Conformational restriction of G‐proteins Coupled Receptors (GPCRs) upon complexation to G‐proteins: A putative activation mode of GPCRs?

Louet, Maxime; Karakaş, Esra; Perret, Alexandre; Pérahia, David; Martinez, Jean; Floquet, Nicolas

doi:10.1016/j.febslet.2013.06.052

Cited by 11 publications

(11 citation statements)

References 43 publications

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“…S3). All of the foregoing experiments were carried out in the presence of the Gα q β 1 γ 2 trimer, because this affects the receptor conformational transitions (10,26), and thus its influence should be taken into account.…”

Section: Resultsmentioning

confidence: 99%

Ghrelin receptor conformational dynamics regulate the transition from a preassembled to an active receptor:Gq complex

Damian

Mary

Maingot

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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118

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How G protein-coupled receptor conformational dynamics control G protein coupling to trigger signaling is a key but still open question. We addressed this question with a model system composed of the purified ghrelin receptor assembled into lipid discs. Combining receptor labeling through genetic incorporation of unnatural amino acids, lanthanide resonance energy transfer, and normal mode analyses, we directly demonstrate the occurrence of two distinct receptor:Gq assemblies with different geometries whose relative populations parallel the activation state of the receptor. The first of these assemblies is a preassembled complex with the receptor in its basal conformation. This complex is specific of Gq and is not observed with Gi. The second one is an active assembly in which the receptor in its active conformation triggers G protein activation. The active complex is present even in the absence of agonist, in a direct relationship with the high constitutive activity of the ghrelin receptor. These data provide direct evidence of a mechanism for ghrelin receptor-mediated Gq signaling in which transition of the receptor from an inactive to an active conformation is accompanied by a rearrangement of a preassembled receptor:G protein complex, ultimately leading to G protein activation and signaling.GPCR | G protein | preassembly | conformation dynamics | signaling G protein-coupled receptors (GPCRs), one of the largest cell surface receptor families, are involved in many cellular signaling processes (1). Based on this property, as well as their importance as drug targets, the molecular aspects of GPCR functioning have been extensively investigated. In particular, coupling to heterotrimeric G proteins has been the focus of numerous studies. Indeed, delineating the molecular mechanisms responsible for receptor:G protein interaction is absolutely required to better understand how signaling is controlled. Recent years have seen spectacular advances that have culminated in elucidation of the 3D structure of the β 2 -adrenergic receptor:Gs complex (2). Nevertheless, the need for further progress remains, in particular to fully understand the dynamics of this interaction. This is a crucial question, given that how the receptor interacts with its G protein partner governs signaling, and thus biological and pathophysiological responses.To date, two different models for GPCR:G protein interaction have been proposed: collision coupling and preassembly. Originally, it was proposed that receptors and G proteins couple by collision (3, 4). One of the main features of this model is that only activated receptors interact with G proteins. Since then, alternative models of signaling have been developed. One of these, the preassembly model, proposes that the receptor and the G protein make a complex even in the absence of agonist (5-8).

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Section: Resultsmentioning

confidence: 99%

Ghrelin receptor conformational dynamics regulate the transition from a preassembled to an active receptor:Gq complex

Damian

Mary

Maingot

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

118

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“…The dynamics of GPCRs and the effect of ligands upon their conformational equilibria have been extensively investigated 4–8 . Computational approaches, including molecular dynamics simulations (conventional as well as enhanced sampling schemes), have contributed to provide a clearer picture of (1) the activation process and (2) the response of GPCRs to different types of ligands (agonists, antagonists or inverse agonists) 9–13 . The simulations have benefited enormously from the structural data accumulated in recent years, that culminated in the structural resolution of complexes formed by the GPCR bound to different heterotrimeric G proteins 14–17 .…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of the Allosteric Modulation of the Adenosine A2a Receptor by a Mini-G Protein

Renault

Louet

Marie

et al. 2019

Sci Rep

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Through their coupling to G proteins, G Protein-Coupled Receptors (GPCRs) trigger cellular responses to various signals. Some recent experiments have interestingly demonstrated that the G protein can also act on the receptor by favoring a closed conformation of its orthosteric site, even in the absence of a bound agonist. In this work, we explored such an allosteric modulation by performing extensive molecular dynamics simulations on the adenosine A2 receptor ( A 2 a R) coupled to the Mini-Gs protein. In the presence of the Mini-Gs, we confirmed a restriction of the receptor’s agonist binding site that can be explained by a modulation of the intrinsic network of contacts of the receptor. Of interest, we observed similar effects with the C-terminal helix of the Mini-Gs, showing that the observed effect on the binding pocket results from direct local contacts with the bound protein partner that cause a rewiring of the whole receptor’s interaction network.

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“…While low-frequency modes are generally associated with biological activity, the second order approximation underlying NMA limits its ability to access conformational substates and observe larger, diffusional motions. Nonetheless, NMAs are enormously successful and have, for instance, proposed GPCR activation mechanisms [ 12 ]. Combined with short MD trajectories NMA also predicted a molecular mechanism for GDP release from Gi [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Nullspace Sampling with Holonomic Constraints Reveals Molecular Mechanisms of Protein Gαs

Pachov

Bedem

2015

PLoS Comput Biol

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Proteins perform their function or interact with partners by exchanging between conformational substates on a wide range of spatiotemporal scales. Structurally characterizing these exchanges is challenging, both experimentally and computationally. Large, diffusional motions are often on timescales that are difficult to access with molecular dynamics simulations, especially for large proteins and their complexes. The low frequency modes of normal mode analysis (NMA) report on molecular fluctuations associated with biological activity. However, NMA is limited to a second order expansion about a minimum of the potential energy function, which limits opportunities to observe diffusional motions. By contrast, kino-geometric conformational sampling (KGS) permits large perturbations while maintaining the exact geometry of explicit conformational constraints, such as hydrogen bonds. Here, we extend KGS and show that a conformational ensemble of the α subunit Gαs of heterotrimeric stimulatory protein Gs exhibits structural features implicated in its activation pathway. Activation of protein Gs by G protein-coupled receptors (GPCRs) is associated with GDP release and large conformational changes of its α-helical domain. Our method reveals a coupled α-helical domain opening motion while, simultaneously, Gαs helix α5 samples an activated conformation. These motions are moderated in the activated state. The motion centers on a dynamic hub near the nucleotide-binding site of Gαs, and radiates to helix α4. We find that comparative NMA-based ensembles underestimate the amplitudes of the motion. Additionally, the ensembles fall short in predicting the accepted direction of the full activation pathway. Taken together, our findings suggest that nullspace sampling with explicit, holonomic constraints yields ensembles that illuminate molecular mechanisms involved in GDP release and protein Gs activation, and further establish conformational coupling between key structural elements of Gαs.

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Conformational restriction of G‐proteins Coupled Receptors (GPCRs) upon complexation to G‐proteins: A putative activation mode of GPCRs?

Cited by 11 publications

References 43 publications

Ghrelin receptor conformational dynamics regulate the transition from a preassembled to an active receptor:Gq complex

Ghrelin receptor conformational dynamics regulate the transition from a preassembled to an active receptor:Gq complex

Molecular Dynamics Simulations of the Allosteric Modulation of the Adenosine A2a Receptor by a Mini-G Protein

Nullspace Sampling with Holonomic Constraints Reveals Molecular Mechanisms of Protein Gαs

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