<em>Investigation of interactions occurring at the extracellular loops of RXFP1</em> — ASN Events
  1. Schedule
  2. Session Five - Poster Session A
  3. Investigation of interactions occurring at the extracellular loops of RXFP1

Investigation of interactions occurring at the extracellular loops of RXFP1 (#145)

Natalie A Diepenhorst 1 2 , Samantha Lagadia 1 , Paul R Gooley 1 , Martin J Stone 3 , Ross A D Bathgate 1 2
  1. Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia
  2. Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
  3. Biochemistry and Molecular Biology, Monash University, Clayton, VIC, Australia

The Relaxin family peptide receptor 1 (RXFP1), cognate receptor for relaxin, is a unique G-protein coupled receptors possessing large N-terminal domains consisting of 10 leucine rich repeats (LRRs) and a low density lipoprotein Class A (LDLa) module. Relaxin binding to this receptor involves a high affinity interaction within the LRRs in addition to a secondary interaction involving the extracellular loops (ELs) of the transmembrane domain. The ELs may additionally participate in LDLa mediated signaling but this is yet to be investigated.

This project aims to identify residues in the RXFP1 ELs involved in relaxin and LDLa binding by mounting them onto a soluble protein scaffold and mapping the specific ligand interactions using NMR. We have produced a soluble scaffold containing RXFP1 EL1 and EL2 and have conducted relaxin and LDLa module titrations using NMR to determine an interaction. These results show a clear interaction between RXFP1 loops on the scaffold and both relaxin and the LDLa module. Using a series of truncated scaffolds, we have also revealed the importance of EL1 within these interactions where by ligand binding was severely diminished in an EL2 only scaffold with the interaction being partially restored in an EL1 minimised scaffold.

This is the first evidence that the LDLa module from RXFP1 is able to interact with the ELs of RXFP1 and highlights the importance of EL1 in interactions with both relaxin and the LDLa module. Together, this deepens our understanding of RXFP1 activation.