Natural nitration of CXCL12 reduces its signaling capacity and chemotactic activity in vitro and abrogates intra-articular lymphocyte recruitment in vivo
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Rik Janssens1,2, Anneleen Mortier1, Daiane Boff1,2, Vincent Vanheule1, Mieke Gouwy1, Charlotte Franck1,3, Olav Larsen3, Mette M. Rosenkilde3, Jo Van Damme1, Flávio A. Amaral2, Mauro M. Teixeira2, Sofie Struyf1, Paul Proost1
1Laboratory of Molecular Immunology, Department of Microbiology and Immunology, Rega Institute, KU Leuven, B-3000 Leuven, Belgium
2Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brasil
3Laboratory for Molecular Pharmacology, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, The Panum Institute, University of Copenhagen, DK-2200 Copenhagen, Denmark
Paul Proost, email: [email protected]
Keywords: chemokine, posttranslational modification, lymphocyte migration, extravasation, chemotaxis
Received: November 16, 2015 Accepted: August 13, 2016 Published: August 23, 2016
The chemokine CXCL12/stromal cell-derived factor-1 is important for leukocyte migration to lymphoid organs and inflamed tissues and stimulates tumor development. In vitro, CXCL12 activity through CXCR4 is abolished by proteolytic processing. However, limited information is available on in vivo effects of posttranslationally modified CXCL12. Natural CXCL12 was purified from the coculture supernatant of stromal cells stimulated with leukocytes and inflammatory agents. In this conditioned medium, CXCL12 with a nitration on Tyr7, designated [3-NT7]CXCL12, was discovered via Edman degradation. CXCL12 and [3-NT7]CXCL12 were chemically synthesized to evaluate the biological effects of this modification. [3-NT7]CXCL12 recruited β-arrestin 2 and phosphorylated the Akt kinase similar to CXCL12 in receptor-transfected cells. Also the affinity of CXCL12 and [3-NT7]CXCL12 for glycosaminoglycans, the G protein-coupled chemokine receptor CXCR4 and the atypical chemokine receptor ACKR3 were comparable. However, [3-NT7]CXCL12 showed a reduced ability to enhance intracellular calcium concentrations, to generate inositol triphosphate, to phosphorylate ERK1/2 and to induce monocyte and lymphocyte chemotaxis in vitro. Moreover, nitrated CXCL12 failed to induce in vivo extravasation of lymphocytes to the joint. In summary, nitration on Tyr7 under inflammatory conditions is a novel natural posttranslational regulatory mechanism of CXCL12 which may downregulate the CXCR4-mediated inflammatory and tumor-promoting activities of CXCL12.
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