earticle

영어

Equine-chorionic gonadotropin (eCG) is a member of the glycoprotein family with luteinizing hormone (LH), follicle stimulating hormone (FSH) and thyroid stimulating hormone (TSH). In non-equid species, eCG shows both LH- and FSH-like activities except the horses and has a high affinity for both FSH and LH receptors. These receptors were synthesized in granulosa/theca and Sertoli/Leydig cells in ovary/testis and transported to the membrane surface by agonist. Familial male precocious puberty (FMPP) is a gonadotropin-independent disorder that is inherited in an autosomal dominant, malelimited pattern. LH/CG receptor (LH/CGR), like the receptors for FSH and TSH, is a member of a superfamily of receptors which act via interactions with G-proteins. All of the receptors in this superfamily trasverse the plasma membrane with seven highly conserved a-helices oriented with an extracellular amino terminus and an intracellular carboxy terminus. To access the functional effect of the activation mutants (M398T, L457R D564G and D576Y) and inactivations (D383N, R464H and Y546F) in the eLH/CGR, wild type and mutated eLH/CGR were transiently expressed in CHO-K1 cells and cAMP accumulation was measured. rec-eCG, produced from CHO-K1 cells, was shown a dose-dependent increase in cAMP production in cells expressing the wild-type eLH/CGR, with an EC50 of 50.7 ng /mL and mean maximal stimulation (96.4±2.4 nM). In the basal cAMP production, the mutants were highly increased. eLH/CGR-D576Y and eLH/CGR-L457R stimulated a 8.3-fold and 13.6-fold increase in basal cAMP production in CHO-K1 cells, respectively. However, cAMP production in the M398T mutant was a significantly decreased than wild type eLH/ CGR. In the D564G, the basal cAMP production was shown 6.4 times higher than wild type eLH/CGR. In the inactivating mutants (D383N and R464H), cAMP responsiveness was completely flat. cAMP concentration in the Y546F was a little increased. In summary, we have identified four constitutively activating point mutations and 3 inactivating mutations of eLH/CGR that are responsible for constitutive activation and inactivation of CHO-K1 cells. Knowledge of those mutations will facilitate genetic counseling and diagnosis, as well as provide the basis to study the three-dimensional conformation of the receptor domains involved in ligand-binding and G protein activation.