Regulation of Endothelial Cell function by Integration of Gαi and β‐arrestin signaling at Atypical Chemokine Receptor 3
Bibliographic record
Abstract
Atypical Chemokine receptor 3 (ACKR3), also known as C‐X‐C chemokine receptor type 7 (CXCR7), is a G protein‐coupled receptor (GPCR) implicated in several physiological processes including leukocyte trafficking, cancer, and angiogenesis. Commonly co‐expressed with C‐X‐C chemokine receptor type 4 (CXCR4), ACKR3 is classified as an β‐arrestin‐biased “scavenger” receptor due to its lack of G‐protein signaling and its ability to efficiently internalize and degrade its ligands, CXCL11 and CXCL12. However, much is still unknown regarding ACKR3 signaling mechanisms and its implications on cellular physiology. Here we describe ongoing studies to characterize the mechanisms that underlie ACKR3 signaling and endothelial cell function. We demonstrated two ACKR3 specific agonists, WW36 and WW38, promote proliferation and migration of human umbilical vein endothelial cells (HUVECs). Surprisingly, we found that ACKR3‐promoted proliferation and migration was sensitive to pertussis toxin (PTX), suggesting the involvement of Gαi/o proteins at a receptor which does not canonically signal via G proteins. We also observed similar sensitivity to PTX on ERK activation in HUVECs. We hypothesized that these results may in part be explained by the recently described coordination of Gαi and β‐arrestin (βarr) to promote Gαi:βarr complex‐specific downstream signaling. In support of this hypothesis, we demonstrated the formation of a Gαi:βarr complex upon ACKR3 activation in a dose‐dependent manner. To characterize the necessary components in Gαi and βarr, we first developed active proximal polar core mutant and proximal finger loop βarr mutant and tested these at the prototypical class B Vasopressin 2 Receptor. Both mutants lead to considerable decrease in complex formation with the finger loop mutation nearly abolishing our split signal. Within the Gαi subfamily, we observed considerable differences in the ability to form complex, with Gαi2 and Gαi3 promoting less complex formation than Gαi1 and Gαo. We developed several Gαi mutants, hypothesizing that residues that differ between Gαi isoforms may impact Gαi:βarr formation. Using NanoBRET we demonstrated that these mutants impair complex formation, suggesting that they may be involved either via direct contacts with βarr or impacting Gαi conformation such that complex formation is no longer as favorable. These studies reveal a novel role for Gαi:βarr complexes in mediating ACKR3 function that contribute to endothelial cell biology. Additionally, these findings support an emerging paradigm in which G proteins and βarr coordinate their signaling downstream of GPCRs.
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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) | 0.000 | 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".