Evidence for biased agonists and antagonists at the endothelin receptors.

Biased ligands represent a new strategy for the development of more effective and better tolerated drugs. To date there has been a paucity of research exploring the potential of ligands that exhibit either G protein or β-arrestin pathway selectivity at the endothelin receptors. Re-analysis of data may allow researchers to determine whether there is existing evidence that the endogenous ET peptides or currently available agonists and antagonists exhibit pathway bias in a particular physiological or disease setting and this is explored in the review. An alternative to molecules that bind at the orthosteric site of the ET receptors are cell penetrating peptides that interact with a segment of an intracellular loop of the receptor to modify signalling behaviour. One such peptide IC2B has been shown to have efficacy in a model of pulmonary arterial hypertension. Finally, understanding the molecular pathways that contribute to disease is critical to determining whether biased ligands will provide clinical benefit. The role of ETA signalling in ovarian cancer has been delineated in some detail and this has led to the suggestion that the development of ETA G protein biased agonists or β-arrestin biased antagonists should be explored.This study was supported by the Wellcome Trust (grant number WT107715). We thank Papworth Hospital NHS Trust Tissue Bank for assistance.This is the final version of the article. It first appeared from Elsevier via https://doi.org/10.1016/j.lfs.2016.02.06

Endothelin receptors and their antagonists.

All three members of the endothelin (ET) family of peptides, ET-1, ET-2, and ET-3, are expressed in the human kidney, with ET-1 being the predominant isoform. ET-1 and ET-2 bind to two G-protein-coupled receptors, ETA and ETB, whereas at physiological concentrations ET-3 has little affinity for the ET(A) receptor. The human kidney is unusual among the peripheral organs in expressing a high density of ET(B). The renal vascular endothelium only expresses the ET(B) subtype and ET-1 acts in an autocrine or paracrine manner to release vasodilators. Endothelial ETB in kidney, as well as liver and lungs, also has a critical role in scavenging ET-1 from the plasma. The third major function is ET-1 activation of ET(B) in in the nephron to reduce salt and water re-absorption. In contrast, ET(A) predominate on smooth muscle, causing vasoconstriction and mediating many of the pathophysiological actions of ET-1. The role of the two receptors has been delineated using highly selective ET(A) (BQ123, TAK-044) and ET(B) (BQ788) peptide antagonists. Nonpeptide antagonists, bosentan, macitentan, and ambrisentan, that are either mixed ET(A)/ET(B) antagonists or display ET(A) selectivity, have been approved for clinical use but to date are limited to pulmonary hypertension. Ambrisentan is in clinical trials in patients with type 2 diabetic nephropathy. This review summarizes ET-receptor antagonism in the human kidney, and considers the relative merits of selective versus nonselective antagonism in renal disease.Supported by the British Heart Foundation (PS/02/001, PG/05/127/19872, FS/12/64/130001), Wellcome Trust Programme in Metabolic and Cardiovascular Disease 096822/Z/11/Z, National Institute for Health Research Cambridge Bio-medical Research Centre, and the Pulmonary Hypertension Association United Kingdom.This is the final published version. It first appeared at http://www.seminarsinnephrology.org/article/S0270-9295%2815%2900028-5/abstract

Apelin, Elabela/Toddler, and biased agonists as novel therapeutic agents in the cardiovascular system.

Apelin and its G protein-coupled receptor (GPCR) have emerged as a key signalling pathway in the cardiovascular system. The peptide is a potent inotropic agent and vasodilator. Remarkably, a peptide, Elabela/Toddler, that has little sequence similarity to apelin, has been proposed as a second endogenous apelin receptor ligand and is encoded by a gene from a region of the genome previously classified as 'non-coding'. Apelin is downregulated in pulmonary arterial hypertension and heart failure. To replace the missing endogenous peptide, 'biased' apelin agonists have been designed that preferentially activate G protein pathways, resulting in reduced β-arrestin recruitment and receptor internalisation, with the additional benefit of attenuating detrimental β-arrestin signalling. Proof-of-concept studies support the clinical potential for apelin receptor biased agonists.We acknowledge the Wellcome Trust Programmes in Translational Medicine and Therapeutics (085686) and in Metabolic and Cardiovascular Disease (096822/Z/11/Z), the British Heart Foundation PG/09/050/27734, MRC and the NIHR Cambridge Biomedical Research Centre.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.tips.2015.06.00

Kisspeptin receptor (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The kisspeptin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on the kisspeptin receptor [9]), like neuropeptide FF (NPFF), prolactin-releasing peptide (PrP) and QRFP receptors (provisional nomenclature) responds to endogenous peptides with an arginine-phenylalanine-amide (RFamide) motif. kisspeptin-54 (KP54, originally named metastin), kisspeptin-13 (KP13) and kisspeptin-10 (KP10) are biologically-active peptides cleaved from the KISS1 (Q15726) gene product. Kisspeptins have roles in, for example, cancer metastasis, fertility/puberty regulation and glucose homeostasis

Neuropeptide W/neuropeptide B receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The neuropeptide BW receptor 1 (NPBW1, provisional nomenclature [5]) is activated by two 23-amino-acid peptides, neuropeptide W (neuropeptide W-23) and neuropeptide B (neuropeptide B-23) [20, 6]. C-terminally extended forms of the peptides (neuropeptide W-30 and neuropeptide B-29) also activate NPBW1 [2]. Unique to both forms of neuropeptide B is the N-terminal bromination of the first tryptophan residue, and it is from this post-translational modification that the nomenclature NPB is derived. These peptides were first identified from bovine hypothalamus and therefore are classed as neuropeptides. Endogenous variants of the peptides without the N-terminal bromination, des-Br-neuropeptide B-23 and des-Br-neuropeptide B-29, were not found to be major components of bovine hypothalamic tissue extracts. The NPBW2 receptor is activated by the short and C-terminal extended forms of neuropeptide W and neuropeptide B [2]

Neuropeptide W/neuropeptide B receptors in GtoPdb v.2023.1

The neuropeptide BW receptor 1 (NPBW1, provisional nomenclature [6]) is activated by two 23-amino-acid peptides, neuropeptide W (neuropeptide W-23) and neuropeptide B (neuropeptide B-23) [22, 7]. C-terminally extended forms of the peptides (neuropeptide W-30 and neuropeptide B-29) also activate NPBW1 [2]. Unique to both forms of neuropeptide B is the N-terminal bromination of the first tryptophan residue, and it is from this post-translational modification that the nomenclature NPB is derived. These peptides were first identified from bovine hypothalamus and therefore are classed as neuropeptides. Endogenous variants of the peptides without the N-terminal bromination, des-Br-neuropeptide B-23 and des-Br-neuropeptide B-29, were not found to be major components of bovine hypothalamic tissue extracts. The NPBW2 receptor is activated by the short and C-terminal extended forms of neuropeptide W and neuropeptide B [2]

Kisspeptin receptor (version 2020.4) in the IUPHAR/BPS Guide to Pharmacology Database

The kisspeptin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on the kisspeptin receptor [9]), like neuropeptide FF (NPFF), prolactin-releasing peptide (PrP) and QRFP receptors (provisional nomenclature) responds to endogenous peptides with an arginine-phenylalanine-amide (RFamide) motif. kisspeptin-54 (KP54, originally named metastin), kisspeptin-13 (KP13) and kisspeptin-10 (KP10) are biologically-active peptides cleaved from the KISS1 (Q15726) gene product. Kisspeptins have roles in, for example, cancer metastasis, fertility/puberty regulation and glucose homeostasis

Kisspeptin receptor in GtoPdb v.2023.1

The kisspeptin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on the kisspeptin receptor [11]), like neuropeptide FF (NPFF), prolactin-releasing peptide (PrP) and QRFP receptors (provisional nomenclature) responds to endogenous peptides with an arginine-phenylalanine-amide (RFamide) motif. kisspeptin-54 (KP54, originally named metastin), kisspeptin-13 (KP13) and kisspeptin-10 (KP10) are biologically-active peptides cleaved from the KISS1 (Q15726) gene product. Kisspeptins have roles in, for example, cancer metastasis, fertility/puberty regulation and glucose homeostasis

Ghrelin receptor (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The ghrelin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee for the Ghrelin receptor [18]) is activated by a 28 amino-acid peptide originally isolated from rat stomach, where it is cleaved from a 117 amino-acid precursor (GHRL, Q9UBU3). The human gene encoding the precursor peptide has 83% sequence homology to rat prepro-ghrelin, although the mature peptides from rat and human differ by only two amino acids [70]. Alternative splicing results in the formation of a second peptide, [des-Gln14]ghrelin with equipotent biological activity [48]. A unique post-translational modification (octanoylation of Ser3, catalysed by ghrelin Ο-acyltransferase (MBOAT4, Q96T53) [127] occurs in both peptides, essential for full activity in binding to ghrelin receptors in the hypothalamus and pituitary, and for the release of growth hormone from the pituitary [56]. Structure activity studies showed the first five N-terminal amino acids to be the minimum required for binding [4], and receptor mutagenesis has indicated overlap of the ghrelin binding site with those for small molecule agonists and allosteric modulators of ghrelin function [43]. In cell systems, the ghrelin receptor is constitutively active [44], but this is abolished by a naturally occurring mutation (A204E) that results in decreased cell surface receptor expression and is associated with familial short stature [88]

Apelin receptor in GtoPdb v.2023.1

The apelin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on the apelin receptor [73] and subsequently updated [75]) responds to apelin, a 36 amino-acid peptide derived initially from bovine stomach. apelin-36, apelin-13 and [Pyr1]apelin-13 are the predominant endogenous ligands which are cleaved from a 77 amino-acid precursor peptide (APLN, Q9ULZ1) [88]. A second family of peptides discovered independently and named Elabela [13] or Toddler, that has little sequence similarity to apelin, is present, and functional at the apelin receptor in the adult cardiovascular system [97, 71]. The enzymatic pathways generating biologically active apelin and Elabela isoforms have not been determined but both propeptides include sites for potential proprotein convertase processing [81]. Structure-activity relationship Elabela analogues have been described [65, 90]. The stoichiometry of apelin receptor-heterotrimeric G protein complexes has been studied using cryogenic-electron microscopy [98]