Position of Pro and Ser near Glu7.32 in the extracellular loop 3 of mammalian and nonmammalian gonadotropin-releasing hormone (GnRH) receptors is a critical determinant for differential ligand selectivity for mammalian GnRH and chicken GnRH-II
ABSTRACT A Glu/Asp7.32 residue in the extracellular loop 3 of the mammalian GnRH receptor (GnRHR) is known to interact with Arg8 of mammalian GnRH (mGnRH), which may confer preferential ligand selectivity for mGnRH than for chicken GnRH-II (cGnRH-II). However, some nonmammalian GnRHRs also have the Glu/Asp residue at the same position, yet respond better to cGnRH-II than mGnRH. Amino acids flanking Glu/Asp7.32 are differentially arranged such that mammalian and nonmammalian GnRHRs have an S-E/D-P motif and P-X-S/Y motif, respectively. We presumed the position of Ser7.31 or Pro7.33 of rat GnRHR as a potential determinant for ligand selectivity. Either placing Pro before Glu7.32 or placing Ser after Glu7.32 significantly decreased the sensitivity and/or efficacy for mGnRH, but slightly increased that for cGnRH-II in several mutant receptors. Among them, those with a PEV, PES, or SES motif exhibited a marked decrease in sensitivity for mGnRH such that cGnRH-II had a higher potency than mGnRH, showing a reversed preferential ligand selectivity. Chimeric mGnRHs in which positions 5, 7, and/or 8 were replaced by those of cGnRH-II revealed a greater ability to activate these mutant receptors than mGnRH, whereas they were less potent to activate wild-type rat GnRHR than mGnRH. Interestingly, a mutant bullfrog type I receptor with the SEP motif exhibited an increased sensitivity for mGnRH but a decreased sensitivity for cGnRH-II. These results indicate that the position of Pro and Ser near Glu7.32 in the extracellular loop 3 is critical for the differential ligand selectivity between mammalian and nonmammalian GnRHRs.
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- "Representative sequences of non-mammalian type I GnRH-Rs (mouse and human) and amphibian type I, II, and III GnRH-Rs (bullfrog) were compared with the three identified GnRH receptors in the lamprey (Flanagan et al., 1994, 1999; Zhou et al., 1994, 1995; Arora et al., 1995, 1997; Davidson et al., 1996; Ballesteros et al., 1998; Myburgh et al., 1998; Chung et al., 1999; Fromme et al., 2001; Kitanovic et al., 2001; Millar et al., 2004; Wang et al., 2004; Li et al., 2005; Oh et al., 2005). "
ABSTRACT: This minireview provides the current status on gonadotropin-releasing hormone receptors (GnRH-R) in vertebrates, from the perspective of a basal vertebrate, the sea lamprey, and provides an evolutionary scheme based on the recent advance of whole genome sequencing. In addition, we provide a perspective on the functional divergence and evolution of the receptors. In this review we use the phylogenetic classification of vertebrate GnRH receptors that groups them into three clusters: type I (mammalian and non-mammalian), type II, and type III GnRH receptors. New findings show that the sea lamprey has two type III-like GnRH receptors and an ancestral type GnRH receptor that is more closely related to the type II-like receptors. These two novel GnRH receptors along with lGnRH-R-1 share similar structural features and amino acid motifs common to other known gnathostome type II/III receptors. Recent data analyses of the lamprey genome provide strong evidence that two whole rounds of genome duplication (2R) occurred prior to the gnathostome-agnathan split. Based on our current knowledge, it is proposed that lGnRH-R-1 evolved from an ancestor of the type II receptor following a vertebrate-shared genome duplication and that the two type III receptors resulted from a duplication within lamprey of a gene derived from a lineage shared by many vertebrates.Frontiers in Endocrinology 11/2012; 3:140. DOI:10.3389/fendo.2012.00140
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- "Thus, amino acid sequence comparison of the peptide and receptor with their orthologs and paralogs, along with mutational mapping approaches, are useful tools helping to determine specific residues in the peptide ligands and receptors that are essential for maintaining selective ligand-receptor interaction. Indeed, ligand binding domains identified in mammalian receptors are highly conserved in orthologous non-mammalian receptors, indicating that there is high evolutionary selection pressure to maintain selectivity for their ligands (Acharjee et al., 2004; Wang et al., 2004; Li et al., 2005). Recently, we reported that evolutionarily conserved amino acid residues in GLP-1 and core domains of the GLP1R confer selective ligand-receptor interaction and receptor activation (Moon et al., 2010, 2012). "
ABSTRACT: Glucagon-like peptide-1 (GLP-1) is a major player in the regulation of glucose homeostasis. It acts on pancreatic beta cells to stimulate insulin secretion and on the brain to inhibit appetite. Thus, it may be a promising therapeutic agent for the treatment of type 2 diabetes mellitus and obesity. Despite the physiological and clinical importance of GLP-1, molecular interaction with the GLP-1 receptor (GLP1R) is not well understood. Particularly, the specific amino acid residues within the transmembrane helices and extracellular loops of the receptor that may confer ligand-induced receptor activation have been poorly investigated. Amino acid sequence comparisons of GLP-1 and GLP1R with their orthologs and paralogs in vertebrates, combined with biochemical approaches, are useful to determine which amino acid residues in the peptide and the receptor confer selective ligand-receptor interaction. This article reviews how the molecular evolution of GLP-1 and GLP1R contributes to the selective interaction between this ligand-receptor pair, providing critical clues for the development of potent agonists for the treatment of diabetes mellitus and obesity.Frontiers in Endocrinology 11/2012; 3:141. DOI:10.3389/fendo.2012.00141
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- "Usually , the amino acid sequences of ECL3 and its proxi - mal TMDs are highly variable among the receptors within the same family . Thus , this region is proposed to contain determinants for agonist selectivity within receptor sub - families ( Chen et al . , 2006 ; Cho et al . , 2007 ; Li et al . , 2005 ; Wang et al . , 2004 ) . Indeed , the amino acid sequence of MTR ECL3 and ECL3 - proximal TMD VII is largely different from that of VT1R , but it shows a high degree of sequence homology with OTR . Thus , agonist selectivity of MTR and VT1R is most likely attributable to some amino acids within these nonconserved regions . However , a single amino acid subs"
ABSTRACT: Mesotocin (MT) and vasotocin (VT) are the nonmammalian orthologs of mammalian oxytocin (OT) and arginine vasopressin (AVP), respectively. The OT/AVP family of peptides has arisen from gene duplication but has evolved to possess high selectivity toward their cognate receptors. The process of molecular evolution of receptors to confer high selectivity to their cognate ligands, however, is poorly understood. We constructed a series of reciprocal chimeras using a pair of bullfrog MT receptor (MTR) and VT1 receptor (VT1R) DNA fragments. Among the MTR/VT1R chimeras, the MTR chimera containing a region from transmembrane domain (TMD) VI to the carboxyl-terminal tail (C-tail) of VT1R showed an increased sensitivity to VT, while a chimeric VT1R containing TMD VI to C-tail of MTR showed an increased sensitivity to MT. Further dissection of domains using additional chimeras demonstrated that the receptor with the fragment containing extracellular loop 3 (ECL3) and ECL3-proximal TMDs VI and VII of MTR increased MT selectivity. This fragment is also important for receptor conformation that permits the signaling ability of the receptor. Particularly, the amino acids Val/Ile(6.54) in TMD VI and Pro/Glu(7.29) in ECL3 appear to be involved in this activity, since double mutation of these amino acids completely blocked signaling activity while maintaining ligand binding activity. Mutations at these residues in human OT and AVP 1a receptors markedly decreased receptor signaling activity. This study provides clues for understanding molecular coevolution of the OT/AVP peptides and their receptors with regard to receptor-ligand binding and receptor signaling activity.General and Comparative Endocrinology 04/2008; 156(1):71-82. DOI:10.1016/j.ygcen.2007.11.010 · 2.67 Impact Factor