Molecular mechanism of AMD3100 antagonism in the CXCR4 receptor: transfer of binding site to the CXCR3 receptor.
AMD3100 is a symmetric bicyclam, prototype non-peptide antagonist of the CXCR4 chemokine receptor. Mutational substitutions at 16 positions located in TM-III, -IV, -V, -VI, and -VII lining the main ligand-binding pocket of the CXCR4 receptor identified three acid residues: Asp(171) (AspIV:20), Asp(262) (AspVI:23), and Glu(288) (GluVII:06) as the main interaction points for AMD3100. Molecular modeling suggests that one cyclam ring of AMD3100 interacts with Asp(171) in TM-IV, whereas the other ring is sandwiched between the carboxylic acid groups of Asp(262) and Glu(288) from TM-VI and -VII, respectively. Metal ion binding in the cyclam rings of AMD3100 increased its dependence on Asp(262) and provided a tighter molecular map of the binding site, where borderline mutational hits became clear hits for the Zn(II)-loaded analog. The proposed binding site for AMD3100 was confirmed by a gradual build-up in the rather distinct CXCR3 receptor, for which the compound normally had no effect. Introduction of only a Glu at position VII:06 and the removal of a neutralizing Lys residue at position VII:02 resulted in a 1000-fold increase in affinity of AMD3100 to within 10-fold of its affinity in CXCR4. We conclude that AMD3100 binds through interactions with essentially only three acidic anchor-point residues, two of which are located at one end and the third at the opposite end of the main ligand-binding pocket of the CXCR4 receptor. We suggest that non-peptide antagonists with, for example, improved oral bioavailability can be designed to mimic this interaction and thereby efficiently and selectively block the CXCR4 receptor.
Rosenkilde
Mette M
MM
Department of Pharmacology, University of Copenhagen, The Panum Institute, DK-2200 Copenhagen, Denmark. rosenkilde@molpharm.dk
Gerlach
Lars-Ole
LO
Jakobsen
Janus S
JS
Skerlj
Renato T
RT
Bridger
Gary J
GJ
Schwartz
Thue W
TW
D019380:Anti-HIV Agents / Q000737:chemistry / Q000494:pharmacology*; D001596:Benzylamines; D001665:Binding Sites; D000080027:Cyclams; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D019718:Receptors, CXCR4 / Q000037:antagonists & inhibitors* / Q000737:chemistry; D015398:Signal Transduction
D019380:Anti-HIV Agents; D001596:Benzylamines; D000080027:Cyclams; D006571:Heterocyclic Compounds; D019718:Receptors, CXCR4; C088327:plerixafor