The role of kinetic context in apparent biased agonism at GPCRs

Abstract

Biased agonism describes the ability of ligands to stabilize different conformations of a GPCR linked to distinct functional outcomes and offers the prospect of designing pathway-specific drugs that avoid on-target side effects. This mechanism is usually inferred from pharmacological data with the assumption that the confounding influences of observational (that is, assay dependent) and system (that is, cell background dependent) bias are excluded by experimental design and analysis. Here we reveal that ‘kinetic context', as determined by ligand-binding kinetics and the temporal pattern of receptor-signalling processes, can have a profound influence on the apparent bias of a series of agonists for the dopamine D2 receptor and can even lead to reversals in the direction of bias. We propose that kinetic context must be acknowledged in the design and interpretation of studies of biased agonism.

Distinct Signaling Patterns of Allosteric Antagonism at the P2Y1 Receptor

“…from three independent experiments performed in duplicate. The K B values of MRS2500 and BPTU and slopes from Schild analysis from three separate experiments are listed in Table 1. residence time (Guo et al, 2014;Klein Herenbrink et al, 2016), signaling amplification (Hepler, 2014), probe dependence (Kenakin, 2008;Ehlert, 2013), and cell background (Kenakin, 2009), in addition to the possibility of the conformational selective antagonism of BPTU in different pathways (Edelstein and Changeux, 2016).…”

“…Regarding the molecular mechanisms of insurmountable antagonism, the slow dissociation of an antagonist-receptor complex or long residence time has been traditionally considered as a major mechanism (Guo et al, 2014;Klein Herenbrink et al, 2016). Allosteric sites, distinct conformations, and receptor internalization have also been used as alternative explanations.…”

How Oliceridine (TRV-130) Binds and Stabilizes a μ-Opioid Receptor Conformational State That Selectively Triggers G Protein Signaling Pathways

“…These states are hypothesized to modulate ligand binding kinetics, which was recently shown to play an important role in the profile of biased agonists. 49 Notably, one of the residues that stabilize one of these intermediate states along the ligand’s reactive binding pathway, specifically the residue at position 2.63, is different among all opioid receptor subtypes. This residue is an asparagine in the MOR, a valine in the KOR, and a lysine in the DOR.…”

Structure-Activity Analysis of Biased Agonism at the Human Adenosine A3 Receptor

“…These time-dependent processes are an important consideration, as signaling assays require different incubations times and therefore may be differentially influenced by A 3 AR desensitization and/or internalization. Future studies will also assess the binding kinetics of structurally distinct A 3 AR agonists, as it is becoming appreciated that the agonist residence time can influence the efficacy and bias profile observed (Sykes et al, 2009;Guo et al, 2012;Klein Herenbrink, 2016).…”