# Conformational Dynamics of G Protein-Coupled Receptors at the Single-Molecule Level

> **NIH NIH R35** · UNIVERSITY OF TENNESSEE KNOXVILLE · 2024 · $374,821

## Abstract

PROJECT SUMMARY/ABSTRACT
The overall goal of my research project is to understand how the dynamic behavior of human G protein-coupled
receptors (GPCRs) drives the assembly of GPCR complexes with drugs and partner signaling proteins at a
single-molecule level. GPCRs are sensory membrane proteins that recognize a wide array of hormones, drugs,
and neurotransmitters, representing the largest class of proteins targeted by FDA-approved therapeutics. The
energy landscape of GPCRs is complex and populated by multiple conformers with distinct functions and
structures. While the structures of some GPCR conformers have been characterized by x-ray crystallography
and cryo-EM, the lifetimes of these different conformations and their rates of exchange are mostly unknown. We
aim to map the energy landscape of GPCR complexes using single-molecule fluorescence (SMF), which enables
the investigation of GPCR dynamics in real-time and in environments that recapitulate the cellular milieu. In the
long term, we aim to apply this information to improve our understanding of how disease-associated mutations
alter these energy landscapes, which may ultimately guide the design of new therapeutics. This proposal aims
to apply SMF to map the energy landscapes of two human GPCRs. First, we will investigate the conformational
dynamics of a representative class A human GPCR, the A2A adenosine receptor (A2AAR). A2AAR provides an
important benchmark for single-molecule fluorescence studies and will enable us to compare our experimental
measurements of dynamics to computational predictions. Our studies will reveal both similarities and differences
in mechanisms of signaling between different class A GPCRs and will also show for the first time how lipids in
the bilayer membrane can act as allosteric modulators of GPCR function. In the second direction, we will use
SMF to study the conformational dynamics of the human glucagon receptor (GCGR). GCGR is a hormone-
binding class B GPCR that is activated by one of the central metabolites, glucagon. GCGR is critical to glucose
homeostasis and is a validated drug target for type 2 diabetes therapy. Crystal and cryo-EM structures of GCGR
have shown that the large extracellular domains appear to act in concert with the transmembrane domain to bind
hormones and small molecules, but the dynamics of ligand binding are as yet not understood. Our studies of
GCGR will reveal in real-time the mechanisms of ligand recognition by the extracellular domain and quantify
function-related dynamic fluctuations of the transmembrane domains. These studies will allow us to compare
the dynamics of complex formation with hormones and with small molecules to understand the role of the
extracellular domain in ligand recognition. This will help us understand how ligands with different chemical
structures and pharmacological efficacies affect the receptor activation pathways and will ultimately aid in the
design and screening of GPCR-targeted drugs with tailored ...

## Key facts

- **NIH application ID:** 10839846
- **Project number:** 5R35GM142946-04
- **Recipient organization:** UNIVERSITY OF TENNESSEE KNOXVILLE
- **Principal Investigator:** Rajan Lamichhane
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $374,821
- **Award type:** 5
- **Project period:** 2021-07-01 → 2026-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10839846

## Citation

> US National Institutes of Health, RePORTER application 10839846, Conformational Dynamics of G Protein-Coupled Receptors at the Single-Molecule Level (5R35GM142946-04). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10839846. Licensed CC0.

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