Role of Amino Acid Side Chains in Region 17–31 of Parathyroid Hormone (PTH) in Binding to the PTH Receptor

The principal receptor-binding domain (Ser(17)-Val(31)) of parathyroid hormone (PTH) is predicted to form an amphiphilic alpha-helix and to interact primarily with the N-terminal extracellular domain (N domain) of the PTH receptor (PTHR). We explored these hypotheses by introducing a variety of substitutions in region 17-31 of PTH-(1-31) and assessing, via competition assays, their effects on binding to the wild-type PTHR and to PTHR-delNt, which lacks most of the N domain. Substitutions at Arg(20) reduced affinity for the intact PTHR by 200-fold or more, but altered affinity for PTHR-delNt by 4-fold or less. Similar effects were observed for Glu substitutions at Trp(23), Leu(24), and Leu(28), which together form the hydrophobic face of the predicted amphiphilic alpha-helix. Glu substitutions at Arg(25), Lys(26), and Lys(27) (which forms the hydrophilic face of the helix) caused 4-10-fold reductions in affinity for both receptors. Thus, the side chains of Arg(20), together with those composing the hydrophobic face of the ligand's putative amphiphilic alpha-helix, contribute strongly to PTHR-binding affinity by interacting specifically with the N domain of the receptor. The side chains projecting from the opposite helical face contribute weakly to binding affinity by different mechanisms, possibly involving interactions with the extracellular loop/transmembrane domain region of the receptor. The data help define the roles that side chains in the binding domain of PTH play in the PTH-PTHR interaction process and provide new clues for understanding the overall topology of the bimolecular complex

Catalog of selected heavy duty transport energy management models

A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle

Backbone modification of a polypeptide drug alters duration of action in vivo

because of protease-catalyzed degradation. We used PTHR1 signaling to evaluate a strategy for creating active and biostable backbone-modified analogs of the well-known agonist PTH(1-34). PTH is an 84-residue protein that controls key physiological processes, including the maintenance of extracellular levels of calcium and phosphate and bone homeostasis 1 . PTH(1-34) matches full-length PTH in potency and efficacy at PTHR1 and is the active ingredient in the osteoporosis drug teriparatide (Forteo). As with many other peptide-based therapeutics, PTH(1-34) has a short half-life in the bloodstream (<30 min) 2 . Therapeutic effects for osteoporosis treatment appear to be maximized by pulsatile rather than continuous exposure to PTH(1-34), but the optimal exposure cycle is unclear 3 . We generated new analogs of PTH(1-34) by replacing selected α-amino acid residues with homologous β-amino acid residues, an unconventional approach that alters the backbone but can maintain the natural side chain complement. The results show that this technically straightforward strategy can provide hormone analogs that display native-like receptor activation potencies and prolonged residency in the bloodstream. The C-terminal portion of PTH(1-34) forms an α-helix upon binding to the receptor, but the bioactive conformation of the N-terminal segment is unknown. The backbone-modification strategy described here is based on previous studies showing that α-helical segments Systematic modification of the backbone of bioactive polypeptides through b-amino acid residue incorporation could provide a strategy for generating molecules with improved drug properties, but such alterations can result in lower receptor affinity and potency. Using an agonist of parathyroid hormone receptor-1 (PTHR1), a G protein-coupled receptor in the B-family, we present an approach for a→b residue replacement that enables both high activity and improved pharmacokinetic properties in vivo. involved in protein-recognition processes can be mimicked by oligomers containing mixtures of α and β residues 4,5 . Other types of unnatural oligomers, such as peptides composed of D-α-amino acid residues 6 , peptoids 7 and β-peptides 8 , have been explored for functional mimicry of bioactive α-helices; however, none of these alternative molecular scaffolds allows faithful mimicry of a long α-helix 5 , as required for potent analogs of PTH. In previous studies, PTH analogs containing one to three β-residue replacements were used to probe local conformational requirements, and many of these replacements caused profound declines in agonist activity We prepared all four PTH(1-34) analogs containing five α→β 3 replacements in an αααβ pattern 13 within the C-terminal region (A5-D5 in PTHR1 has two distinct functional states: RG, which forms when the intracellular portion contacts G αS (a heterotrimeric G-protein responsible for activating adenylate cyclase upon receptor activation); and R 0 , which forms independent of G αS 15,16 . An agonist's affinity for the RG state correlates with PTHR1 activation potency, whereas R 0 affinity correlates with the duration of some in vivo response

An Inverse Agonist Ligand of the PTH Receptor Partially Rescues Skeletal Defects in a Mouse Model of Jansen’s Metaphyseal Chondrodysplasia

Jansen’s metaphyseal chondrodysplasia (JMC) is a rare disease of bone and mineral ion physiology that is caused by activating mutations in PTHR1. Ligand‐independent signaling by the mutant receptors in cells of bone and kidney results in abnormal skeletal growth, excessive bone turnover, and chronic hypercalcemia and hyperphosphaturia. Clinical features further include short stature, limb deformities, nephrocalcinosis, and progressive losses in kidney function. There is no effective treatment option available for JMC. In previous cell‐based assays, we found that certain N‐terminally truncated PTH and PTHrP antagonist peptides function as inverse agonists and thus can reduce the high rates of basal cAMP signaling exhibited by the mutant PTHR1s of JMC in vitro. Here we explored whether one such inverse agonist ligand, [Leu11,dTrp12,Trp23,Tyr36]‐PTHrP(7‐36)NH2 (IA), can be effective in vivo and thus ameliorate the skeletal abnormalities that occur in transgenic mice expressing the PTHR1‐H223R allele of JMC in osteoblastic cells via the collagen‐1α1 promoter (C1HR mice). We observed that after 2 weeks of twice‐daily injection and relative to vehicle controls, the IA analog resulted in significant improvements in key skeletal parameters that characterize the C1HR mice, because it reduced the excess trabecular bone mass, bone marrow fibrosis, and levels of bone turnover markers in blood and urine. The overall findings provide proof‐of‐concept support for the notion that inverse agonist ligands targeted to the mutant PTHR1 variants of JMC can have efficacy in vivo. Further studies of such PTHR1 ligand analogs could help open paths toward the first treatment option for this debilitating skeletal disorder. © 2019 American Society for Bone and Mineral Research.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154322/1/jbmr3913-sup-0001-Supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154322/2/jbmr3913.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154322/3/jbmr3913_am.pd

Parathyroid hormone receptors in GtoPdb v.2021.3

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [49]) are class B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors. The structure of a long-active PTH analogue (LA-PTH, an hybrid of PTH-(1-13) and PTHrP-(14-36)) bound to the PTH1 receptor-Gs complex has been resolved by cryo-electron microscopy [147]. Another structure of a PTH-(1-34) analog bound to a thermostabilized inactive PTH1 receptor has been obtained with X-ray crytallography [34]

Parathyroid hormone receptors in GtoPdb v.2023.1

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [50]) are class B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors. The structure of a long-active PTH analogue (LA-PTH, an hybrid of PTH-(1-13) and PTHrP-(14-36)) bound to the PTH1 receptor-Gs complex has been resolved by cryo-electron microscopy [148]. Another structure of a PTH-(1-34) analog bound to a thermostabilized inactive PTH1 receptor has been obtained with X-ray crytallography [35]

Parathyroid hormone receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

The parathyroid hormone receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Parathyroid Hormone Receptors [47]) are family B G protein-coupled receptors. The parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor (PTH1 receptor) is activated by precursor-derived peptides: PTH (84 amino acids), and PTHrP (141 amino-acids) and related peptides (PTH-(1-34), PTHrP-(1-36)). The parathyroid hormone 2 receptor (PTH2 receptor) is activated by the precursor-derived peptide TIP39 (39 amino acids). [125I]PTH may be used to label both PTH1 and PTH2 receptors

PURA-Related Developmental and Epileptic Encephalopathy Phenotypic and Genotypic Spectrum

Background and Objectives Purine-rich element-binding protein A (PURA) gene encodes Pur-α, a conserved protein essential for normal postnatal brain development. Recently, a PURA syndrome characterized by intellectual disability, hypotonia, epilepsy, and dysmorphic features was suggested. The aim of this study was to define and expand the phenotypic spectrum of PURA syndrome by collecting data, including EEG, from a large cohort of affected patients. Methods Data on unpublished and published cases were collected through the PURA Syndrome Foundation and the literature. Data on clinical, genetic, neuroimaging, and neurophysiologic features were obtained. Results A cohort of 142 patients was included. Characteristics of the PURA syndrome included neonatal hypotonia, feeding difficulties, and respiratory distress. Sixty percent of the patients developed epilepsy with myoclonic, generalized tonic-clonic, focal seizures, and/or epileptic spasms. EEG showed generalized, multifocal, or focal epileptic abnormalities. Lennox-Gastaut was the most common epilepsy syndrome. Drug refractoriness was common: 33.3% achieved seizure freedom. We found 97 pathogenic variants in PURA without any clear genotype-phenotype associations. Discussion The PURA syndrome presents with a developmental and epileptic encephalopathy with characteristics recognizable from neonatal age, which should prompt genetic screening. Sixty percent have drug-resistant epilepsy with focal or generalized seizures. We collected more than 90 pathogenic variants without observing overt genotype-phenotype associations

New Copy Number Variations in Schizophrenia

Genome-wide screenings for copy number variations (CNVs) in patients with schizophrenia have demonstrated the presence of several CNVs that increase the risk of developing the disease and a growing number of large rare CNVs; the contribution of these rare CNVs to schizophrenia remains unknown. Using Affymetrix 6.0 arrays, we undertook a systematic search for CNVs in 172 patients with schizophrenia and 160 healthy controls, all of Italian origin, with the aim of confirming previously identified loci and identifying novel schizophrenia susceptibility genes. We found five patients with a CNV occurring in one of the regions most convincingly implicated as risk factors for schizophrenia: NRXN1 and the 16p13.1 regions were found to be deleted in single patients and 15q11.2 in 2 patients, whereas the 15q13.3 region was duplicated in one patient. Furthermore, we found three distinct patients with CNVs in 2q12.2, 3q29 and 17p12 loci, respectively. These loci were previously reported to be deleted or duplicated in patients with schizophrenia but were never formally associated with the disease. We found 5 large CNVs (>900 kb) in 4q32, 5q14.3, 8q23.3, 11q25 and 17q12 in five different patients that could include some new candidate schizophrenia susceptibility genes. In conclusion, the identification of previously reported CNVs and of new, rare, large CNVs further supports a model of schizophrenia that includes the effect of multiple, rare, highly penetrant variants

A new multi-system disorder caused by the Gαs mutation p.F376V

Context The alpha-subunit of the stimulatory G-protein (Gαs) links numerous receptors to adenylyl cyclase. Gαs, encoded by GNAS, is expressed predominantly from the maternal allele in certain tissues. Thus, maternal heterozygous loss-of-function mutations cause hormonal resistance, as in pseudohypoparathyroidism type Ia, while somatic gain-of-function mutations cause hormone-independent endocrine stimulation, as in McCune-Albright Syndrome. Objective We here report two unrelated boys presenting with a new combination of clinical findings that suggest both gain and loss of Gαs function. Design, Setting Clinical features were studied and sequencing of GNAS was performed. Signaling capacities of wild-type and mutant-Gαs were determined in the presence of different G protein-coupled receptors (GPCRs) under basal and agonist-stimulated conditions. Results Both unrelated patients presented with unexplained hyponatremia in infancy, followed by severe early-onset gonadotrophin-independent precocious puberty and skeletal abnormalities. An identical heterozygous de novo variant (c.1136T>G; p.F376V) was found on the maternal GNAS allele, in both patients; this resulted in a clinical phenotype that differ from known Gαs-related diseases and suggested gain-of-function at the receptors for vasopressin (V2R) and lutropin (LHCGR), yet increased serum parathyroid hormone (PTH) concentrations indicative of impaired proximal tubular PTH1 receptor (PTH1R) function. In vitro studies demonstrated that Gαs-F376V enhanced ligand-independent signaling at the PTH1R, LHCGR and V2R and, at the same time, blunted ligand-dependent responses. Structural homology modeling suggested mutation-induced modifications at the C-terminal α5-helix of Gαs that are relevant for interaction with GPCRs and signal transduction. Conclusions The Gαs p.F376V mutation causes a previously unrecognized multi-system disorder