# RAMP-altered class B GPCR hormone binding and signaling

> **NIH NIH R01** · UNIVERSITY OF OKLAHOMA HLTH SCIENCES CTR · 2022 · $371,137

## Abstract

SUMMARY/ABSTRACT:
Three receptor activity-modifying proteins (RAMP1-3) in humans heterodimerize with the class B G protein-
coupled receptors (GPCRs) calcitonin receptor (CTR) and calcitonin-like receptor (CLR) and modulate their
responses to calcitonin (CT), amylin, calcitonin gene-related peptide (CGRP), and two adrenomedullin (AM)
peptide hormones. These have functions in bone remodeling (CT), regulation of food intake and blood glucose
(amylin), and regulation of blood and lymphatic vasculature function (CGRP and AM) by activating one or more
of seven receptors arising from CTR, CLR, and the RAMPs (6 heterodimers + CTR alone). The receptors are
drug targets for osteoporosis (CTR), diabetes and obesity (amylin receptors), migraine headache (CGRP
receptor), and cardiovascular and lymphatic system disorders (AM receptors). How RAMPs modulate CTR and
CLR ligand binding and signaling is incompletely understood. This limits our understanding of the molecular
basis for the diverse peptide actions in vivo and hinders drug development. Notably, there is growing evidence
that RAMPs interact with numerous GPCRs so understanding this model system will have broad impact. In
prior funding cycles we used biochemistry, pharmacology, and X-ray crystallography to reveal how CT, CGRP,
and the AM peptides bind their receptor extracellular domains (ECDs) and how the RAMP1/2 ECDs alter CLR
ECD peptide selectivity. Guided by these results we developed ultra high affinity CGRP and AM variants
including picomolar affinity antagonists and sustained signaling agonists that exhibit persistent cAMP signaling.
Herein we continue to define the mechanisms of RAMP modulation of CTR and CLR ligand binding and
signaling and further characterize our novel peptide variants, which may have therapeutic potential. In Aim 1
we define the kinetics of peptide binding at CGRP and AM receptors (CLR:RAMPs) and its relation to cAMP
signaling kinetics using biochemical and pharmacological assays (SPR and BRET kinetic methods). In Aim 2
we continue to define the structural bases for RAMP modulation of peptide binding to the CLR and CTR ECDs
using advanced molecular dynamics simulations and X-ray crystallography. In Aim 3 we employ a novel
biochemical assay to define how RAMPs modulate agonist and G protein coupling to CTR to enable amylin
signaling. Completion of this project will yield the following outcomes: 1) an understanding of how peptide
binding kinetics affects cAMP signaling kinetics for CGRP and AM receptors and the molecular basis for
sustained signaling of ultra high affinity variants, 2) a near complete high-resolution structural understanding of
calcitonin family peptide binding to their receptor ECDs including pathways of CGRP and AM peptide binding
and unbinding, and 3) clarification of longstanding amylin receptor pharmacology ambiguities and delineation
of how RAMPs modulate CTR. This project will advance our understanding of accessory membrane protein
modulation of GPCRs ...

## Key facts

- **NIH application ID:** 10488252
- **Project number:** 5R01GM104251-11
- **Recipient organization:** UNIVERSITY OF OKLAHOMA HLTH SCIENCES CTR
- **Principal Investigator:** Augen A Pioszak
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $371,137
- **Award type:** 5
- **Project period:** 2012-09-26 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10488252

## Citation

> US National Institutes of Health, RePORTER application 10488252, RAMP-altered class B GPCR hormone binding and signaling (5R01GM104251-11). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10488252. Licensed CC0.

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