# Conformational biosensors delineate endosomal G protein regulation by GPCRs

## TL;DR

This paper explores how GPCRs regulate G proteins on endosomes, revealing new mechanisms of signaling and selectivity.

## Contribution

The study identifies distinct GPCR-G protein coupling reactions at the plasma membrane and endosomes.

## Key findings

- Three Gs-coupled GPCRs redistribute Gαs from plasma membrane to endosomes without internalization.
- Active-state Gαs production on endosomes depends on GPCR internalization.
- GPCR coupling to Gs and Gq shows location bias between plasma membrane and endosomes.

## Abstract

Many GPCRs trigger a second phase of G protein-coupled signaling from endosomes after signaling from the plasma membrane, necessitating GPCRs to increase the concentration of active-state G proteins on the endosome membrane. How this is achieved remains unclear. Here, we show that three Gs-coupled GPCRs–the β2-adrenergic receptor, VIP-1 receptor, and adenosine 2B receptor–each trigger a net redistribution of Gαs from the plasma membrane to endosomes at native expression levels and without requiring receptor internalization. We then show that active-state Gαs production on endosomes, in contrast, is GPCR internalization-dependent. We further identify location bias in the selectivity of GPCR coupling between Gs and Gq on endosomes relative to the plasma membrane. We propose that endosomal Gs regulation involves discrete GPCR-G protein coupling reactions, one at the plasma membrane controlling Gs concentration and another at endosomes controlling Gs activity, and that GPCR endocytosis can switch signaling selectivity between G protein classes.

Many GPCRs signal from endosomes, which requires active G proteins at this location. Here, the authors describe how active Gαs accumulates on endosomes and reveal location-biased selectivity in GPCR-mediated G protein activation.