Background：

Atypical chemokine receptor that controls chemokine levels and localization via high-affinity chemokine binding that is uncoupled from classic ligand-driven signal transduction cascades， resulting instead in chemokine sequestration， degradation， or transcytosis. Also known as interceptor or chemokine-scavenging receptor or chemokine decoy receptor. Acts as a receptor for chemokines including CCL2， CCL3， CCL3L1， CCL4， CCL5， CCL7， CCL8， CCL11， CCL13， CCL17， CCL22， CCL23， CCL24， SCYA2/MCP-1， SCY3/MIP-1-alpha， SCYA5/RANTES and SCYA7/MCP-3. Upon active ligand stimulation， activates a beta-arrestin 1 (ARRB1)-dependent， G protein-independent signaling pathway that results in the phosphorylation of the actin-binding protein cofilin (CFL1) through a RAC1-PAK1-LIMK1 signaling pathway. Activation of this pathway results in up-regulation of ACKR2 from endosomal compartment to cell membrane， increasing its efficiency in chemokine uptake and degradation. By scavenging chemokines in