Identification of Asn289 as a Ligand Binding Site in the Rat Thyrotropin-Releasing Hormone (TRH) Receptor As Determined by Complementary Modifications in the Ligand and Receptor: A New Model for TRH Binding

Biochemistry ◽  
1995 ◽  
Vol 34 (41) ◽  
pp. 13412-13422 ◽  
Author(s):  
Bomie Han ◽  
Armen H. Tashjian
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Thyrotropin Releasing Hormone ◽  
Ligand Binding Site ◽  
New Model ◽  
Releasing Hormone ◽  
Trh Receptor

scholarly journals The Antagonist pGlu-βGlu-Pro-NH2 Binds to an Allosteric Site of the Thyrotropin-Releasing Hormone Receptor

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5397
Author(s):  
Daniel L. De La Cruz ◽  
Laszlo Prokai ◽  
Katalin Prokai-Tatrai
Keyword(s):  
Binding Site ◽  
Homology Model ◽  
Thyrotropin Releasing Hormone ◽  
Allosteric Site ◽  
Releasing Hormone ◽  
Surface Recognition ◽  
Extracellular Loops ◽  
Binding Pockets ◽  
Central Actions ◽  
Trh Receptor

After we identified pGlu-βGlu-Pro-NH2 as the first functional antagonist of the cholinergic central actions of the thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH2), we became interested in finding the receptor-associated mechanism responsible for this antagonism. By utilizing a human TRH receptor (hTRH-R) homology model, we first refined the active binding site within the transmembrane bundle of this receptor to enhance TRH’s binding affinity. However, this binding site did not accommodate the TRH antagonist. This prompted us to consider a potential allosteric binding site in the extracellular domain (ECD). Searches for ECD binding pockets prompted a remodeling of the extracellular loops and the N-terminus. We found that different trajectories of ECDs produced novel binding cavities that were then systematically probed with TRH, as well as its antagonist. This led us to establish not only a surface-recognition binding site for TRH, but also an allosteric site that exhibited a selective and high-affinity binding for pGlu-βGlu-Pro-NH2. The allosteric binding of this TRH antagonist is more robust than TRH’s binding to its own active site. The findings reported here may shed light on the mechanisms and the multimodal roles by which the ECD of a TRH receptor is involved in agonist and/or antagonist actions.

Constraints of Opsin Structure on the Ligand-binding Site: Studies with Ring-fused Retinals¶

2002 ◽  
Vol 76 (6) ◽  
pp. 606 ◽  
Author(s):  
Takahiro Hirano ◽  
In Taek Lim ◽  
Don Moon Kim ◽  
Xiang-Guo Zheng ◽  
Kazuo Yoshihara ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Ligand Binding Site

1,25-Dihydroxyvitamin D3-induced upregulation of the thyrotropin-releasing hormone receptor in clonal rat pituitary GH3 cells

1995 ◽  
Vol 147 (3) ◽  
pp. 397-404 ◽  
Author(s):  
L M Atley ◽  
N Lefroy ◽  
J D Wark
Keyword(s):  
Vitamin D ◽  
Fold Increase ◽  
Thyrotropin Releasing Hormone ◽  
Gh3 Cells ◽  
Pituitary Hormone ◽  
Pituitary Cells ◽  
Hormone Production ◽  
Releasing Hormone ◽  
Rat Pituitary ◽  
Trh Receptor

Abstract 1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) is active in primary dispersed and clonal pituitary cells where it stimulates pituitary hormone production and agonist-induced hormone release. We have studied the effect of 1,25-(OH)2D3 on thyrotropin-releasing hormone (TRH) binding in clonal rat pituitary tumour (GH3) cells. Compared with vehicle-treated cells, 1,25-(OH)2D3 (10 nmol/l) increased specific [3H]MeTRH binding by 26% at 8 h, 38% at 16 h, 35% at 24 h and reached a maximum at 48 h (90%). In dose–response experiments, specific [3H]MeTRH binding increased with 1,25-(OH)2D3 concentration and reached a maximum at 10 nmol/l. Half-maximal binding occurred at 0·5 nmol 1,25-(OH)2D3/l. The vitamin D metabolite, 25-OH D3, increased [3H]MeTRH binding but was 1000-fold less potent than 1,25-(OH)2D3. In equilibrium binding assays, treatment with 10 nmol 1,25-(OH)2D3/l for 48 h increased the maximum binding from 67·4 ± 8·8 fmol/mg protein in vehicle-treated cells to 96·7 ± 12·4 fmol/mg protein in treated cells. There was no difference in apparent Kd (1·08 ± 0·10 nmol/l for 1,25-(OH)2D3-treated and 0·97 ± 0·11 nmol/l for vehicle-treated cells). Molecular investigations revealed that 10 nmol 1,25-(OH)2D3/l for 24 h caused an 8-fold increase in TRH receptor-specific mRNA. Actinomycin D (2 μg/ml, 6 h) abrogated the 1,25-(OH)2D3-induced increase in [3H]MeTRH binding. Cortisol also increased [3H]MeTRH binding but showed no additivity or synergism with 1,25-(OH)2D3. TRH-stimulated prolactin release was not enhanced by 1,25-(OH)2D3. We conclude that the active vitamin D metabolite, 1,25-(OH)2D3, caused a time- and dose-dependent increase in [3H]MeTRH binding. The effect was vitamin D metabolite-specific and resulted from an upregulation of the TRH receptor. Further studies are needed to determine the functional significance of this novel finding. Journal of Endocrinology (1995) 147, 397–404

Capturing of the free cysteine residue in the ligand-binding site by affinity labeling of the ORL1 nociceptin receptor

2011 ◽  
Vol 19 (24) ◽  
pp. 7597-7602 ◽  
Author(s):  
Ayami Matsushima ◽  
Hirokazu Nishimura ◽  
Shogo Inamine ◽  
Shiho Uemura ◽  
Yasuyuki Shimohigashi
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Cysteine Residue ◽  
Affinity Labeling ◽  
Ligand Binding Site ◽  
Nociceptin Receptor
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