Biology subjects

Blythe, E. E.

Publications and source records attributed to Blythe, E. E..

2 recordsLinked to original sources

bioRxiv2022

A discrete mode of endosomal GPCR signaling that does not require β-arrestin

Many GPCRs are now recognized to initiate a second phase of G protein (Gs) -dependent signaling through the cAMP cascade after endocytosis. A prevailing current view is that endocytosis-promoted signaling from GPCRs is inherently {beta}-arrestin-dependent because {beta}-arrestin is necessary for receptors to internalize and, for some GPCRs, it also promotes Gs activation on endosomes. Here we revise this view by showing that the vasoactive intestinal peptide receptor 1 (VIPR1), a prototypic secretin-family polypeptide hormone receptor, remains bound to {beta}-arrestin after endocytosis but does not require {beta}-arrestin either to internalize or to generate an endosomal signal. {beta}-arrestin instead resolves the endosomal signal into a temporally separated cAMP peak, and it does so by attenuating signaling from the plasma membrane without detectably affecting the endosomal response. The mechanistic basis for this location-specific difference in {beta}-arrestin function is the formation of distinct VIPR1/{beta}-arrestin complexes at each location. The signal-attenuating complex formed at the plasma membrane does not require GRK-mediated phosphorylation of receptors, while the signaling-neutral complex present on the endosome membrane, in contrast, is GRK-dependent. To our knowledge, the present results provide the first direct demonstration that endosomal GPCR signaling can occur in the complete absence of {beta}-arrestin. They also reveal a discrete role of {beta}-arrestin in sculpting the spatiotemporal profile of cellular GPCR - G protein signaling through the location-specific formation or remodeling of GPCR/{beta}-arrestin complexes.

cell biology↗

bioRxiv2022

Profiling the diversity of agonist-selective effects on the proximal proteome environment of G protein-coupled receptors

The mu opioid receptor (OR), a prototypic member of the large G protein-coupled receptor (GPCR) family, represents an important target of therapeutic and abused drugs. To date, most of our understanding of OR activity has focused on signal transducers and regulatory molecules including G proteins, GPCR kinases, and beta-arrestins. Yet it is clear that signaling through the OR is coordinated by additional proteins recruited into the proximal interaction network of the activated receptor, which have largely remained invisible given the lack of technologies to interrogate these networks systematically. Here, we implement a quantitative proteomics pipeline leveraging the chemical diversity of OR agonists and APEX-based proximity labeling to investigate the protein networks that underlie OR signaling. We leverage a novel computational framework to extract subcellular location, trafficking, and functional partners of GPCR activity from the proximity labeling datasets. Applying this unbiased, systematic approach to the OR, we demonstrate that opioid agonists exert differences in the OR proximal proteome mediated by endocytosis and subsequent endosomal sorting, exemplified by VPS35 and COMMD3. Moreover, we identify two novel OR network components, EYA4 and KCTD12, that are recruited into the receptor proximal network irrespective of the activating ligand and independent of receptor trafficking but based on receptor-triggered G protein activation. We provide functional evidence that these network components form a previously unrecognized buffering system for G protein activity which broadly modulates cellular GPCR signaling.

systems biology↗