Promiscuity, pre-coupling and instability

doi:10.1016/S0165-6147(97)01150-4

Trends in Pharmacological Sciences

Volume 19, Issue 1, 1 January 1998, Page 13

https://doi.org/10.1016/S0165-6147(97)01150-4 Get rights and content

Abstract

Stabilization of active receptor states by G proteins produces effector-dependent agonist pharmacology

References (2)

P Leff
Trends Pharmacol. Sci.
(1997)
U Gethert
J. Biol. Chem.
(1997)

Cited by (15)

Resonance energy transfer-based approaches to study GPCRs
2016, Methods in Cell Biology
Citation Excerpt :
The question on how GPCR–G protein coupling occurs has been widely studied over the years. The initial model explaining the functioning of the GPCR–G protein complex has evolved considerably (Bourne, 1997; Limbird, 2004; Moreira, 2014; Strange, 2008b) and new concepts have emerged such as constitutive activity (Seifert & Wenzel-Seifert, 2002), precoupling and/or preassembly (Ayoub et al., 2007; Ayoub, Trinquet, Pfleger, & Pin, 2010; Gales et al., 2006; Leff & Scaramellini, 1998; Nobles, Benians, & Tinker, 2005; Qin, Dong, Wu, & Lambert, 2011), multiple coupling (Hamm, 1998; Hermans, 2003; Simon, Strathmann, & Gautam, 1991), functional selectivity (Kenakin, 2012; Rajagopal et al., 2010; Urban et al., 2007), and intracellular G protein activation (Irannejad et al., 2013; Koelle, 2006). The physical interaction and the functional coupling of GPCRs with their cognate heterotrimeric G proteins were initially studied using the GTPγS-binding assay (Senogles et al., 1987; Stadel, Shorr, Limbird, & Lefkowitz, 1981; Tian, Duzic, Lanier, & Deth, 1994) and biochemical techniques (Neumann et al., 2002; Smith & Limbird, 1981), and recently through crystallographic analysis (Kobilka & Schertler, 2008; Moreira, 2014; Rasmussen et al., 2011).
Since their discovery, G protein-coupled receptors (GPCRs) constitute one of the most studied proteins leading to important discoveries and perspectives in terms of their biology and implication in physiology and pathophysiology. This is mostly linked to the remarkable advances in the development and application of the biophysical resonance energy transfer (RET)-based approaches, including bioluminescence and fluorescence resonance energy transfer (BRET and FRET, respectively). Indeed, BRET and FRET have been extensively applied to study different aspects of GPCR functioning such as their activation and regulation either statically or dynamically, in real-time and intact cells. Consequently, our view on GPCRs has considerably changed opening new challenges for the study of GPCRs in their native tissues in the aim to get more knowledge on how these receptors control the biological responses. Moreover, the technological aspect of this field of research promises further developments for robust and reliable new RET-based assays that may be compatible with high-throughput screening as well as drug discovery programs.
Modelling of signalling via G-protein coupled receptors: Pathway-dependent agonist potency and efficacy
2003, Bulletin of Mathematical Biology
Citation Excerpt :
Other recent studies have also shown that both receptors and G-protein translocate either into or out of caveolae (a flask-shaped vesicle in cell membrane) as a response to activation and it is uncertain if the compartmentalization of the receptors and G-protein precedes activation or is a result of it; see, for examples, the reviews by Cordeaux and Hill (2002) and Ostrom (2002). In a review based on the three-state model, Leff and Scaramellini (1998) have suggested that the effect of pathway-dependent differences in agonist potency order may be explained by the compartmentalization of pathways, whereby one G-protein is isolated from the others and there is thus no competition for receptors between them. Although our present model is able to predict the pathway-dependent agonist potency and efficacy without putting any restriction on the movement of receptors and G-protein, significant changes in the agonist efficacy compared to the intact model, in particular, can be predicted if compartmentalization is incorporated.
A mathematical model is constructed to study promiscuous coupling of receptors to G-proteins and to simulate events leading to the activation of multiple effector pathways within a cell. The model is directed at a better understanding of the factors that determine the efficacy and potency of a drug. Assuming that the receptors can exist in multiple conformational states, and allowing for agonist specific conformation, a system of ordinary differential equations is constructed and subsequently pathway-dependent agonist efficacy and potency order is predicted. A simple case of the compartmentalization of receptors and G-proteins is also given, using the current model to illustrate the effects of spatial heterogeneity on the predicted response.
Biochemical and pharmacological control of the multiplicity of coupling at G-protein-coupled receptors
2003, Pharmacology and Therapeutics
For decades, it has been generally proposed that a given receptor always interacts with a particular GTP-binding protein (G-protein) or with multiple G-proteins within one family. However, for several G-protein-coupled receptors (GPCR), it now becomes generally accepted that simultaneous functional coupling with distinct unrelated G-proteins can be observed, leading to the activation of multiple intracellular effectors with distinct efficacies and/or potencies. Multiplicity in G-protein coupling is frequently observed in artificial expression systems where high densities of receptors are obtained, raising the question of whether such complex signalling reveals artefactual promiscuous coupling or is a genuine property of GPCRs. Multiple biochemical and pharmacological evidence in favour of an intrinsic property of GPCRs were obtained in recent studies. Thus, there are now many examples showing that the coupling to multiple signalling pathways is dependent on the agonist used (agonist trafficking of receptor signals). In addition, the different couplings were demonstrated to involve distinct molecular determinants of the receptor and to show distinct desensitisation kinetics. Such multiplicity of signalling at the level of G-protein coupling leads to a further complexity in the functional response to agonist stimulation of one of the most elaborate cellular transmission systems. Indeed, the physiological relevance of such versatility in signalling associated with a single receptor requires the existence of critical mechanisms of dynamic regulation of the expression, the compartmentalisation, and the activity of the signalling partners. This review aims at summarising the different studies that support the concept of multiplicity of G-protein coupling. The physiological and pharmacological relevance of this coupling promiscuity will be discussed.
Further delineation of the two binding sites (R*(n)) associated with tachykinin neurokinin-1 receptors using [3-prolinomethioninen<sup>11</sup>]SP analogues
1999, Journal of Biological Chemistry
Two binding sites are associated with neurokinin-1 substance P receptors in both transfected cells and mammalian tissues. To further delineate the interactions between the crucial C-terminal methionine of substance P and these two binding sites, we have incorporated newly designed constrained methionines, i.e. (2 S, 3 S)- and (2 S,3 R)-prolinomethionines. The potencies of these C terminus-modified SP analogues to bind both sites and to activate phosphatidylinositol hydrolysis and cAMP formation have been measured, together with those of their corresponding sulfoxides and sulfones. The molecular nature of these two binding sites and their selective coupling to effector signaling pathways are discussed in the light of current models of receptor activation. The less abundant binding site is coupled to G_q/11 proteins, whereas the most abundant one interacts with G_s proteins in Chinese hamster ovary cells transfected with human neurokinin-1 receptors. The specific orientation of the C-terminal methionine side chain imposed by these constraints shows that macroscopically χ₁ and χ₂ angles of this crucial C-terminal residue are similar in both binding sites. However, slight but significant variations in the rotation around the Cγ–S bond yield different either stabilizing or destabilizing interactions in the two binding sites. These results highlight the need of such constrained amino acids to probe subtle interactions in ligand-receptor complexes.
Principles of agonism: Undressing efficacy
1998, Trends in Pharmacological Sciences
Three-state and two-state models [1]
1998, Trends in Pharmacological Sciences

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Trends in Pharmacological Sciences

Promiscuity, pre-coupling and instability

Abstract

Trends Pharmacol. Sci.

J. Biol. Chem.