The lutropin/choriogonadotropin receptor (LHR) is a member of the rhodopsin-like subfamily of G protein coupled receptor (GPCRs), that has been shown to mediate the internalization of its two naturally occurring agonist, lutropin and choriogonadotropin (CG). The clustered agonist-receptor complex is internalized by a dynamin-dependent pathway and traverses the endosomal compartment without agonist dissociation Dissociation of the agonist-receptor complex occurs in the lysosomes, where both the agonist and receptor are degrade. Recently, constitutively activating mutations of the receptor have been identified that are associated with familial male-precocious puberty (FMPP). A FMPP is a form of sexual precocious puberty in boys in which testosterone levels are elevated independent of changes in luteinizing hormone-releasing hormone and serum luteinizing hormone levels, We have now analyzed two naturally occurring, constitutively active mutants of the human LHR. These mutations were introduced into the rat LHR (rLHR) and are designated L435R and D556Y. Cells expressing rLHR-D556Y bind human choriogonadotropin (hCG) with normal affinity, exhibit a 25-fold increase in basal cAMP and respond to hCG with a normal increase in cAMP accumulation. Cells expressing rLHR-L435R also bind hCG with normal affinity, exhibit a 47-fold increase in basal cAMP, and do not respond to hCG with a further increase in cAMP accumulation. This mutation enhances the internalization of the free and agonist-occupied receptors ~2- and ~17- fold, respectively We conclude that the state of activation of the rLHR can modulate its basal and/or agonist-stimulated internalization. Since the internalization of hCG is involved in the termination of hCG actions, we suggest that the lack of responsiveness detected in cells expressing rLHR-L435R is due to the fast rate of internalization of the bound hCG. The finding that membranes expressing rLHR-L435R respond to hCG with an increase in adenylyl cyclase activity supports this suggestion. Autonomous Leydig cell activity in FMPP is caused by a constitutively activating LH/CGR.

Based on the co-linearity in the Triticeae, comparative RFLP analysis of 2M chromosome of Ae. comosa Sibth et Sm. was performed with 2MS and 2M additional lines of Triticum aestivum L. cv. Chinese Spring. Among the wheat RFLP probes conserved in the short arms of wheat chromosome 2, those above psr912 were located on the long arms of 2M in Aegilops comosa. The rest probes on the short arm and all the probe sequences on the long arm of group 2 chromosome in wheat were conserved on the equivalent chromosomal position in Aegilops comosa. So, it is apparent that some chromosomal segment from the short arm had been transferred to long arm while reconstructing 2M chromosome relative to wheat chromosomes. The break-point was located between psr912 and psr131 of the short arm. This rearrangement of chromosome 2M might be a molecular evidence of the M genome speciation from an ancestral type.