Rearrangement of a polar core provides a conserved mechanism for constitutive activation of class B G protein-coupled receptors

Yanting Yin; Parker W de Waal; Yuanzheng He; Li-Hua Zhao; Dehua Yang; Xiaoqing Cai; Yi Jiang; Karsten Melcher; Ming-Wei Wang; H Eric Xu

doi:10.1074/jbc.M117.782987

Rearrangement of a polar core provides a conserved mechanism for constitutive activation of class B G protein-coupled receptors

J Biol Chem. 2017 Jun 16;292(24):9865-9881. doi: 10.1074/jbc.M117.782987. Epub 2017 Mar 29.

Authors

Yanting Yin^{1

2

3}, Parker W de Waal², Yuanzheng He², Li-Hua Zhao¹, Dehua Yang⁴, Xiaoqing Cai⁴, Yi Jiang¹, Karsten Melcher², Ming-Wei Wang^{5

6}, H Eric Xu^{7

2

3}

Affiliations

¹ From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China.
² the Laboratory of Structural Sciences and Laboratory of Structural Biology and Biochemistry, Van Andel Research Institute, Grand Rapids, Michigan 49503.
³ the University of Chinese Academy of Sciences, Number 19A Yuquan Road, Beijing 100049, China.
⁴ The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China, and.
⁵ The National Center for Drug Screening and the CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China, and [email protected].
⁶ the School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China.
⁷ From the Van Andel Research Institute - Shanghai Institute of Materia Medica (VARI-SIMM) Center, Center for Structure and Function of Drug Targets, The CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences (CAS), Shanghai 201203, China, [email protected].

Abstract

The glucagon receptor (GCGR) belongs to the secretin-like (class B) family of G protein-coupled receptors (GPCRs) and is activated by the peptide hormone glucagon. The structures of an activated class B GPCR have remained unsolved, preventing a mechanistic understanding of how these receptors are activated. Using a combination of structural modeling and mutagenesis studies, we present here two modes of ligand-independent activation of GCGR. First, we identified a GCGR-specific hydrophobic lock comprising Met-338 and Phe-345 within the IC3 loop and transmembrane helix 6 (TM6) and found that this lock stabilizes the TM6 helix in the inactive conformation. Disruption of this hydrophobic lock led to constitutive G protein and arrestin signaling. Second, we discovered a polar core comprising conserved residues in TM2, TM3, TM6, and TM7, and mutations that disrupt this polar core led to constitutive GCGR activity. On the basis of these results, we propose a mechanistic model of GCGR activation in which TM6 is held in an inactive conformation by the conserved polar core and the hydrophobic lock. Mutations that disrupt these inhibitory elements allow TM6 to swing outward to adopt an active TM6 conformation similar to that of the canonical β₂-adrenergic receptor complexed with G protein and to that of rhodopsin complexed with arrestin. Importantly, mutations in the corresponding polar core of several other members of class B GPCRs, including PTH1R, PAC1R, VIP1R, and CRFR1, also induce constitutive G protein signaling, suggesting that the rearrangement of the polar core is a conserved mechanism for class B GPCR activation.

Keywords: 7-helix receptor; G protein-coupled receptor (GPCR); arrestin; glucagon; parathyroid hormone.

MeSH terms

Amino Acid Sequence
Amino Acid Substitution
Binding Sites
CRF Receptor, Type 1
Cell Line
Conserved Sequence
Humans
Hydrophobic and Hydrophilic Interactions
Ligands
Models, Molecular*
Mutagenesis, Site-Directed
Mutation
Peptide Fragments / agonists
Peptide Fragments / chemistry
Peptide Fragments / genetics
Peptide Fragments / metabolism
Protein Conformation
Protein Interaction Domains and Motifs
Protein Stability
Receptor, Parathyroid Hormone, Type 1 / agonists*
Receptor, Parathyroid Hormone, Type 1 / chemistry
Receptor, Parathyroid Hormone, Type 1 / genetics
Receptor, Parathyroid Hormone, Type 1 / metabolism
Receptors, Corticotropin-Releasing Hormone / agonists*
Receptors, Corticotropin-Releasing Hormone / chemistry
Receptors, Corticotropin-Releasing Hormone / genetics
Receptors, Corticotropin-Releasing Hormone / metabolism
Receptors, Glucagon / agonists*
Receptors, Glucagon / chemistry
Receptors, Glucagon / genetics
Receptors, Glucagon / metabolism
Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / agonists*
Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / chemistry
Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / genetics
Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I / metabolism
Receptors, Vasoactive Intestinal Polypeptide, Type I / agonists*
Receptors, Vasoactive Intestinal Polypeptide, Type I / chemistry
Receptors, Vasoactive Intestinal Polypeptide, Type I / genetics
Receptors, Vasoactive Intestinal Polypeptide, Type I / metabolism
Recombinant Fusion Proteins / chemistry
Recombinant Fusion Proteins / metabolism
Recombinant Proteins / chemistry
Recombinant Proteins / metabolism
Second Messenger Systems
Structural Homology, Protein

Substances

ADCYAP1R1 protein, human
Ligands
PTH1R protein, human
Peptide Fragments
Receptor, Parathyroid Hormone, Type 1
Receptors, Corticotropin-Releasing Hormone
Receptors, Glucagon
Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
Receptors, Vasoactive Intestinal Polypeptide, Type I
Recombinant Fusion Proteins
Recombinant Proteins
VIPR1 protein, human
CRF Receptor, Type 1

Associated data

PDB/5EE7
PDB/3SN6
PDB/4ZWJ

Abstract

MeSH terms

Substances

Associated data

Grants and funding