# Molecular and Functional Profiling of Gαi as an Intracellular pH Sensor

## TL;DR

This study reveals how Gαi, a protein involved in cell signaling, acts as a sensor for changes in intracellular pH and affects signaling processes.

## Contribution

The paper identifies a pH-sensing network in Gαi and shows how pH changes alter its structure and signaling function.

## Key findings

- Changes in pH from 6.8 to 7.5 cause structural and stability changes in Gαi-GDP.
- Modulating intracellular pH affects Gαi-Gβγ release in HEK293 cells.
- Key residues in the pH-sensing network were used to create mimetics that reduce Gαi-Gβγ release.

## Abstract

Heterotrimeric G proteins (Gα, Gβ and Gγ) act downstream of G-protein-coupled receptors (GPCRs) to mediate signaling pathways that regulate various physiological processes and human disease conditions. Previously, human Gαi and its yeast homolog Gpa1 have been reported to function as intracellular pH sensors, yet the pH sensing capabilities of Gαi and the underlying mechanism remain to be established. Herein, we identify a pH sensing network within Gαi, and evaluate the consequences of pH modulation on the structure and stability of the G-protein. We find that changes over the physiological pH range significantly alter the structure and stability of Gαi-GDP, with the protein undergoing a disorder-to-order transition as the pH is raised from 6.8 to 7.5. Further, we find that modulation of intracellular pH in HEK293 cells regulates Gαi-Gβγ release. Identification of key residues in the pH-sensing network allowed the generation of low pH mimetics that attenuate Gαi-Gβγ release. Our findings, taken together, indicate that pH-dependent structural changes in Gαi alter the agonist-mediated Gβγ dissociation necessary for proper signaling.