Characterization of the molecular motions of constitutively active G protein-coupled receptors for parathyroid hormone

doi:10.1016/S0301-4622(00)00222-2

Biophysical Chemistry

Volume 89, Issues 2–3, 15 February 2001, Pages 119-128

https://doi.org/10.1016/S0301-4622(00)00222-2 Get rights and content

Abstract

The molecular mechanism of constitutive activity of the G protein-coupled receptor for human parathyroid hormone (PTH1) has been examined by molecular dynamics (MD) simulations. The single point mutations H223R, T410P, and I458R, of the PTH1 receptor result in ligand-independent receptor activation. Extensive MD simulations indicate that each of the mutations, through different mechanisms, lead to very similar conformational changes of the third intracellular loop. The structural changes, centered on K405 in the C-terminus of the third intracellular loop, can be traced back to the single-point mutations by calculation of the forces and torques responsible for the collective motions of the receptor. This analysis indicates a direct correlation between the conformational preferences of the cytoplasmic loop and the mutations in different locations of the receptor: TM2 (H223R), TM6 (T410P), and TM7 (I458R). Given the pivotal role of the third intracellular loop of PTH1 in coupling to the G proteins, the structural changes induced by these single-point mutations may be responsible for the ligand-free activation of the receptor. These results coupled with the high-resolution structure of the third cytoplasmic loop of PTH1, previously determined in our laboratory, provide unique insight into the mechanism of ligand free activation of the PTH1 receptor.

Introduction

Parathyroid hormone (PTH) plays a pivotal role in the regulation of extracellular calcium homeostasis [1], [2]. PTH, along with vitamin D, is responsible for maintenance of serum calcium levels required for cellular function, adjusting for the variations from bone remodeling, renal function, and dietary intake of calcium. These physiological actions are mediated through the activation of the PTH receptor, PTH1, a member of the G protein-coupled receptor (GPCR) super family of heptahelical, transmembrane signaling proteins [3], [4].

In 1996, Jüppner and co-workers [5], [6] reported two single point mutations, H223R and T410P, in PTH1 which led to constitutively active receptors, ligand independent activity enhanced compared to basal levels. These mutations are related to Jansen's Metaphyseal Chondrodysplasia, a rare disease associated with hypercalcemia [5], [6], [7]. More recently, a third single point mutation, I458R, was observed in a patient with Jansen's disease [7], [8]. It has been shown that in mice the presence of the constitutively active receptor can overcome the effects of absence of PTH [9]. In addition to their medicinal relevance and usefulness as biochemical tools, the constitutively active receptors provide unique information into the molecular mechanism of receptor activation.

Here, we characterize the consequences of the three naturally occurring single point mutations (H223R, T410P, I458R) in the human PTH1 receptor using extensive molecular dynamics (MD) simulations. The simulations were carried out using a novel membrane mimetic which allows for extensive calculations while maintaining the overall, biphasic character of the membrane environment [10], [11]. From analysis of the simulations following established procedures [12], we correlate the single point mutations to short and long range effects on the receptor structure. Despite being dispersed through out the receptor in transmembrane helices (TM) 2, 6, and 7, (see Fig. 1), all of these substitutions lead to similar changes in the third cytoplasmic loop (IC3), centered on K405. Coupling these results with the high-resolution structure of IC3 of PTH1 [13], [14], provides insight into the molecular mechanism of ligand-independent receptor activation.

Section snippets

Model building

Modeling of the transmembrane (TM) domain of the human PTH receptor (accession number: Q03431) was carried out with the WHATIF program [15] as described previously [11], [16]. The method utilizes rhodopsin and bacteriorhodopsin [17], [18] as templates for the topological orientation and arrangement of the seven membrane-spanning helices. The receptor model was completed by addition of loops, generated using a metric matrix based DG program employing distances between adjacent TM helices as

Results

For a number of GPCRs, the extracellular N-terminus of the receptor is not required for the constitutive activity [27], [28], [29]. Our analysis of the native and mutant receptors of PTH1 is therefore focused on the relative motions of the TM helices and characterizing the effects these motions have on the intracellular domains. Utilizing procedures outlined by Weinstein and co-workers [12], the collective motions of the TM helices in the wild type and mutant receptors are compared and the

Discussion

From the first report of a constitutively active GPCR, it was recognized as a unique vehicle to probe the mechanism of receptor activation [31], [32], [33]. Many of the sites originally found to produce constitutive activity are located in the cytoplasmic portion of the receptor, especially prevalent in the third cytoplasmic loop [31], [32], [34], [35], [36], [37]. Not surprisingly IC3 has been shown to be strongly associated with coupling to the G protein [37], [38], [39], [40], [41], [42].

Acknowledgements

This work was supported, in part, by grant R29-GM54082 from the National Institutes of Health (D.F.M.) and grant 98/02903 from the Deutscher Akademischer Austauschdienst (C.R.). The authors wish to thank Dr Maria Pellegrini (Brown University) for advice and assistance.

References (58)

J.T. Potts et al.
Adv. Protein Chem.
(1982)
G. Vriend
WHAT IF
J. Mol. Graph.
(1990)
A. Bisello et al.
Parathyroid hormone–receptor interactions identified directly by photocross-linking and molecular modeling studies
J. Biol. Chem.
(1998)
R. Henderson et al.
Model for the structure of bacteriorhodopsin based on high-resolution electron cryo-microscopy
J. Mol. Biol.
(1990)
S. Hery et al.
X-Ray diffuse scattering and rigid-body motion in crystalline lysozyme probed by molecular dynamics simulation
J. Mol. Biol.
(1998)
C.A. Flanagan et al.
The functional microdomain in transmembrane helices 2 and 7 regulates expression, activation, and coupling pathways of the gonadotropin-releasing hormone receptor
J. Biol. Chem.
(1999)
T.J. Baranski et al.
C5a receptor activation. Genetic identification of critical residues in four transmembrane helices
J. Biol. Chem.
(1999)
H.H. Ho et al.
The N terminus of Kaposi's sarcoma-associated herpesvirus G protein-coupled receptor is necessary for high affinity chemokine binding but not for constitutive activity
J. Biol. Chem.
(1999)
J.A. Ballesteros et al.
The role of Pro/Hyp-kinks in determining the transmembrane helix length and gating mechanism of a [Leu]zervamicin channel
Biophys. J.
(1992)
M.A. Kjelsberg et al.
Constitutive activation of the alpha 1B-adrenergic receptor by all amino acid substitutions at a single site. Evidence for a region which constrains receptor activation
J. Biol. Chem.
(1992)

A. Lattion et al.

Constitutively active mutants of the beta1-adrenergic receptor

FEBS Lett.

(1999)

S.K. Wong et al.

Chimeric muscarinic cholinergic:beta-adrenergic receptors that are functionally promiscuous among G proteins

J. Biol. Chem.

(1994)

M.J. Tseng et al.

Influence of second and third cytoplasmic loops on binding, internalization, and coupling of chimeric bombesin/m3 muscarinic receptors

J. Biol. Chem.

(1995)

H.M. Miettinen et al.

Identification of putative sites of interaction between the human formyl peptide receptor and G protein

J. Biol. Chem.

(1999)

T. Mizobe et al.

Arrangement of transmembrane domains in adrenergic receptors. Similarity to bacteriorhodopsin

J. Biol. Chem.

(1996)

J. Liu et al.

Mutational analysis of the relative orientation of transmembrane helices I and VII in G protein-coupled receptors

J. Biol. Chem.

(1995)

A. Iida-Klein et al.

Mutations in the second cytoplasmic loop of the rat parathyroid hormone (PTH)/PTH-related protein receptor result in selective loss of PTH-stimulated phospholipase C activity

J. Biol. Chem.

(1997)

Z. Huang et al.

The N-terminal region of the third intracellular loop of the parathyroid hormone (PTH)/PTH-related peptide receptor is critical for coupling to cAMP and inositol phosphate/Ca²⁺ signal transduction pathways

J. Biol. Chem.

(1996)

B.F. O'Dowd et al.

Site-directed mutagenesis of the cytoplasmic domains of the human beta 2-adrenergic receptor. Localization of regions involved in G protein–receptor coupling

J. Biol. Chem.

(1988)

W.P. Hausdorff et al.

A mutation of the beta 2-adrenergic receptor impairs agonist activation of adenylyl cyclase without affecting high affinity agonist binding. Distinct molecular determinants of the receptor are involved in physical coupling to and functional activation of Gs

J. Biol. Chem.

(1990)

M. Rosenblatt

Parathyroid hormone: chemistry and structure-activity relations

Pathobiol. Annu.

(1981)

H. Juppner et al.

A G protein-linked receptor for parathyroid hormone and parathyroid hormone-related peptide

Science

(1991)

A.B. Abou-Samra et al.

Expression cloning of a common receptor for parathyroid hormone and parathyroid hormone-related peptide from rat osteoblast-like cells: a single receptor stimulates intracellular accumulation of both cAMP and inositol trisphosphates and increases intracellular free calcium

Proc. Natl. Acad. Sci. U.S.A.

(1992)

E. Schipani et al.

Constitutively activated receptors for parathyroid hormone and parathyroid hormone-related peptide in Jansen's metaphyseal chondrodysplasia

N. Engl. J. Med.

(1996)

E. Schipani et al.

Constitutive activation of the cyclic adenosine 3′,5′-monophosphate signaling pathway by parathyroid hormone (PTH)/PTH-related peptide receptors mutated at the two loci for Jansen's metaphyseal chondrodysplasia

Mol. Endocrinol.

(1997)

E. Schipani et al.

A novel parathyroid hormone (PTH)/PTH-related peptide receptor mutation in Jansen's metaphyseal chondrodysplasia

J. Clin. Endocrinol. Metab.

(1999)

E. Schipani et al.

Targeted expression of constitutively active receptors for parathyroid hormone and parathyroid hormone-related peptide delays endochondral bone formation and rescues mice that lack parathyroid hormone-related peptide

Proc. Natl. Acad. Sci. U.S.A.

(1997)

M. Pellegrini et al.

Binding domain of human parathyroid hormone receptor: from conformation to function

Biochemistry

(1998)

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A cannabinoid receptor 1 mutation proximal to the DRY motif results in constitutive activity and reveals intramolecular interactions involved in receptor activation
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The Insight program was then used to construct the L207A and T210I mutants from the wild-type receptor model. To mimic the cell environment, a biphasic simulation cell of water/decane/water was employed essentially as described previously (Rolz and Mierke, 2001). This places the loops and N- and C-termini in water above and below the transmembrane domains which are in a decane layer.
Activation of a G-protein-coupled receptor involves changes in specific microdomain interactions within the transmembrane region of the receptor. Here, we have focused on the role of L207, proximal to the DRY motif of the human cannabinoid receptor 1 in the interconversion of the receptor resting and active states. Ligand binding analysis of the mutant receptor L207A revealed an enhanced affinity for agonists (three- to six-fold) and a diminished affinity for inverse agonists (19- to 35-fold) compared to the wild-type receptor, properties characteristic of constitutive activity. To further examine whether this mutant adopts a ligand-independent, active form, treatment with GTPγS was used to inhibit G protein coupling. Under these conditions, the L207A receptor exhibited a 10-fold increase in affinity for the inverse agonist SR141716A, consistent with a shift away from an enhanced precoupled state. Analysis of the cellular activity of the L207A receptor showed elevated basal cyclic AMP accumulation relative to the wild type that is inhibited by SR141716A, consistent with receptor-mediated Gs precoupling. Using toxins to selectively abrogate Gs or Gi coupling, we found that CP55940 nonetheless induced only a Gi response suggesting a strong preference of this ligand-bound form for Gi in this system. Molecular dynamics simulations reveal that the single residue change of L207A impacts the association of TM3 and TM6 in the receptor by altering hydrophobic interactions involving L207, the salt bridge involving the Arg of the DRY motif, and the helical structure of TM6, consistent with events leading to activation. The structural alterations parallel those observed in models of a mutant CB₁ receptor T210I, with established constitutive activity (D'Antona, A.M., Ahn, K.H. and Kendall, D.A., 2006. Mutations of CB1 T210 produce active and inactive receptor forms: correlations with ligand affinity, receptor stability, and cellular localization. Biochemistry, 45, 5606–5617).
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Current antagonists for the parathyroid hormone (PTH)/PTH-related protein (PTHrP) receptor (PTHR) are N-terminally truncated or N-terminally modified analogs of PTH(1–34) or PTHrP(1–34) and are thought to bind predominantly to the N-terminal extracellular (N) domain of the receptor. We hypothesized that ligands that bind only to PTHR region comprised of the extracellular loops and seven transmembrane helices (the juxtamembrane or J domain) could also antagonize the PTHR. To test this, we started with the J domain-selective agonists [Gln¹⁰,Ala¹²,Har¹¹,Trp¹⁴,Arg¹⁹ (M)]PTH(1–21), [M]PTH(1–15), and [M]PTH(1–14), and introduced substitutions at positions 1–3 that were predicted to dissociate PTHR binding and cAMP signaling activities. Strong dissociation was observed with the tri-residue sequence diethylglycine (Deg)¹-para-benzoyl-l-phenylalanine (Bpa)²-Deg³. In HKRK-B7 cells, which express the cloned human PTHR, [Deg^1,3,Bpa²,M]PTH(1–21), [Deg^1,3,Bpa²,M]PTH(1–15), and [Deg^1,3,Bpa²,M]PTH(1–14) fully inhibited (IC₅₀s = 100–700 nm) the binding of ¹²⁵I-[α-aminoisobutyric acid^1,3,M]PTH(1–15) and were severely defective for stimulating cAMP accumulation. In ROS 17/2.8 cells, which express the native rat PTHR, [Deg^1,3,Bpa²,M]PTH(1–21) and [Deg^1,3,Bpa²,M]PTH(1–15) antagonized the cAMP-agonist action of PTH(1–34), as did PTHrP(5–36) (IC₅₀s = 0.7 μm, 2.6 μm, and 36 nm, respectively). In COS-7 cells expressing PTHR-delNt, which lacks the N domain of the receptor, [Deg^1,3,Bpa², M]PTH(1–21) and [Deg^1,3,Bpa²,M]PTH(1–15) inhibited the agonist actions of [α-aminoisobutyric acid^1,3]PTH(1–34) and [M]PTH(1–14) (IC₅₀s ∼1 μm), whereas PTHrP(5–36) failed to inhibit. [Deg^1,3,Bpa²,M]PTH(1–14) inhibited the constitutive cAMP-signaling activity of PTHR-tether-PTH(1–9), in which the PTH(1–9) sequence is covalently linked to the PTHR J domain, as well as that of PTHR_camH223R. Thus, the J-domain-selective N-terminal PTH fragment analogs can function as antagonists as well as inverse agonists for the PTHR. The new ligands described should be useful for further studies of the ligand binding and activation mechanisms that operate in the critical PTHR J domain.
Selective ligand-induced stabilization of active and desensitized parathyroid hormone type 1 receptor conformations
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Citation Excerpt :
The observation that regulation of signaling by PTHrP-(2–36) and Bpa1-PTHrP-(1–36) and ligand-receptor endocytosis were rescued by the mutant receptor PTH1Rc(H223R), which is defective in Gq-mediated signaling (31) but is constitutively associated with β-arrestin-2 (7), clearly indicates that the signaling selectivity of these analogs per se is not the cause of the impaired desensitization. Rather, when combined with the findings that receptor phosphorylation is not necessary for β-arrestin-2 translocation (7, 8) and with the previous characterization of the molecular motions of the PTH1Rc(H223R) mutant showing that the conformation of the third intracellular loop of the unbound receptor mutant is very similar to the one of cognate agonist-bound PTH1Rc (14), these experiments suggest that the known interaction between residue 1 of PTHrP and the extracellular end of transmembrane helix VI of PTH1Rc (16) mediates the conformational changes leading to the high affinity state for β-arrestin-2. In structural terms, interaction of Bpa1-PTHrP-(1–36) and PTHrP-(2–36) with PTH1Rc results in stabilization of a non-desensitized G protein-coupled conformation.
For many G protein-coupled receptors, agonist-induced activation is followed by desensitization, internalization, and resensitization. In most cases, these processes are dependent upon interaction of agonist-occupied receptor with cytoplasmic β-arrestins. The ligand-induced intramolecular rearrangements of the receptor responsible for the desensitized versus active conformational states, which dictate both the pharmacological properties of ligands and the biological activity of G protein-coupled receptors, have not been fully elucidated. Here, we identify specific interactions between parathyroid hormone (PTH)-related protein and the human PTH type 1 receptor (PTH1Rc) and the related receptor conformational changes that lead to β-arrestin-2-mediated desensitization. PTH-related protein analogs modified at position 1 induced selective stabilization of the active G protein-coupled state of the receptor, resulting in lack of β-arrestin-2 recruitment to the cell membrane, sustained cAMP signaling, and absence of ligand-receptor complex internalization. Mechanistically, the ligands modified at position 1, interacting with the extracellular end of helix VI of PTH1Rc, produced a translocation of transmembrane helices V and VI that differed from that induced by the cognate agonist, resulting in significantly different conformations of the third intracellular loop. These results show how specific interactions between PTH1Rc and its ligands may stabilize distinct conformational states, representing either the active G protein-coupled or a desensitized β-arrestin-coupled receptor state. In addition, they establish that sustained biological activity of PTH1Rc may be induced by appropriately designed agonist ligands.
Molecular characterization of a ligand-tethered parathyroid hormone receptor
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It was recently shown that the covalent tethering of the N-terminus of parathyroid hormone (PTH) to the seventh helical bundle of the G-protein coupled PTH-receptor (PTH1R) leads to autoactivation [Shimizu et al., J. Biol. Chem. 275 (2000) 19456–19460]. Here, we have developed molecular models for the interaction of PTH(1–11) tethered to PTH1R and refined them with molecular dynamics simulations. The starting structure of the ligand/receptor complex is based on experimental data from a series of spectroscopic structural studies of PTH(1–34) and the extracellular domains of PTH1R and intermolecular contact points derived from photoaffinity labeling. The resulting PTH1R/[Arg¹¹]PTH(1–11) complex has the N-terminus of PTH interacting with residues of the third extracellular loop of PTH1R, as a possible mode for receptor activation. The hydrophobic residues leucine-5 and methionine-8, centrally located in the N-terminal α-helix of PTH(1–11), are located in deep, well-defined hydrophobic pockets in the central core of the seventh helical bundle, consistent with the requirement of these amino acids for autoactivation. We postulate that the improved signaling properties of [Arg¹¹]PTH(1–11) over wild type PTH(1–11) is due to a stable hydrogen bond between Arg¹¹ and E444, at the beginning of TM7. The model provides atomic insight into currently available biochemical data as well as numerous putative ligand/receptor interactions, and thereby may further the rational design of reduced-size PTH agonists at the PTH1 receptor.
Identification of Determinants of Inverse Agonism in a Constitutively Active Parathyroid Hormone/Parathyroid Hormone-related Peptide Receptor by Photoaffinity Cross-linking and Mutational Analysis
2001, Journal of Biological Chemistry
Citation Excerpt :
The lack of inverse agonism exhibited by Bpa2-PTHrP-(1–36) with hP1RCAM-TP, which contains a Thr → Pro mutation at position 410 in TM6 (Fig. 1), as well as the reduced overall apparent cross-linking efficiency observed with this ligand/receptor pair, as compared with that seen with hP1RCAM-HR (28), provides evidence to suggest that the topological configuration of the heptahelical bundle of hP1RCAM-TP is different from that of hP1RCAM-HR, particularly in regard to TM6. A recent computer simulation analysis of hP1RCAM-HR and hP1RCAM-TP suggests that whereas the two mutations in these receptors produce nearly the same increased solvent accessibility of intracellular loop 3, they do so by inducing different conformational changes and motions in the TM helices (41). Recent experimental data (28, 42, 43) provide support for the notion that activate-state PTH-1 receptors can assume different conformations, and this tertiary variability may give rise to altered ligand selectivity profiles (12), such as that observed with Bpa2-PTHrP-(1–36) (28).
We have investigated receptor structural components responsible for ligand-dependent inverse agonism in a constitutively active mutant of the human parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) receptor type 1 (hP1R). This mutant receptor, hP1R-H223R (hP1R_CAM-HR), was originally identified in Jansen's chondrodysplasia and is altered in transmembrane domain (TM) 2. We utilized the PTHrP analog, [Bpa²,Ile⁵,Trp²³,Tyr³⁶]PTHrP-(1–36)-amide (Bpa²-PTHrP-(1–36)), which has valine 2 replaced byp-benzoyl-l-phenylalanine (Bpa); this substitution renders the peptide a photoreactive inverse agonist at hP1R_CAM-HR. This analog cross-linked to hP1R_CAM-HR at two contiguous receptor regions as follows: the principal cross-link site (site A) was between receptor residues Pro⁴¹⁵–Met⁴⁴¹, spanning the TM6/extracellular loop three boundary; the second cross-link site (site B) was within the TM4/TM5 region. Within the site A interval, substitution of Met⁴²⁵ to Leu converted Bpa²-PTHrP-(1–36) from an inverse agonist to a weak partial agonist; this conversion was accompanied by a relative shift of cross-linking from site A to site B. The functional effect of the M425L mutation was specific for Bpa²-containing analogs, as inverse agonism of Bpa²-PTH-(1–34) was similarly eliminated, whereas inverse agonism of [Leu¹¹,d-Trp¹²]PTHrP-(5–36) was not affected. Overall, our data indicate that interactions between residue 2 of the ligand and the extracellular end of TM6 of the hP1R play an important role in modulating the conversion between active and inactive receptor states.
The Solution Structure of the Complex Formed between α-Bungarotoxin and an 18-mer Cognate Peptide Derived from the α1 Subunit of the Nicotinic Acetylcholine Receptor from Torpedo californica
2001, Journal of Biological Chemistry
Citation Excerpt :
The 20 lowest-energy structures out of the acceptable structures for free Bgtx and for the Bgtx·α18-mer complex were selected to form an ensemble of representative final structures. The mean structure corresponding to each ensemble was calculated by a program written by Dr. Christian Rölz (40). The two mean structures (free Bgtx and Bgtx·α18-mer complex) were further partially energy-minimized using DISCOVER (Molecular Simulations, Inc.) to create representative structures complete with side chains.
The region encompassing residues 181–98 on the α1 subunit of the muscle-type nicotinic acetylcholine receptor forms a major determinant for the binding of α-neurotoxins. We have prepared an ¹⁵N-enriched 18-amino acid peptide corresponding to the sequence in this region to facilitate structural elucidation by multidimensional NMR. Our aim was to determine the structural basis for the high affinity, stoichiometric complex formed between this cognate peptide and α-bungarotoxin, a long α-neurotoxin. Resonances in the complex were assigned through heteronuclear and homonuclear NMR experiments, and the resulting interproton distance constraints were used to generate ensemble structures of the complex. Thr⁸, Pro¹⁰, Lys³⁸, Val³⁹, Val⁴⁰, and Pro⁶⁹ in α-bungarotoxin and Tyr¹⁸⁹, Tyr¹⁹⁰, Thr¹⁹¹, Cys¹⁹², Asp¹⁹⁵, and Thr¹⁹⁶ in the peptide participate in major intermolecular contacts. A comparison of the free and bound α-bungarotoxin structures reveals significant conformational rearrangements in flexible regions of α-bungarotoxin, mainly loops I, II, and the C-terminal tail. Furthermore, several of the calculated structures suggest that cation-π interactions may be involved in binding. The root mean square deviation of the polypeptide backbone in the complex is 2.07 Å. This structure provides, to date, the highest resolution description of the contacts between a prototypic α-neurotoxin and its cognate recognition sequence.

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Characterization of the molecular motions of constitutively active G protein-coupled receptors for parathyroid hormone

Abstract

Introduction

Section snippets

Model building

Results

Discussion

Acknowledgements

Adv. Protein Chem.

J. Mol. Graph.

J. Biol. Chem.

J. Mol. Biol.

J. Mol. Biol.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Biophys. J.

J. Biol. Chem.

FEBS Lett.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Parathyroid hormone: chemistry and structure-activity relations

Pathobiol. Annu.

A G protein-linked receptor for parathyroid hormone and parathyroid hormone-related peptide

Science

Expression cloning of a common receptor for parathyroid hormone and parathyroid hormone-related peptide from rat osteoblast-like cells: a single receptor stimulates intracellular accumulation of both cAMP and inositol trisphosphates and increases intracellular free calcium

Proc. Natl. Acad. Sci. U.S.A.

Constitutively activated receptors for parathyroid hormone and parathyroid hormone-related peptide in Jansen's metaphyseal chondrodysplasia

N. Engl. J. Med.

Constitutive activation of the cyclic adenosine 3′,5′-monophosphate signaling pathway by parathyroid hormone (PTH)/PTH-related peptide receptors mutated at the two loci for Jansen's metaphyseal chondrodysplasia

Mol. Endocrinol.

A novel parathyroid hormone (PTH)/PTH-related peptide receptor mutation in Jansen's metaphyseal chondrodysplasia

J. Clin. Endocrinol. Metab.

Targeted expression of constitutively active receptors for parathyroid hormone and parathyroid hormone-related peptide delays endochondral bone formation and rescues mice that lack parathyroid hormone-related peptide

Proc. Natl. Acad. Sci. U.S.A.

Binding domain of human parathyroid hormone receptor: from conformation to function

Biochemistry