Structural basis for activation of the growth hormone-releasing hormone receptor

Abstract

Growth hormone-releasing hormone (GHRH) regulates the secretion of growth hormone that virtually controls metabolism and growth of every tissue through its binding to the cognate receptor (GHRHR). Malfunction in GHRHR signaling is associated with abnormal growth, making GHRHR an attractive therapeutic target against dwarfism (e.g., isolated growth hormone deficiency, IGHD), gigantism, lipodystrophy and certain cancers. Here, we report the cryo-electron microscopy (cryo-EM) structure of the human GHRHR bound to its endogenous ligand and the stimulatory G protein at 2.6 Å. This high-resolution structure reveals a characteristic hormone recognition pattern of GHRH by GHRHR, where the α-helical GHRH forms an extensive and continuous network of interactions involving all the extracellular loops (ECLs), all the transmembrane (TM) helices except TM4, and the extracellular domain (ECD) of GHRHR, especially the N-terminus of GHRH that engages a broad set of specific interactions with the receptor. Mutagenesis and molecular dynamics (MD) simulations uncover detailed mechanisms by which IGHD-causing mutations lead to the impairment of GHRHR function. Our findings provide insights into the molecular basis of peptide recognition and receptor activation, thereby facilitating the development of structure-based drug discovery and precision medicine.

Evolving cryo-EM structural approaches for GPCR drug discovery

“…Our application of 3D variance analysis to recently solved structures of class B GPCRs, including adenomedullin-1 (AM1) and AM2 receptors 19 , the secretin receptor 20 and GLP-1R bound to peptide and small molecule agonists 14 has revealed common rocking and rotational motions of the G protein relative to the receptors. This is consistent with transient formation and breakage of interactions that are likely to be important in receptor-mediated G protein recruitment and activation, and low resolution for parts of ICL3 and the extension of H8 for class B GPCRs 3,8,9,15,[19][20][21][22][23][24][25][26][27][28] are consistent with transient interactions between these domains and the G protein. ICL2 exhibited densities consistent with 2 metastable conformations that exhibited differences in the consensus maps solved in the presence and absence of Nb35, and where higher resolution was apparent for the complex without Nb35.…”

“…A key conformational change required nucleotide exchange is outward movement of the AHD of Gs, relative to the ras-like domain. The AHD of Gαs in the nucleotide-free state is highly mobile, thereby occupying different positions around the ras-like domain 30 , and it is poorly resolved in most consensus cryo-EM maps of solved class B GPCR-G protein complexes 3,8,9,15,[19][20][21][22][23][24][25][26][27][28] . When bound with Nb35, 3D multivariate analysis of PF 06882961-GLP-1R-DNGs complex revealed translational motion between open ("up" position) and more closed ("down" position) conformations of the AHD.…”

A unique hormonal recognition feature of the human glucagon-like peptide-2 receptor

“…The overall structure of active GLP-2R–G s complex is similar to other class B GPCR–G s complexes such as GLP-1–GLP-1R–G s , 13 ExP5–GLP-1R–G s , 17 glucagon–GCGR–G s , 18 LA-PTH–PTH1R–G s 19 and GHRH–GHRHR–G s , 26 with root mean square deviation (RMSD) values of 1.76, 1.05, 1.55, 1.09 and 0.95 Å for the whole complex, respectively. When pointing toward the glucagon receptor subfamily, notable conformational differences were observed in the extracellular half of GLP-2R where the peptide hormone binds, especially in TM1, ECL1 and TM7, indicating that GLP-2R utilizes a distinct peptide-recognition mode specific for GLP-2, but not for GLP-1, glucagon or GHRH.…”

Cryo-EM structure of the human histamine H1 receptor/Gq complex

“…2 ). This strategy has been successfully used in solving several GPCR/G-protein complexes structures, including the vasoactive intestinal polypeptide receptor 21 (VIP1R)/G s and growth hormone-releasing hormone receptor/G s complexes 22 . Indeed, the NanoBiT tethering strategy greatly improves the composition of the complex (Supplementary Fig.…”