Extended Data Fig. 1: Structure–function relationships of aGPCRs and functionality of the NRS technique.

a, aGPCRs are composed of extra- (ECR) and intracellular regions (ICR) as well as a heptahelical transmembrane-spanning domain (7TM). Owing to autocatalytic cleavage by the GPCR autoproteolysis-inducing (GAIN) domain, most aGPCRs exist as non-covalently stabilized heterodimers composed of an N- (NTF) and C-terminal fragment (CTF), which are affixed to each other by the GAIN domain that contains the tethered agonist (TA)/Stachel. The latrophilin-like Cirl receptor contains rhamnose-binding lectin (RBL) and hormone-receptor motif (HRM) domains in its ECR. b, Two principle aGPCR activation modes have received evidence and either do (Dissociation model) or do not (Non-Dissociation model) rely on aGPCR heterodimer separation. c, The NRS consists of the ECR of a given adhesion GPCR including the autoproteolytically active GAIN domain with its GPCR proteolysis site (GPS) fused to the juxta- and transmembrane segment (JTS) of the Drosophila Notch receptor and an intracellular heterologous transcription-factor (TF) unit. The JTS contains the recognition sites for cleavage by metallo- and intramembrane proteases (S2–S4). The protein sequence at the GPS used in the Cirl-NRS is shown.