The TRY‐motif in the Relaxin Family Peptide Receptor 3 (RXFP3) functions as a Molecular Switch Between DNA Damage Response and Cell Cycle Control

Abstract

The majority of Rhodopsin-like Class A G protein-coupled receptors (GPCRs) contain the conserved Aspartate–Arginine–Tyrosine (DRY) motif in transmembrane helix 3 (TM3). This DRY-motif is responsible for the presence of an ionic lock, consisting of a salt bridge between the positively charged R3.50 in TM3 and the negatively charged glutamic acid (E6.30) on TM6 in typical rhodopsin-like GPCRs. While the R3.50 is 96% conserved across all class A GPCRs, D3.49 and Y3.51 are 66, and 67% conserved respectively. This variance in D3.49 and Y3.51 residues potential identifies a locus for evolutionary modification of GPCR signaling. The relaxin family peptide receptor 3 (RXFP3), a Class A GPCR, which plays a crucial role in the aging process via providing resilience to stress, possesses a natural variant of the DRY motif, where Aspartate is replaced by Threonine, creating a TRY motif. This variation enhances the ligand-independent activity of the RXFP3 receptor. We investigated how this natural variation may be implicated in its stress-resistance role through selective mutation of the TRY motif back to a canonical DRY sequence. Using an unbiased quantitative proteomic perturbation response approach, we found that protein network analysis revealed that DNA damage repair functions are supported by the presence of a TRY motif while reversion to a DRY sequence in the RXFP3 diverts signaling activity instead to cell-cycle/cellular senescence control. Thus it is likely that the RXFP3 has been naturally mutated to a TRY sequence to promote its anti-aging stress sensor role.