# Mechanisms of GPCR Signaling

> **NIH NIH R01** · STATE UNIVERSITY NEW YORK STONY BROOK · 2021 · $331,510

## Abstract

The light-activated visual receptor rhodopsin has provided the foundation for understanding the structure and
mechanism of G protein-coupled receptors (GPCRs). Nevertheless, there remain fundamental unanswered
questions about how these receptors work. Here, we target several basic questions that are relevant for
understanding their mechanism(s) of activation. The approach is primarily through structural measurements
using solid-state NMR spectroscopy. The existing crystal structures of these receptors provide a high-
resolution framework to study in detail the role of specific residues and motifs in receptor activation. Because
of the high conservation of residues between the visual and ligand-activated GPCRs, the emerging consensus
is that rather than being unique, the visual receptors provide a basis for understanding the common structural
and dynamic elements in these receptors. The general experimental strategy is to use solid-state NMR
spectroscopy in combination with mutational, optical and biochemical methods to target specific regions in the
inactive and active states of the dim-light receptor, rhodopsin. The goal is to understand in atomic detail the
interplay between specific signature, group-conserved and subfamily-conserved motifs in the activation
mechanism of rhodopsin and establish a common basis for the activation of other GPCRs.
Four specific aims address structure-function questions involving regions on the extracellular side of rhodopsin
(Aim 1) and within the transmembrane (TM) core and on the intracellular side of the receptor (Aim 2). In Aim 1,
we will establish the role of Trp6.48 – a key residue that mediates retinal isomerization and Schiff base
deprotonation with the conserved TM core of the receptor. In Aim 2, we address how retinal Schiff base
deprotonation leads to activation. The working model is that there are two triggers, one electrostatic and one
steric in nature. We target the conserved TM core of rhodopsin composed of interlocking signature and group-
conserved residues. The working model is that the TM core is composed of two packing clusters and two
activation switches. These provide stable and flexible elements to the receptor, respectively. In Aim 3, we
focus on the G protein and its interactions with residues on the intracellular surface of the active Meta II
intermediate. In this aim, we address the role of the membrane environment in receptor stability and activation.
Finally, in Aim 4 we use the information garnered above and from past studies to determine the basis for two
retinal diseases, congenital stationary night blindness and autosomal dominant retinitis pigmentosa.

## Key facts

- **NIH application ID:** 10240655
- **Project number:** 5R01GM129012-04
- **Recipient organization:** STATE UNIVERSITY NEW YORK STONY BROOK
- **Principal Investigator:** STEVEN Owen SMITH
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $331,510
- **Award type:** 5
- **Project period:** 2018-09-15 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10240655

## Citation

> US National Institutes of Health, RePORTER application 10240655, Mechanisms of GPCR Signaling (5R01GM129012-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10240655. Licensed CC0.

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