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Functional and structural consequences of chemokine (C-X-C motif) receptor 4 activation with cognate and non-cognate agonists. Mol Cell Biochem 2017 Oct;434(1-2):143-151



Pubmed ID


Pubmed Central ID




Scopus ID

2-s2.0-85018295327   6 Citations


Chemokine (C-X-C motif) receptor 4 (CXCR4) regulates cell trafficking and plays important roles in the immune system. Ubiquitin has recently been identified as an endogenous non-cognate agonist of CXCR4, which activates CXCR4 via interaction sites that are distinct from those of the cognate agonist C-X-C motif chemokine ligand 12 (CXCL12). As compared with CXCL12, chemotactic activities of ubiquitin in primary human cells are poorly characterized. Furthermore, evidence for functional selectivity of CXCR4 agonists is lacking, and structural consequences of ubiquitin binding to CXCR4 are unknown. Here, we show that ubiquitin and CXCL12 have comparable chemotactic activities in normal human peripheral blood mononuclear cells, monocytes, vascular smooth muscle, and endothelial cells. Chemotactic activities of the CXCR4 ligands could be inhibited with the selective CXCR4 antagonist AMD3100 and with a peptide analogue of the second transmembrane domain of CXCR4. In human monocytes, ubiquitin- and CXCL12-induced chemotaxis could be inhibited with pertussis toxin and with inhibitors of phospholipase C, phosphatidylinositol 3 kinase, and extracellular signal-regulated kinase 1/2. Both agonists induced inositol trisphosphate production in vascular smooth muscle cells, which could be inhibited with AMD3100. In β-arrestin recruitment assays, ubiquitin did not sufficiently recruit β-arrestin2 to CXCR4 (EC > 10 μM), whereas the EC for CXCL12 was 4.6 nM (95% confidence interval 3.1-6.1 nM). Both agonists induced similar chemical shift changes in the C-H-heteronuclear single quantum correlation (HSQC) spectrum of CXCR4 in membranes, whereas CXCL11 did not significantly alter the C-H-HSQC spectrum of CXCR4. Our findings point towards ubiquitin as a biased agonist of CXCR4.

Author List

Eby JM, Abdelkarim H, Albee LJ, Tripathi A, Gao X, Volkman BF, Gaponenko V, Majetschak M


Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Chemokine CXCL12
Enzyme-Linked Immunosorbent Assay
Nuclear Magnetic Resonance, Biomolecular
Protein Conformation
Receptors, CXCR4
Signal Transduction
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