Functional modulation of PTH1R activation and signaling by RAMP2

Abstract

Receptor-activity-modifying proteins (RAMPs) are ubiquitously expressed membrane proteins that associate with different G protein–coupled receptors (GPCRs), including the parathyroid hormone 1 receptor (PTH1R), a class B GPCR and an important modulator of mineral ion homeostasis and bone metabolism. However, it is unknown whether and how RAMP proteins may affect PTH1R function. Using different optical biosensors to measure the activation of PTH1R and its downstream signaling, we describe here that RAMP2 acts as a specific allosteric modulator of PTH1R, shifting PTH1R to a unique preactivated state that permits faster activation in a ligand-specific manner. Moreover, RAMP2 modulates PTH1R downstream signaling in an agonist-dependent manner, most notably increasing the PTH-mediated Gi3 signaling sensitivity. Additionally, RAMP2 increases both PTH- and PTHrP-triggered β-arrestin2 recruitment to PTH1R. Employing homology modeling, we describe the putative structural molecular basis underlying our functional findings. These data uncover a critical role of RAMPs in the activation and signaling of a GPCR that may provide a new venue for highly specific modulation of GPCR function and advanced drug design.

Elucidating the Interactome of G Protein-Coupled Receptors and Receptor Activity-Modifying Proteins

“…In recent study, Nemec and colleagues investigated the class B GPCR–RAMP interaction of PTH 1 receptor (PTH1R) and RAMP2 ( Nemec et al, 2022 ). They used a Förster resonance energy transfer (FRET) experiment with C-terminally tagged PTH1R (mCitrine, acceptor) and RAMPs (mTurquoise2, donor) to show that PTH1R interacts with RAMP2, but not with RAMP1 or RAMP3.…”

Itch receptor MRGPRX4 interacts with the receptor activity–modifying proteins

“…RAMP2 has been reported to have pleiotropic effects on G protein activation and β-arrestin recruitment ( 13 ). For example, it promotes β-arrestin recruitment to CALCRL and parathyroid hormone 1 receptor but has no effect on β-arrestin recruitment to receptors such as the secretin receptor ( 13 , 30 , 31 , 32 ). Conversely, RAMP2 coexpression with the glucagon receptor (GCGR) abolishes β-arrestin recruitment, promotes enhanced basal and agonist-dependent GCGR internalization, and attenuates Gq activation while increasing intracellular Gs activation ( 33 , 34 ).…”

Itch receptor MRGPRX4 interacts with the receptor activity-modifying proteins (RAMPs)

“…RAMP2 has been reported to have pleiotropic effects on G protein activation and β-arrestin recruitment 15 . For example, it promotes β-arrestin recruitment to CALCRL and parathyroid hormone 1 receptor (PTH1R) but has no effect on β-arrestin recruitment to receptors such as the secretin receptor (SCTR) 15, 24–26 . Conversely, RAMP2 co-expression with the glucagon receptor (GCGR) abolishes β-arrestin recruitment, promotes enhanced basal and agonist-dependent GCGR internalization, and attenuates Gq activation while increasing intracellular Gs activation 27, 28 .…”