Biology subjects

Piper, S. J.

Publications and source records attributed to Piper, S. J..

3 recordsLinked to original sources

bioRxiv2022

Molecular insights into peptide agonist engagement with the PTH1 receptor

The parathyroid hormone (PTH) 1 receptor (PTH1R) is a class B1 G protein-coupled receptor (GPCR) that critically regulates skeletal development and calcium homeostasis. Despite extensive study, the molecular underpinnings of PTH1R stimulation by its cognate hormones, as well as by therapeutic agents, remain unclear. Here, we describe cryo-EM structures of the PTH1R in complex with active fragments of the two hormones, PTH and parathyroid hormone related protein (PTHrP), the peptidic drug abaloparatide, as well as the engineered tool compounds, long-acting PTH (LA-PTH) and the truncated peptide, M-PTH(1-14). We found that the N-terminus of each agonist that is critical for activity, engages the transmembrane bundle in a topologically similar fashion, which reflects similarities in measures of Gs activation. The full-length peptides bind the extracellular domain (ECD) using a shared interface but induce subtly different ECD orientations relative to the transmembrane domain (TMD). In the structure bound to M-PTH, an agonist which only binds the TMD, the ECD is completely unresolved, demonstrating that the ECD is highly dynamic when unconstrained by a peptide. High resolutions enabled identification of water molecules near the peptide and G protein binding sites, some of which are structurally conserved with other class B1 GPCRs. Our results shed light on the action of orthosteric agonists of the PTH1R and provide a foundation for structure based-drug design.

biochemistry↗

bioRxiv2021

Structures of the human cholecystokinin 1 (CCK1) receptor bound to Gs and Gq mimetic proteins: insight into mechanisms of G protein selectivity

G protein-coupled receptors (GPCRs) are critical regulators of cellular function acting via heterotrimeric G proteins as their primary transducers with individual GPCRs capable of pleiotropic coupling to multiple G proteins. Structural features governing G protein selectivity and promiscuity are currently unclear. Here we used cryo-electron microscopy to determine structures of the CCK1R bound to the CCK peptide agonist, CCK-8 and two distinct transducer proteins, its primary transducer Gq, and the more weakly coupled Gs. As seen with other Gq/11-GPCR complexes, the Gq-5 helix bound to a relatively narrow pocket in the CCK1R core. Surprisingly, the backbone of the CCK1R and volume of the G protein binding pocket was essentially equivalent when Gs was bound, with the Gs 5 helix displaying a conformation that arises from "unwinding" of the far C-terminal residues, compared to canonically Gs coupled receptors. Thus, integrated changes in the conformations of both the receptor and G protein play critical roles in the promiscuous coupling of individual GPCRs. One-Sentence SummaryCryo-EM structures of the CCK-1R reveal key mechanisms for promiscuous G protein coupling.

pharmacology and toxicology↗

bioRxiv2021

Structural and Functional Diversity among Agonist-Bound States of the GLP-1 Receptor

Recent advances in G protein-coupled receptor (GPCR) structural elucidation have strengthened previous hypotheses that multi-dimensional signal propagation mediated by these receptors is, in part, dependent on their conformational mobility. However, the relationship between receptor function and static structures determined via crystallography or cryo-electron microscopy is not always clear. This study examines the contribution of peptide agonist conformational plasticity to activation of the glucagon-like peptide-1 receptor (GLP-1R), an important clinical target. We employ variants of the peptides GLP-1 and exendin-4 to explore the interplay between helical propensity near the agonist N-terminus and the ability to bind to and activate the receptor. Cryo-EM analysis of a complex involving an exendin-4 analogue, the GLP-1R and Gs protein revealed two receptor conformers with distinct modes of peptide-receptor engagement. Our functional and structural data suggest that receptor conformational dynamics associated with flexibility of the peptide N-terminal activation domain may be a key determinant of agonist efficacy.

pharmacology and toxicology↗