Unifying Family A GPCR Theories of Activation

Tehan, Benjamin G.; Bortolato, Andrea; Blaney, Frank E.; Weir, Malcolm; Mason, Jonathan S.

doi:10.1016/j.pharmthera.2014.02.004

Cited by 178 publications

(223 citation statements)

References 74 publications

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“…S5). The above features appear to be characteristic of the rhodopsin family of GPCRs based on the available crystal structures (43). Not seen in the crystal structure of active rhodopsin is that, in a native-like phospholipid environment at low pH where MIIbH + is strongly enriched, the fully activated receptor is apparently in equilibrium between multiple conformations of comparable populations defined by the positions of TM6 and TM7 at the cytoplasmic surface.…”

Section: Discussionmentioning

confidence: 97%

Conformational equilibria of light-activated rhodopsin in nanodiscs

Eps

Lydia

Morizumi

et al. 2017

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

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Conformational equilibria of G-protein-coupled receptors (GPCRs) are intimately involved in intracellular signaling. Here conformational substates of the GPCR rhodopsin are investigated in micelles of dodecyl maltoside (DDM) and in phospholipid nanodiscs by monitoring the spatial positions of transmembrane helices 6 and 7 at the cytoplasmic surface using site-directed spin labeling and double electron-electron resonance spectroscopy. The photoactivated receptor in DDM is dominated by one conformation with weak pH dependence. In nanodiscs, however, an ensemble of pH-dependent conformational substates is observed, even at pH 6.0 where the MIIbH + form defined by proton uptake and optical spectroscopic methods is reported to be the sole species present in native disk membranes. In nanodiscs, the ensemble of substates in the photoactivated receptor spontaneously decays to that characteristic of the inactive state with a lifetime of ∼16 min at 20°C. Importantly, transducin binding to the activated receptor selects a subset of the ensemble in which multiple substates are apparently retained. The results indicate that in a native-like lipid environment rhodopsin activation is not analogous to a simple binary switch between two defined conformations, but the activated receptor is in equilibrium between multiple conformers that in principle could recognize different binding partners.G -protein-coupled receptors (GPCRs) are central components of protein-protein interaction networks and can serve as hubs that link the extracellular environment of cells to intracellular signaling events (1). As such, they interact with several intracellular proteins (i.e., arrestins, G proteins, kinases). To obtain such diversity in molecular interaction, GPCRs are thought to be in equilibrium between multiple conformations at the cytoplasmic surface (2-4), enabling conformation-dependent interactions with different partners.The rod photoreceptor rhodopsin has served as a model for members in the class A family of GPCRs. In native membranes (5-7) and reconstituted liposomes (8, 9), photoactivated rhodopsin within milliseconds reaches a pH-dependent quasi-equilibrium between states designated MI and MII, which are distinguished by their optical absorbance maxima and signature absorbances in the infrared (10-12). The optically identified MII state has been found to consist of isochromic substates, namely MIIa, MIIb, and MIIbH + (13-15) (Fig. 1A). MIIbH + , populated at pH 6.0, is thought to be the functionally active substate that recognizes the cognate G-protein transducin (8,15,16).Early data relating global protein structural changes to activation in a GPCR were provided by continuous wave (CW) sitedirected spin labeling (SDSL)-Electron Paramagnetic Resonance (EPR) studies in rhodopsin, where it was shown that a generally outward motion of TM6 and a smaller inward motion of TM7 at the cytoplasmic surface were hallmarks of activation in dodecyl maltoside (DDM) micelles (17, 18). High-resolution distance mapping with SDSL and double electron...

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Section: Discussionmentioning

confidence: 97%

Conformational equilibria of light-activated rhodopsin in nanodiscs

Eps

Lydia

Morizumi

et al. 2017

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

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“…Extracellular Signal-Regulated Kinase-1/2/ArrestinMediated Biased Agonism. The concept of biased agonism, by which a certain modified analog ligand for a given receptor activates a signaling pathway cascade that is distinct from that activated by the nonmodified ligand is drawing considerable attention in the GPCR field, in part because it potentially offers a means to develop novel therapeutics that selectively induce only desirable responses in the target system (Reiter et al, 2012;Luttrell, 2014;Tehan et al, 2014). Moreover, because the PTHR1 can signal through multiple pathways, ligands that selectively activate one pathway but not the others could help in determining which signaling pathways contribute to the biologic responses induced by PTH ligands in bone and kidney target cells.…”

Section: A G Protein Coupling and Signal Regulationmentioning

confidence: 99%

International Union of Basic and Clinical Pharmacology. XCIII. The Parathyroid Hormone Receptors—Family B G Protein–Coupled Receptors

2015

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“…Consistently with their proposed role in keeping the receptor in the inactive conformation, mutations that disrupt this network often result in constitutively active receptors (examples are discussed in Ref. 30).…”

Section: Key Features Of Gpcr Structures Relevant To Drug Discoverymentioning

confidence: 64%

“…These structures also revealed the outward movement of TM6, although the extent of this movement was larger than that observed in the opsin structure. Drawing on the information from these receptor systems and the wealth of receptor mutagenesis data, it is possible to propose a common activation mechanism (30). Central to this mechanism is a set of conserved residues in the core of the receptors consisting of Leu 3.43 , Phe 6.44 , and X to hydrogen-bond with Tyr 5.58 via a water molecule, which facilitates its interaction with Arg 3.50 of the so-called ionic lock motif of the (D/E)RY.…”

Section: Key Features Of Gpcr Structures Relevant To Drug Discoverymentioning

confidence: 99%

“…Each receptor system with its unique agonist molecule and binding site will effect the changes required for receptor activation differently. For example, in the case of the ␤ 2 -adrenergic receptor, agonists form hydrogen bonds with two serine residues on TM5 (Ser (30). An interesting observation from the resolution of the related turkey ␤ 1 -adrenergic receptor in complex with a range of full and partial agonists revealed how differential ligand efficacies might be rationalized from structural insight.…”

Section: Key Features Of Gpcr Structures Relevant To Drug Discoverymentioning

confidence: 99%

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From G Protein-coupled Receptor Structure Resolution to Rational Drug Design

Jazayeri

Dias

Marshall

2015

Journal of Biological Chemistry

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A number of recent technical solutions have led to significant advances in G protein-coupled receptor (GPCR) structural biology. Apart from a detailed mechanistic view of receptor activation, the new structures have revealed novel ligand binding sites. Together, these insights provide avenues for rational drug design to modulate the activities of these important drug targets. The application of structural data to GPCR drug discovery ushers in an exciting era with the potential to improve existing drugs and discover new ones. In this review, we focus on technical solutions that have accelerated GPCR crystallography as well as some of the salient findings from structures that are relevant to drug discovery. Finally, we outline some of the approaches used in GPCR structure based drug design.The process of drug discovery from bench to market is a high risk long term investment that has been estimated to cost about $1.8 billion per drug (1). Such high costs coupled with the pressure of patent expiry dates and increased regulatory constraints have propelled the pharmaceutical industry to increase efficiency of research and development to reduce the attrition rate. A key area of focus has been improvements in the quality of compounds that are discovered in the early stages of the drug discovery pipeline. The main driver for this effort has been the general observation that the hits identified from cell-based high throughput screening (HTS) 2 strategies are usually large lipophilic molecules that are difficult to optimize and carry a number of liabilities that significantly increase their failure rate (2). One of the main advances to tackle these issues has been the utilization of fragment-based drug discovery (FBDD) approaches that rely on screening small chemical fragments (100 -250 Da). Because of their small size, a significantly larger portion of chemical space can be explored with fewer compounds when compared with HTS. In addition, initial hits from a fragment screen bind more efficiently to their target and represent excellent starting points for medicinal chemists to grow and optimize these into lead and candidate molecules (3). The initial fragment hits exhibit low affinity, so they need to be screened at high concentrations that make them incompatible with biological assays. Instead, biophysical assays are used in FBDD cascades, and in addition, these approaches are combined with structural information derived primarily from x-ray crystallography. The application of structure-based drug design (SBDD) allows medicinal chemists to rationally convert fragment hits into larger compounds with higher affinity while maintaining the efficiency of binding and drug-like properties. Historically, SBDD methods gained traction with soluble proteins such as enzymes as routine generation of structural data is facilitated by their high stability in purified form (4 -6). This is in sharp contrast to membrane proteins such as G proteincoupled receptors (GPCRs) that have been refractory to SBDD due to the challenges associate...

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Unifying Family A GPCR Theories of Activation

Cited by 178 publications

References 74 publications

Conformational equilibria of light-activated rhodopsin in nanodiscs

Conformational equilibria of light-activated rhodopsin in nanodiscs

International Union of Basic and Clinical Pharmacology. XCIII. The Parathyroid Hormone Receptors—Family B G Protein–Coupled Receptors

From G Protein-coupled Receptor Structure Resolution to Rational Drug Design

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