# Identifying endogenous peptide ligands for orphan G protein-coupled receptors to explore their roles in CNS disorders

> **NIH NIH R21** · ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI · 2022 · $253,500

## Abstract

Project summary
G protein-coupled receptors (GPCRs) play many important roles in physiology and pathology. GPCRs are the
largest target of FDA approved drugs. Over 100 GPCRs are considered orphans because their endogenous
ligands have not yet been identified, which is necessary for understanding the physiological role of the GPCR
as well as their contribution to CNS disorders. A large fraction of GPCRs are activated by neuropeptides and/or
peptide hormones, and our hypothesis is that many of the orphan receptors are activated by peptides,
presumably novel peptides, because other investigators have screened established bioactive peptides against
orphan receptors. A large number of novel peptides have been identified by peptidomic studies, and functions
for these are not known and hence they are considered ‘orphan peptides’ – these are very likely to function as
bioactive peptides based on their tissue and cellular distribution, localization to the regulatory secretory pathway,
and high sequence conservation across species. Our laboratory has successfully deorphanized six different
orphan peptides in that we identified receptors that are activated by them. In this proposal, we will use a gain-of-
function and a loss of function strategy to identify and validate a larger list of orphan ‘neuropeptide-receptor’
pairs. Our aims are: To identify ‘orphan’ receptors activated by ‘orphan’ neuropeptides using a gain-of-
function strategy (Aim 1), and to validate orphan ‘receptor-neuropeptide’ pairs using secondary screens
including a loss-of-function strategy (Aim 2). In Aim 1 we will use the PRESTO-Tango GPCR kit to screen
orphan GPCRs with orphan peptides. The assay involves overexpression of the GPCRs in the kit in HTLA cells
and measuring peptide-mediated arrestin recruitment. We will screen, 83 validated orphan GPCRs available in
the PRESTO-Tango system with each of the 42 highly curated orphan peptides that fit many of the criteria for
being a bioactive neuropeptide. We have found that several of these peptides cause a rapid and robust increase
in intracellular Ca2+ levels in Neuro 2A neuroblastoma cells and therefore these peptides are excellent candidates
to test against a library of orphan receptors. In Aim 2 we will validate the ‘orphan-neuropeptide’ pairs using
secondary screens as well as with shRNA-mediated knockdown of the target receptor. The identification of
ligands for orphan receptors will provide essential insights into the physiological roles of the receptors as well as
facilitate structural studies investigating receptor-ligand binding sites that are fundamental to the development of
new therapeutics targeting the receptors.

## Key facts

- **NIH application ID:** 10532036
- **Project number:** 1R21DA058300-01A1
- **Recipient organization:** ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
- **Principal Investigator:** Lakshmi A Devi
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $253,500
- **Award type:** 1
- **Project period:** 2022-09-15 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10532036

## Citation

> US National Institutes of Health, RePORTER application 10532036, Identifying endogenous peptide ligands for orphan G protein-coupled receptors to explore their roles in CNS disorders (1R21DA058300-01A1). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10532036. Licensed CC0.

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