Probing the Structural Determinants for the Function of Intracellular Loop 2 in Structurally Cognate G-Protein-Coupled Receptors

Drugs targeting the orthosteric, primary binding site of G protein–coupled receptors are the most common therapeutics. Allosteric binding sites, elsewhere on the receptors, are less well-defined, and so less exploited clinically. We report the crystal structure of the prototypic β2-adrenergic receptor in complex with an orthosteric agonist and compound-6FA, a positive allosteric modulator of this receptor. It binds on the receptor’s inner surface in a pocket created by intracellular loop 2 and transmembrane segments 3 and 4, stabilizing the loop in an α-helical conformation required to engage the G protein. Structural comparison explains the selectivity of the compound for β2- over the β1-adrenergic receptor. Diversity in location, mechanism, and selectivity of allosteric ligands provides potential to expand the range of receptor drugs.

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A complex structure of arrestin-2 bound to a G protein-coupled receptor

10.1101/822957 ◽

2019 ◽

Author(s):

Wanchao Yin ◽

Zhihai Li ◽

Mingliang Jin ◽

Yu-Ling Yin ◽

Parker W. de Waal ◽

...

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

G Protein ◽

Complex Structure ◽

Transmembrane Helix ◽

G Protein Coupled Receptors ◽

Dynamics Simulation ◽

Intracellular Loop ◽

Neurotensin Receptor 1 ◽

G Protein Coupled

AbstractArrestins comprise a family of signal regulators of G-protein-coupled receptors (GPCRs), which include arrestins 1 to 4. While arrestins 1 and 4 are visual arrestins dedicated to rhodopsin, arrestins 2 and 3 (Arr2 and Arr3) are β-arrestins known to regulate many nonvisual GPCRs. The dynamic and promiscuous coupling of Arr2 to nonvisual GPCRs has posed technical challenges to tackle the basis of arrestin binding to GPCRs. Here we report the structure of Arr2 in complex with neurotensin receptor 1 (NTSR1), which reveals an overall assembly that is strikingly different from the visual arrestin-rhodopsin complex by a 90° rotation of Arr2 relative to the receptor. In this new configuration, intracellular loop 3 (ICL3) and transmembrane helix 6 (TM6) of the receptor are oriented toward the N-terminal domain of the arrestin, making it possible for GPCRs that lack the C-terminal tail to couple Arr2 through their ICL3. Molecular dynamics simulation and crosslinking data further support the assembly of the Arr2–NTSR1 complex. Sequence analysis and homology modeling suggest that the Arr2–NTSR1 complex structure may provide an alternative template for modeling arrestin-GPCR interactions.

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Structural determinants involved in the activation and regulation of G protein-coupled receptors: lessons from the alpha1-adrenegic receptor subtypes

Biology of the Cell ◽

10.1111/j.1768-322x.2004.tb01422.x ◽

2004 ◽

Vol 96 (5) ◽

pp. 327-333 ◽

Cited By ~ 11

Author(s):

Susanna Cotecchia ◽

Laura Stanasila ◽

Dario Diviani ◽

Katja Björklöf ◽

Olivier Rossier ◽

...

Keyword(s):

G Protein ◽

G Protein Coupled Receptors ◽

Receptor Subtypes ◽

Structural Determinants ◽

G Protein Coupled

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Steroid and G Protein Binding Characteristics of the Seatrout and Human Progestin Membrane Receptor α Subtypes and Their Evolutionary Origins

Endocrinology ◽

10.1210/en.2006-0974 ◽

2007 ◽

Vol 148 (2) ◽

pp. 705-718 ◽

Cited By ~ 190

Author(s):

Peter Thomas ◽

Y. Pang ◽

J. Dong ◽

P. Groenen ◽

J. Kelder ◽

...

Keyword(s):

G Protein ◽

Hormone Receptors ◽

G Protein Coupled Receptors ◽

Spotted Seatrout ◽

Immunocytochemical Staining ◽

Intracellular Loop ◽

Binding Characteristics ◽

Protein Activation ◽

Gi Protein ◽

G Protein Coupled

A novel progestin receptor (mPR) with seven-transmembrane domains was recently discovered in spotted seatrout and homologous genes were identified in other vertebrates. We show that cDNAs for the mPR α subtypes from spotted seatrout (st-mPRα) and humans (hu-mPRα) encode progestin receptors that display many functional characteristics of G protein-coupled receptors. Flow cytometry and immunocytochemical staining of whole MDA-MB-231 cells stably transfected with the mPRαs using antibodies directed against their N-terminal regions show the receptors are localized on the plasma membrane and suggest the N-terminal domain is extracellular. Both recombinant st-mPRα and hu-mPRα display high affinity (Kd 4.2–7.8 nm), limited capacity (Bmax 0.03–0.32 nm), and displaceable membrane binding specific for progestins. Progestins activate a pertussis toxin-sensitive inhibitory G protein (Gi) to down-regulate membrane-bound adenylyl cyclase activity in both st-mPRα- and hu-mPRα-transfected cells. Coimmunoprecipitation experiments demonstrate the receptors are directly coupled to the Gi protein. Similar to G protein-coupled receptors, dissociation of the receptor/G protein complex results in a decrease in ligand binding to the mPRαs and mutation of the C-terminal, and third intracellular loop of st-mPRα causes loss of ligand-dependent G protein activation. Phylogenetic analysis indicates the mPRs are members of a progesterone and adipoQ receptor (PAQR) subfamily that is only present in chordates, whereas other PAQRs also occur in invertebrates and plants. Progesterone and adipoQ receptors are related to the hemolysin3 family and have origins in the Eubacteria. Thus, mPRs arose from Eubacteria independently from members of the GPCR superfamily, which arose from Archeabacteria, suggesting convergent evolution of seven-transmembrane hormone receptors coupled to G proteins.

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