The relaxin receptor RXFP1 signals through a mechanism of autoinhibition

• Published in: bioRxiv
• Main Authors: Erlandson, Sarah C, Rawson, Shaun, Osei-Owusu, James, Brock, Kelly P, Liu, Xinyue, Paulo, Joao A, Mintseris, Julian, Gygi, Steven P, Marks, Debora S, Cong, Xiaojing, Kruse, Andrew C
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 19.09.2022
• Subjects: Agonists; Drug development; Electron microscopy; G protein-coupled receptors; Guanine nucleotide-binding protein; Patent applications; Proteins; Relaxin; Signal transduction
• DOI: 10.1101/2022.01.22.477343

The relaxin family peptide receptor 1 (RXFP1) is the receptor for relaxin-2, an important regulator of reproductive and cardiovascular physiology. RXFP1 is a multi-domain G protein-coupled receptor (GPCR) with an ectodomain consisting of an LDLa module and leucine-rich repeats. The mechanism of RXFP1 signal transduction is clearly distinct from that of other GPCRs, but remains very poorly understood. Here, we present the cryo-electron microscopy structure of active-state human RXFP1, bound to a single-chain version of the endogenous agonist relaxin-2 and to the heterotrimeric Gs protein. Evolutionary coupling analysis and structure-guided functional experiments reveal that RXFP1 signals through a mechanism of autoinhibition, wherein the receptor's extracellular loop 2 occupies the orthosteric site in the active state but is inhibited by the ectodomain in the absence of relaxin-2. Our results explain how an unusual GPCR family functions, providing a path to rational drug development targeting the relaxin receptors. Competing Interest Statement A.C.K. and S.C.E are inventors on a patent application for engineered single-chain relaxin proteins. A.C.K. is a co-founder and consultant for Tectonic Therapeutic and Seismic Therapeutic and for the Institute for Protein Innovation, a non-profit research institute. Footnotes * Addition of new data regarding the small-molecule agonist ML290, as well as other minor revisions.