Structure and dynamics of the active Gs-coupled human secretin receptor

Maoqing Dong,Laurence J Miller,Denise Wootten,Giuseppe Deganutti,Kaleeckal G Harikumar,Patrick M Sexton,Christopher A Reynolds,Sebastian G B Furness,Sarah J Piper,Matthew J Belousoff,Maryam Khoshouei,Arthur Christopoulos,Alisa Glukhova,Radostin Danev,Yi-Lynn Liang

doi:10.1038/s41467-020-17791-4

Abstract

The class B secretin GPCR (SecR) has broad physiological effects, with target potential for treatment of metabolic and cardiovascular disease. Molecular understanding of SecR binding and activation is important for its therapeutic exploitation. We combined cryo-electron microscopy, molecular dynamics, and biochemical cross-linking to determine a 2.3 Å structure, and interrogate dynamics, of secretin bound to the SecR:Gs complex. SecR exhibited a unique organization of its extracellular domain (ECD) relative to its 7-transmembrane (TM) core, forming more extended interactions than other family members. Numerous polar interactions formed between secretin and the receptor extracellular loops (ECLs) and TM helices. Cysteine-cross-linking, cryo-electron microscopy multivariate analysis and molecular dynamics simulations revealed that interactions between peptide and receptor were dynamic, and suggested a model for initial peptide engagement where early interactions between the far N-terminus of the peptide and SecR ECL2 likely occur following initial binding of the peptide C-terminus to the ECD.

Highlights

The class B secretin G protein-coupled receptors (GPCRs) (SecR) has broad physiological effects, with target potential for treatment of metabolic and cardiovascular disease
While there are parallels to other active class B peptide hormone receptor structures, the secretin GPCR (SecR) demonstrates a unique organization of the receptor extracellular domain (ECD) to the 7-transmembrane (TM) domain core, forming more extended interactions than other class B GPCRs
Secretin formed numerous polar interactions between the N-terminal half of the peptide and receptor extracellular loops (ECLs) and TM helices, with the importance of these interactions supported by mutagenesis data

Summary

Introduction

The class B secretin GPCR (SecR) has broad physiological effects, with target potential for treatment of metabolic and cardiovascular disease. Cysteine-cross-linking, cryo-electron microscopy multivariate analysis and molecular dynamics simulations revealed that interactions between peptide and receptor were dynamic, and suggested a model for initial peptide engagement where early interactions between the far N-terminus of the peptide and SecR ECL2 likely occur following initial binding of the peptide C-terminus to the ECD. Peptide hormone class B GPCRs are a subfamily of GPCRs that are important in physiology and disease, since their endogenous ligands play major roles in homeostatic control of bone and energy metabolism, cardiovascular, and immune responses[1] These receptors are important targets for treatment of disorders of these functions. Class B GPCRs encompass targets for approved drugs that treat diabetes, obesity, osteoporosis, hypercalcemia, and Paget’s disease, all of which are major global health burdens[1] Targeting these receptors for therapeutic benefit is suboptimal[1]. Cysteine-crosslinking analysis and MD simulations revealed that the interactions between SecR and secretin were dynamic, and suggested a model for initial peptide engagement where early interactions between the far N-terminus of the peptide and the SecR ECL2 likely occur following initial binding of the peptide C-terminus to the receptor ECD

Methods

Results

Conclusion