Characterization of ß-arrestins trafficking and signaling functions on G protein-coupled receptors
Bibliographic record
Abstract
The heptahelical G protein-coupled receptors (GPCRs) are the largest, most versatile superfamily of cell surface receptors and constitute the most common target for many therapeutic drugs. They participate in various physiological processes via signaling transduction, mainly induced by heterotrimeric G proteins. Following activation, these 7-transmembrane receptors recruit β-arrestin for endocytosis. Beta-arrestins will directlyassociate GPCRs to several components of the endocytic machinery, such as clathrin and adaptor protein 2 (AP-2), allowing the receptor to internalize. Over the years, β-arrestins were shown to also act as signaling adaptors upon binding to agonist-occupied GPCRs; however, the mechanism regulating receptor/β-arrestin complexes in endosomes was not yet addressed. Based on a previous study where we showed that β-arrestin serves as a scaffolding protein for several signaling effectors (e.g. MAPK) in the endosomes, we hypothesized that endosomal MAPK activity would be necessary to maintain the GPCR/β-arrestin-2 complex, thus regulating receptor trafficking. Our first study revealed a putative phosphorylating MAPK motif (Thr178) in β-arrestin-2 suggesting that endosomal MAPK activity is involved in such process. Using biochemical assays and FRAP (Fluorescence Recovery After Photobleaching) approach to assess the life-time of bradykinin B2 receptor (B2R)/β-arrestin-2 endosomal complexes, we showed that the MAPK putative site in β-arrestin-2 is involved in regulating the association between the arrestin and its receptor. The role of β-arrestin-2 ‘hinge’ domain was tested for such effect, and using arrestin mutants demonstrated distinct behaviours between β-arrestin-2 species on GPCRs trafficking and agonist mediated receptor signaling. This study highlights a strong correlation between MAPKsignaling and the regulation of endosomal GPCR/β-arrestin-2 interactions. In addition to the ‘hinge’ domain, structural studies showed that the polar core, as well as the arrestins loops, were also crucial for β-arrestin activation. Based on the crystal structure of β-arrestin-1, a virtual screen was then conducted in order to identify aselective pharmacological inhibitor of β-arrestin-2. Results showed a unique compound, namely UM0012685 which firstly, blocked V2-vasopressin receptor (V2R) endocytosis; Secondly, inhibited β-arrestin recruitment; Thirdly, decreased the stability of the receptor and β-arrestin-2 endosomal complexes and finally inhibited β-arrestin-2-dependent MAPK activation upon agonist stimulation of the V2R. This compound was also used as a tool to determine β-arrestins trafficking function on β2-adrenergic receptor (β2AR) recycling. These results uncover a better understanding of the underlying mechanism regulating β-arrestin in the endosomes as well as the intracellular trafficking modulation of GPCRs. Our findings also reveal a useful tool to investigate the multifunctional aspect of β-arrestins in the cell.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".