CXCR7

CXCR7, currently designated atypical chemokine receptor 3 (ACKR3), is a seven-transmembrane chemokine receptor that functions as a regulator of chemokine availability and intracellular signaling within the CXCL12 axis^[1]. Unlike canonical chemokine receptors, CXCR7 lacks the conserved motif required for efficient G_i-protein coupling and is therefore classified as an atypical chemokine receptor with predominant β-arrestin-associated signaling properties^[1][2]. Mechanistically, CXCR7 binds CXCL12 with higher affinity than CXCR4 and modulates chemokine gradients through ligand sequestration, receptor internalization, and regulation of downstream signaling networks^[1][3]. The CXCL12/CXCR4/CXCR7 signaling system contributes to neural, vascular, and cardiac development, while also regulating cell migration, proliferation, and tissue remodeling processes^[1][4]. In disease models, elevated CXCR7 expression has been associated with hypoxia-responsive pathways, glioma progression, tumor-associated angiogenesis, and multiple cancer types in which CXCL12 signaling supports tumor growth and cellular survival^[1][5]. Compared with the closely related receptor CXCR4, CXCR7 displays distinct signaling behavior, acting primarily through β-arrestin-mediated mechanisms and chemokine scavenging while also modifying CXCR4-dependent cellular responses through receptor interaction^[1][2]. For experimental applications, the selective CXCR7 agonist CCX771 has been widely used to investigate receptor-specific functions because it binds CXCR7 with high affinity and does not interfere with CXCL12 binding to CXCR4^[1].