β-Arrestin1 and β-Arrestin2 Are Required to Support the Activity of the CXCL12/HMGB1 Heterocomplex on CXCR4

• Published in: Frontiers in immunology 2020-09, Vol.11, p.550824-550824
• Main Authors: D'Agostino, Gianluca, Artinger, Marc, Locati, Massimo, Perez, Laurent, Legler, Daniel F, Bianchi, Marco E, Rüegg, Curzio, Thelen, Marcus, Marchese, Adriano, Rocchi, Marco B L, Cecchinato, Valentina, Uguccioni, Mariagrazia
• Format: Article
• Language: English
• Subjects: Actins - chemistry; Actins - metabolism; beta-Arrestin 1 - genetics; beta-Arrestin 1 - metabolism; beta-Arrestin 2 - genetics; beta-Arrestin 2 - metabolism; cell migration; Chemokine CXCL12 - metabolism; Chemotaxis; CRISPR-Cas Systems; CXCL12; CXCL12/HMGB1 heterocomplex; CXCR4; Gene Editing; Gene Knockdown Techniques; HeLa Cells; HMGB1; HMGB1 Protein - metabolism; Humans; Immunology; Multiprotein Complexes - metabolism; Protein Binding; Protein Multimerization; Protein Transport; Receptors, CXCR4 - metabolism; β-arrestin
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2020.550824

The chemokine receptor CXCR4 plays a fundamental role in homeostasis and pathology by orchestrating recruitment and positioning of immune cells, under the guidance of a CXCL12 gradient. The ability of chemokines to form heterocomplexes, enhancing their function, represents an additional level of regulation on their cognate receptors. In particular, the multi-faceted activity of the heterocomplex formed between CXCL12 and the alarmin HMGB1 is emerging as an unexpected player able to modulate a variety of cell responses, spanning from tissue regeneration to chronic inflammation. Nowadays, little is known on the selective signaling pathways activated when CXCR4 is triggered by the CXCL12/HMGB1 heterocomplex. In the present work, we demonstrate that this heterocomplex acts as a CXCR4 balanced agonist, activating both G protein and β-arrestins-mediated signaling pathways to sustain chemotaxis. We generated β-arrestins knock out HeLa cells by CRISPR/Cas9 technology and show that the CXCL12/HMGB1 heterocomplex-mediated actin polymerization is primarily β-arrestin1 dependent, while chemotaxis requires both β-arrestin1 and β-arrestin2. Triggering of CXCR4 with the CXCL12/HMGB1 heterocomplex leads to an unexpected receptor retention on the cell surface, which depends on β-arrestin2. In conclusion, the CXCL12/HMGB1 heterocomplex engages the β-arrestin proteins differently from CXCL12, promoting a prompt availability of CXCR4 on the cell surface, and enhancing directional cell migration. These data unveil the signaling induced by the CXCL12/HMGB1 heterocomplex in view of identifying biased CXCR4 antagonists or agonists targeting the variety of functions it exerts.