Agonists for the Chemokine Receptor CXCR4

Abstract

The development of agonists for the chemokine receptor CXCR4 could provide promising therapeutic candidates. On the basis of previously forwarded two site model of chemokine-receptor interactions, we hypothesized that linking the agonistic N-terminus of SDF-1 to the T140 backbone would yield new high-affinity agonists of CXCR4. We developed chimeras with the agonistic SDF-1 N-terminus grafted to a T140 side chain and tested their binding affinity and chemotactic agonist activity. While chimeras with the peptide grafted onto position 12 of T140 remained high-affinity antagonists, those bearing the peptide on position 14 were in part agonists. One chimera was a full CXCR4 agonist with 25 nM affinity, and several chimeras showed low nanomolar affinities with partial agonist activity. Our results confirmed that we have developed high-affinity agonists of CXCR4.

Figure 1

Competition binding assay with ¹²⁵I-SDF-1α of analogues 7 and 10 containing varying SDF-1α chain lengths on HEK293 cells stably expressing human CXCR4 were carried out as described in the Experimental Procedures. IC₅₀ values were determined using GraphPad Prism 5 for Windows. These results are representative of at least three separate experiments.

Figure 2

Compounds 4, 6, and 10–12: Transwell migration assay where chemotaxis is expressed as % of REH cells initially seeded onto the Neuroprobe ChemoTx plate that did migrate to the bottom chamber. Experiments were carried out in triplicate, as described in the Experimental Procedures. Data were plotted using GraphPad Prism 5 for Windows. These results are mean values of at least three independent experiments.