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Modulation of the CXC chemokine receptor 4 agonist activity of ubiquitin through C-terminal protein modification. Biochemistry 2013 Jun 18;52(24):4184-92



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Scopus ID

2-s2.0-84879247089   18 Citations


Extracellular ubiquitin has recently been described as a CXC chemokine receptor (CXCR) 4 agonist. Studies on the structure-function relationship suggested that the C-terminus of ubiquitin facilitates CXCR4 activation. It remains unknown, however, whether C-terminal processing of ubiquitin could be biologically relevant and whether modifications of the ubiquitin C-terminus can modulate CXCR4 activation. We show that C-terminal truncated ubiquitin antagonizes ubiquitin and stromal cell-derived factor (SDF)-1α induced effects on cell signaling and function. Reduction of cell surface expression of insulin degrading enzyme (IDE), which cleaves the C-terminal di-Gly of ubiquitin, enhances ubiquitin induced reduction of cAMP levels in BV2 and THP-1 cells, but does not influence changes in cAMP levels in response to SDF-1α. Reduction of cell surface IDE expression in THP-1 cells also increases the chemotactic activity of ubiquitin. As compared with native ubiquitin, C-terminal Tyr extension of ubiquitin results in reduced CXCR4 mediated effects on cellular cAMP levels and abolishes chemotactic activity. Replacement of C-terminal di-Gly of ubiquitin with di-Val or di-Arg enhances CXCR4 mediated effects on cAMP levels and the di-Arg substitution exerts increased chemotactic activity, when compared with wild type ubiquitin. The chemotactic activities of the di-Val and di-Arg mutants and their effects on cAMP levels can be antagonized with C-terminal truncated ubiquitin. These data suggest that the development of CXCR4 ligands with enhanced agonist activities is possible and that C-terminal processing of ubiquitin could constitute a biological mechanism, which regulates termination of receptor signaling.

Author List

Tripathi A, Saini V, Marchese A, Volkman BF, Tang WJ, Majetschak M


Adriano Marchese PhD Professor in the Biochemistry department at Medical College of Wisconsin
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

Cell Line
Cell Membrane
Cell Separation
Chemokine CXCL12
Cyclic AMP
Flow Cytometry
Gene Silencing
Protein Binding
Protein Structure, Tertiary
RNA, Small Interfering
Receptors, CXCR4
Signal Transduction
Structure-Activity Relationship