In Silico Small Molecule Allosteric Antagonists of Thyroid-Stimulating Hormone Receptor

Introduction/Objective: Graves’ disease is an autoimmune disease characterized by overproduction of thyroid stimulating hormones that materialize into heat intolerance, tremors, weight loss, rapid heartbeat, among many other symptoms. Through overproduction of thyroid stimulating hormones, the thyroid stimulating hormone receptor (TSH-R) is overstimulated, resulting in the generation of TSH-R specific antibodies that initiate the autoimmune response. Recently, the cryo-EM structure of TSH-R was solved, revealing the active and inactive states and illuminating a hinge region in the receptor that facilitates movement between them.

Methods: PASSER pocket finding was used to investigate new allosteric sites in the hinge region to stabilize TSH-R in its inactive form. Additionally, molecular docking with SwissDock was used to dock drug-like molecules into the identified pocket. Chemical structures were then explored using fragment-based and rational drug design approaches.

Results/Discussion: Molecules with highly favorable AC Scores (<-300 kcal/mol) were identified as potential TSH-R binders to the hinge region of the inactive receptor. A class of molecules, di(1,3,5-triazin-2-yl)methane, emerged with superior binding affinity, with the optimal binder possessing an AC Score of -354 kcal/mol. Moreover, a fluorescent probe was designed to target the region with an AC Score of -380 kcal/mol.

Conclusion: Here, we identified a new allosteric pocket in the inactive TSH-R. Using molecular docking, we identified potential binders for this region that could exhibit allosteric antagonism of the Graves’ disease target. We have also proposed a new fluorescent probe to aid in further investigation of TSH-R activity.