title: Inhibitory mechanism of an allosteric antibody targeting the glucagon receptor.
abstract: Elevated glucagon levels and increased hepatic glucagon receptor (GCGR) signaling contribute to hyperglycemia in type 2 diabetes. We have identified a monoclonal antibody that inhibits GCGR, a class B G-protein coupled receptor (GPCR), through a unique allosteric mechanism. Receptor inhibition is mediated by the binding of this antibody to two distinct sites that lie outside of the glucagon binding cleft. One site consists of a patch of residues that are surface-exposed on the face of the extracellular domain (ECD) opposite the ligand-binding cleft, whereas the second binding site consists of residues in the αA helix of the ECD. A docking model suggests that the antibody does not occlude the ligand-binding cleft. We solved the crystal structure of GCGR ECD containing a naturally occurring G40S mutation and found a shift in the register of the αA helix that prevents antibody binding. We also found that alterations in the αA helix impact the normal function of GCGR. We present a model for the allosteric inhibition of GCGR by a monoclonal antibody that may form the basis for the development of allosteric modulators for the treatment of diabetes and other class B GPCR-related diseases.
authors.affiliation: From the Departments of Structural Biology.
authors.forename: Susmith
authors.initials: S
authors.lastname: Mukund
authors.forename: Yonglei
authors.initials: Y
authors.lastname: Shang
authors.forename: Holly J
authors.initials: HJ
authors.lastname: Clarke
authors.forename: Azadeh
authors.initials: A
authors.lastname: Madjidi
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Corn
authors.forename: Lance
authors.initials: L
authors.lastname: Kates
authors.forename: Ganesh
authors.initials: G
authors.lastname: Kolumam
authors.forename: Vicky
authors.initials: V
authors.lastname: Chiang
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Luis
authors.forename: Jeremy
authors.initials: J
authors.lastname: Murray
authors.forename: Yingnan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Isidro
authors.initials: I
authors.lastname: Hötzel
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Koth
authors.forename: Bernard B
authors.initials: BB
authors.lastname: Allan
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D018360:Crystallography, X-Ray; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D018027:Receptors, Glucagon / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D018027:Receptors, Glucagon
keywords: Antibody Engineering; Diabetes; G Protein-coupled Receptors (GPCR); Glucose Metabolism; Structural Biology