicates that cAMP is generated not just from the plasma membrane but also from intracellular compartments, particularly in endosomes, where receptors are redistributed during the endocytosis process. This review centers on the parathyroid hormone type 1 receptor (PTH₁R) as a model for a peptide hormone GPCRs that generates cAMP from various locations with distinct duration and pharmacological effectiveness. We discuss how structural dynamics simulations aid in designing ligands that induce cAMP location bias, ultimately answering how the spatiotemporal generation of cAMP affects pharmacological responses mediated by the PTH₁R.

G protein-coupled receptors (GPCRs) engage multiple transducers to regulate distinct physiological processes. These transducers include various G proteins subtypes, GPCR kinases (GRKs), and β-arrestins. In addition to promoting receptor desensitization, β-arrestins serve as scaffolds for signaling via non-G protein pathways. Biased signaling enables GPCRs to selectively engage specific transducers, typically through different conformational states of GPCRs. While significant focus has been placed on developing biased ligands that preferentially activate specific G proteins or β-arrestins, the strategy focused on modulating particular G protein subunits (Gα versus βγ) remains underexplored. Recently, members of the KCTD (potassium channel tetramerization domain-containing) family have emerged as critical regulators of GPCR signaling, particularly through their roles in mediating Gβγ degradation or uncoupling Gβγ from downstream effectors. This ability positions the KCTD family as potential targets for selectively modulating Gβγ signaling with minimal impact on Gα-mediated pathways. In this chapter, we introduce the KCTD family, summarize current knowledge of their role in GPCR signaling regulation, and highlight unsolved questions in existing models, along with directions for future research.

G protein-coupled receptor (GPCR) biased signaling has emerged as a transformative paradigm, reshaping both fundamental understanding of receptor biology and pharmacological intervention. Significant advances have been made in deciphering the mechanisms underlying biased signaling and in the development of ligands that selectively engage specific pathways. Here, we outline key future directions in GPCR biased signaling and ligand pharmacology including the biased signaling theories, structural insights, methodological innovations and ligand pharmacology theories. We hope that these perspectives will contribute to pharmacological research, drug R & D, and clinical drug research and promoting safer and more effective GPCR-targeted treatments for human diseases.

This chapter considers biased signaling as a natural function of G protein-coupled receptors (GPCRs) in the form of probe dependence. Thus, any ligand that changes the conformation of the receptor (agonist, antagonist, or allosteric modulator) has the potential to change the natural signaling of the receptor through unequal conformational alterations in the receptor structure. This gives an added dimension to agonist selectivity beyond extracellular recognition, namely the ability of agonists to emphasize certain signaling pathways in the cell at the expense of others. Given this, selectivity is discussed in terms of varying intrinsic efficacy and selective stabilization of receptor states with methods to detect and measure these effects. Last, the translation of in vitro to complex in vivo systems will be considered.

Allosteric modulation of G protein-coupled receptors (GPCRs) is emerging as a powerful approach in drug discovery, offering enhanced subtype selectivity and the ability to bias signaling toward therapeutically preferred pathways, thereby reducing off-target effects. While most approved GPCR drugs act via the orthosteric site, this approach often lacks subtype specificity and induces pleiotropic signaling that can compromise therapeutic efficacy. Orthosteric biased ligands have provided proof of concept for functional selectivity, yet their development has been limited by site homology and challenges in fine-tuning pathway specificity. In contrast, allosteric modulators (AMs) bind to spatially and structurally distinct, less conserved sites located across extracellular, transmembrane, and intracellular receptor domains. By stabilizing discrete receptor conformations, AMs can fine-tune transducer engagement and preferentially direct signaling toward either G protein or β-arrestin (βarr) pathway. Recent structural and biophysical studies have provided insights into how diverse AMs lock GPCRs in specific conformations and modulate signaling across receptor families. Taken together, these findings reflect a shift in GPCR pharmacology, driven by the convergence of biased signaling and allosteric modulation. Biased allosteric modulators (BAMs) represent a promising class of ligands that bind at allosteric sites and selectively tune signaling pathways by biasing orthosteric ligand-induced responses. This review outlines the principles of biased signaling and allosteric modulation and highlights strategies for designing BAMs for GPCRs. Identifying BAMs could revolutionize GPCR drug discovery by enabling pathway-specific precision therapeutics with improved efficacy and fewer side effects.

G protein-coupled receptors (GPCRs) are key mediators of cellular signaling, participating in various physiological and pathological processes. Emerging evidence reveals that GPCRs can form functional heterodimers, wherein two distinct receptor subtypes interact mutually to generate unique signaling complexes. GPCR heterodimers play a crucial role in modulating cellular responses and are involved in biased signaling, a phenomenon where receptor activation preferentially triggers specific intracellular pathways (e.g., G protein vs. β-arrestin pathways). In this review, we will explore the molecular mechanisms underlying GPCR heterodimerization and the modulation of biased signaling in heterodimers. We first discuss the assembly and activation mechanisms based on heterodimerization in Class C GPCRs. Furthermore, we explore the impact of receptor dimerization on downstream biased signaling and the physiological relevance of these heterodimers. Next, we also summarize three criteria and essential technologies for identifying potential heterodimers. Lastly, we address the challenges and future directions in the study of GPCR heterodimers, particularly for drug discovery, highlighting their potential in designing novel therapeutics with enhanced specificity and reduced side effects.