Dihydromunduletone

Dihydromunduletone (DHM) is a rotenoid derivative and a selective, potent adhesion G protein-coupled receptor (aGPCR) (GPR56 and GPR114/ADGRG5) antagonist with an IC ₅₀ of 20.9 μM for GPR56, but not inhibit GPR110 or class A GPCRs^[1]. IC50 & Target:IC50: 20.9 μM (GPR56)^[1]; GPR114^[1] In Vitro:Assays are initiated by the addition of [³⁵S]GTPγS, and the rates of aGPCR-stimulated G protein activation ([³⁵S]GTPγS binding to Gα) are measured with or without the influence of added compounds. Dihydromunduletone (DHM) inhibits the kinetics of GPR56 7TM-stimulated G13 GTPγS binding to varying degrees. Dihydromunduletone is the best inhibitory compound and reduced the rate at which GPR56 7TM activated G13 >75% (from 0.18 to 0.04 minute ¹)^[1].
At a concentration of Dihydromunduletone (DHM) that maximally inhibits GPR56 (50 μM), the rate of GPR114 7TM-stimulated Gs activity is also inhibited dramatically. When Dihydromunduletone (50 μM) is applied to the GPR110 7TM, it fails to inhibit GPR110 stimulation of Gq GTPγS binding^[1].
Cells transfected with GPR56 A386M 7TM are incubated with increasing concentrations of Dihydromunduletone. P7 peptide agonist is added, and SRE-luciferase activity is measured. Dihydromunduletone inhibits the P7 peptide-induced luciferase activity in a concentration-dependent manner. Cells are also treated with a fixed concentration of 3 μM Dihydromunduletone and then stimulated with an increasing concentration of P7 peptide agonist. Dihydromunduletone treatment blunts P7 peptide activation at each concentration. In conclusion, Dihydromunduletone antagonizes synthetic-peptide agonist and tethered-peptide agonist-mediated aGPCR activation in isolated membranes and HEK293T cell-based assays, but it does not inhibit basal receptor signaling^[1].