# Regulation of the metastasis promoting chemokine receptor ACKR3 by GPCR kinases, Gβγ and arrestins

> **NIH NIH R01** · PURDUE UNIVERSITY · 2021 · $644,675

## Abstract

PROJECT SUMMARY
Chemokines control the migration and localization of leukocytes and play fundamental roles in regulating
immune and inflammatory responses. One such chemokine, CXCL12, promotes multiple steps in the growth of
many primary tumors and progression to metastasis by binding to C-X-C chemokine receptor type 4 (CXCR4)
and atypical chemokine receptor 3 (ACKR3), which are upregulated in many cancers. Unlike most G protein-
coupled receptors (GPCRs), CXCL12-bound ACKR3 signals only via arrestins. In response to CXCL12,
ACKR3 is phosphorylated by intracellular GPCR kinases (GRKs) which subsequently recruit arrestins. The
arrestins serve as scaffolds that promotes growth pathways critical for cell survival, proliferation, and migration.
Arrestins also drive receptor internalization, during which CXCL12 is trafficked to lysosomes and degraded.
Afterwards, the empty receptor is recycled to the cell surface where it maintains a relatively stable
concentration. This process results in the "scavenging" or uptake of CXCL12 from the extracellular space and
is important for maintaining the responsiveness of CXCR4-expressing cells in the context of normal physiology
as well as tumor metastasis. In this proposal, the Tesmer and Handel labs, with deep expertise in GRKs and
chemokine receptor structure and function, respectively, join forces to better understand the molecular
mechanisms underlying ACKR3 phosphorylation by different GRKs, how arrestins interact with the resulting
phosphorylation “barcodes” installed in the C-terminus of the receptor, and what the cellular consequences
are. They have discovered that GRK2 and GRK5 phosphorylate activated ACKR3 at distinct regions of its
cytoplasmic tail. Moreover, phosphorylation enhances binding to both arrestin2 and 3. Arrestin2 recruitment
has not been reported before, and thus its functional significance remains to be elucidated. They have further
isolated complexes of ACKR3 with both arrestin as well as with GRK2–Gthat are of suitable quality for high
resolution cryo-electron microscopy (cryo-EM) reconstructions and have shown that G subunits alone can
form a strong interaction with ACKR3 of unknown function. In Aim1, cryo-EM structures of CXCL12-activated
ACKR3 will be determined in complex with various GRKs, with focus on GRK2, and with G. In Aim2, cryo-
EM will be used to examine arrestin complexes with phosphorylated ACKR3. In Aim 3, hypothesis driven cell-
based assays of ACKR3 function and unbiased mass spectrometry approaches will be used to systematically
investigate mechanisms by which these proteins control arrestin-mediated signaling and scavenging by
ACKR3 and determine if there is specific GRK and arrestin isoform control of ACKR3 function. The successful
conclusion of this proposal will result in the first structure of an atypical chemokine receptor in complex with its
intracellular signaling partners as well as unprecedented insights into the molecular mechanisms of a
therapeutica...

## Key facts

- **NIH application ID:** 10162570
- **Project number:** 5R01CA254402-02
- **Recipient organization:** PURDUE UNIVERSITY
- **Principal Investigator:** Tracy M Handel
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $644,675
- **Award type:** 5
- **Project period:** 2020-06-01 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10162570

## Citation

> US National Institutes of Health, RePORTER application 10162570, Regulation of the metastasis promoting chemokine receptor ACKR3 by GPCR kinases, Gβγ and arrestins (5R01CA254402-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10162570. Licensed CC0.

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