Structural basis for the tethered peptide activation of adhesion GPCRs

Stachel-mediated activation of adhesion G protein-coupled receptors: insights from cryo-EM studies

“…In support of the first hypothesis, mutations in the GAIN domain were identified that reduced the interactions with the tethered peptide sequence and an increase in basal activity indicated a release of the tethered peptide from the GAIN domain. 1 However, the same effect was observed in a cleavage-deficient mutant, 2 indicating that these mutations promote the activation state even without NTF removal. Support for the second hypothesis comes from a cryo-EM structure solved by Qu et al 3 Although the NTF of full-length structures is not solved most likely due to high flexibility, analysis of a cleavage-deficient full-length ADGRF1/GPR110 showed the Stachel sequence already in the 7TMD binding pocket as found in the CTF structures.…”

“…Recently, a set of cryo-electron microscopy (cryo-EM) structures of different adhesion G protein-coupled receptors (aGPCRs) has been published by Xiao et al 1 , Ping et al 2 , Qu et al 3 , and Barros-Álvarez et al 4 shedding light on the activation of the seven-helix transmembrane domain (7TMD) via their tethered peptide agonist.…”

Thwarting of Lphn3 Functions in Cell Motility and Signaling by Cancer-Related GAIN Domain Somatic Mutations

“…A cleavage motif known as the GPCR Proteolysis Site (GPS) is embedded into subdomain B before the last β-strand, generating two protomers that remain non-covalently bound to each other during their trafficking from the endoplasmic reticulum to the cell-membrane [ 15 , 16 ]. The last membrane-proximal β-strand acts as a tethered agonist by inserting itself into the GPCR region, whether cleavage at the GPS occurs or not, thus suggesting that the GAIN domain might bear crucial activation determinants [ 17 , 18 , 19 , 20 ].…”

PTK7 is a positive allosteric modulator of GPR133 (ADGRD1) signaling in GBM

“…This protein class is characterized by their long extracellular N-termini, which contain receptor-specific adhesive domains that help define the extracellular interactome (Langenhan et al , 2013; Vizurraga et al , 2020), as well as the phylogenetically conserved GPCR autoproteolysis-inducing (GAIN) domain that catalyzes intramolecular cleavage of the N-terminus at the GPCR proteolysis site (GPS) (Arac et al , 2012). In C-terminal proximity to the GPS lies an endogenous tethered agonist, the Stachel sequence, that is essential to receptor activation (Barros-Alvarez et al , 2022; Liebscher et al , 2014; Ping et al , 2022; Qu et al , 2022; Xiao et al , 2022). A popular model for aGPCR activation invokes ligand binding as a means to convey mechanical forces driving the dissociation of the cleaved extracellular N-terminal fragment (NTF) from the remaining transmembrane-spanning C-terminal fragment (CTF), which contains the Stachel sequence (Lin et al , 2022; Wilde et al , 2022).…”

“…A popular model for aGPCR activation invokes ligand binding as a means to convey mechanical forces driving the dissociation of the cleaved extracellular N-terminal fragment (NTF) from the remaining transmembrane-spanning C-terminal fragment (CTF), which contains the Stachel sequence (Lin et al , 2022; Wilde et al , 2022). This dissociation, in turn, is thought to allow the Stachel sequence to insert itself into the orthosteric binding pocket formed by the transmembrane portion of the receptor to exert agonistic effects (Barros-Alvarez et al ., 2022; Ping et al ., 2022; Qu et al ., 2022; Xiao et al ., 2022). In an alternative model inspired by the fact that cleavage-deficient mutant aGPCRs maintain signaling competency, ligand binding and mechanical forces allosterically induce conformational changes leading to receptor activation and signaling dependent on orthosteric Stachel agonism but without the requirement for NTF-CTF dissociation.…”