Structure and dynamics of the active human parathyroid hormone receptor-1

Abstract

The parathyroid hormone receptor-1 (PTH1R) is a class B G protein–coupled receptor central to calcium homeostasis and a therapeutic target for osteoporosis and hypoparathyroidism. Here we report the cryo–electron microscopy structure of human PTH1R bound to a long-acting PTH analog and the stimulatory G protein. The bound peptide adopts an extended helix with its amino terminus inserted deeply into the receptor transmembrane domain (TMD), which leads to partial unwinding of the carboxyl terminus of transmembrane helix 6 and induces a sharp kink at the middle of this helix to allow the receptor to couple with G protein. In contrast to a single TMD structure state, the extracellular domain adopts multiple conformations. These results provide insights into the structural basis and dynamics of PTH binding and receptor activation.

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

“…The recent high‐resolution structures of the PTHR1 in partially active and active‐state conformations, together with the structures obtained for several other family B GPCRs help shed light on the mechanisms by which the PTHR1 and these peptide hormone receptors as a class function. Particularly noteworthy is the finding that all known JMC mutations map to three residue positions in the PTHR1: His223, Thr410, and Ile458, which are each located at the cytosolic base of a TMD helix and at a position that strongly suggests a critical role in receptor activation.…”

“…This mechanism involves an initial docking of the (15‐34) portion of the ligand to the amino‐terminal extracellular domain (ECD) portion of the receptor and a subsequent engagement of the N‐terminal (1‐14) portion of the ligand with the extracellular loop and seven–transmembrane helical domain (TMD) region of the receptor, which leads to receptor activation . The recent high‐resolution X‐ray crystal and cryogenic electron microscopy (cryo‐EM) structures of the PTHR1, each in complex with a PTH(1‐34) or PTHrP(1‐36) analog ligand, confirm and extend this model of ligand binding. These structures thus show the peptide to be bound as a linear α‐helix with its C‐terminal portion docked to the ECD and its N‐terminal portion projecting into the core of the TMD bundle.…”

“…The residues at these positions are highly conserved in the family B GPCRs. The PTHR1 mutations of JMC can thus be predicted to perturb a critical component of the receptor located in the lower portion of the TMD bundle that controls receptor activation and deactivation …”

“…PTHR1 is a family B G-protein-coupled receptor (GPCR) and, as for each of these receptors, binds its agonist peptide ligands, such as the bioactive PTH(1-34) fragment, via a two-site mechanism. This mechanism involves an initial docking of the (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) portion of the ligand to the amino-terminal extracellular domain (ECD) portion of the receptor and a subsequent engagement of the N-terminal (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) portion of the ligand with the extracellular loop and seven-transmembrane helical domain (TMD) region of the receptor, which leads to receptor activation. (10,11) The recent high-resolution X-ray crystal (12) and cryogenic electron microscopy (cryo-EM) (13) structures of the PTHR1, each in complex with a PTH or PTHrP analog ligand, confirm and extend this model of ligand binding.…”

“…The PTHR1 mutations of JMC can thus be predicted to perturb a critical component of the receptor located in the lower portion of the TMD bundle that controls receptor activation and deactivation. (11)(12)(13)20) Inverse agonists are a subclass of antagonist ligands that can bind to an active-state receptor and revert it to an inactive conformation. (21)(22)(23) A number of competitive antagonist ligands for the PTHR1 developed from the PTH or PTHrP fragments (24)(25)(26) have been shown to function as inverse agonists in vitro and can thus suppress the basal rates of cAMP signaling in transfected COS-7 or HEK293 cells expressing a PTHR1 variant of JMC.…”