# Identification of the direct effector of the major brain G protein, G(alpha)o

> **NIH NIH F31** · YALE UNIVERSITY · 2022 · $46,752

## Abstract

Project Summary
My thesis project aims to clarify the signaling mechanism of the most abundant Gα protein subunit in the brain,
Gαo. Most neurotransmitters can bind to and activate G Protein Coupled Receptors (GPCRs) that signal through
Gαo, and alterations in Gαo signaling have been implicated in a number of neurological disorders. GPCRs
activate Gαo by promoting exchange of a bound GDP for GTP. This causes the dissociation of the Gβγ subunits
from Gαo and potentially allows both Gαo and Gβγ to bind and modulate the behavior different target molecules,
known as effectors. Genetic studies show that Gαo functions to prevent the release of neurotransmitters, but the
molecular details of how this occurs remains unclear, largely because the effector(s) that Gαo binds to and
regulates remain unknown. While some field have speculated that Gαo may simply serve to release the Gβγ
dimer to carry out signaling, studies in C. elegans refute this idea and suggest that Gαo must directly signal
through its own effectors. I hypothesize that Gαo signals by directly binding effector protein(s) and that identifying
and analyzing these effectors will be the key to understanding signaling by the major G protein of the brain. I
have employed immunopurification of activated and inactive Gαo protein complexes from mouse brain followed
by mass spectrometry to identify candidate Gαo effector molecules. I have already generated a large set of mass
spectrometry data and have identified the relatively unstudied Ras GTPase activators Rasa2/3 as strong
candidates to be the long-sought Gαo effectors. In this proposal I will use in vitro and in vivo experimental
approaches to characterize the interaction between Gαo and Rasa2/3.
My first is aim is to characterize the biochemical interactions between G⍺o and Rasa2/3 using purified
proteins. I will purify Gαo and Rasa2/3 as well as a control Rasa-binding protein and a control Gαo-GTP binding
protein. I will measure the binding affinities of active and inactive Gαo for Rasa2/3 and determine if the small-
molecule ligands of Rasa2/3, Ca2+ and IP3, alter this binding. I will map the binding interface of Rasa2/3 for Gαo.
My second aim is to use C. elegans genetics to analyze the functions of GAP-1, the close C. elegans
ortholog of mammalian Rasa proteins, to determine if and how it functions in Gαo signaling in vivo. I
have obtained a null mutant gap-1 and will analyze to determine if it phenocopies aspects of the already
extensively-characterized effects of Gαo mutations on specific behaviors in C. elegans. I will also determine
which neurons express gap-1 and direct my analysis to functions of those neurons. I will use double-mutant
studies to understand the in vivo functional relationship between Gαo, GAP-1, and Ras.

## Key facts

- **NIH application ID:** 10535634
- **Project number:** 1F31NS125953-01A1
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Halie Adesin Sonnenschein
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $46,752
- **Award type:** 1
- **Project period:** 2022-07-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10535634

## Citation

> US National Institutes of Health, RePORTER application 10535634, Identification of the direct effector of the major brain G protein, G(alpha)o (1F31NS125953-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10535634. Licensed CC0.

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