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MODIFIED CELL SIGNALING WITH MULTIVALENT LIGANDS TARGETING INDEPENDENT GPCR'S
Author(s) -
Weber Craig,
Brabez Nabila,
Vagner Josef,
Hruby Victor J,
Gillies Robert J,
Lynch Ronald
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.1064.8
Subject(s) - receptor , cholecystokinin , g protein coupled receptor , chemistry , cholecystokinin receptor , ligand (biochemistry) , signal transduction , microbiology and biotechnology , cell , biophysics , monomer , biochemistry , biology , organic chemistry , polymer
Ligands composed of multiple fragments of melanotropin ligand (MSH‐4) exhibit increased apparent binding affinity and signaling relative to the low affinity monomer; binding affinity of trivalent MSH‐4 was >350X higher than the monomer. To maintain the improved binding affinity and signaling while enhancing specificity of targeting, we developed a heterobivalent ligand (HBL) of MSH‐7 linked to cholecystokinin (CCK‐6). In cells with both receptors, the K d of the HBL was ~5 nM compared to > 250 nM when the MSH receptor was blocked with cold NDP‐MSH (i.e., monovalent CCK binding). At <5 nM HBL, binding to cells with only one receptor was negligible, demonstrating high specificity. Monomeric MSH‐7 elevated cAMP while CCK‐6 increased cell Ca 2+ . In the presence of both monomeric CCK and MSH, cAMP was elevated, but the Ca 2+ response was abolished, indicating feedback inhibition via cAMP. When cells were treated with the HBL, cAMP production was elevated whereas the Ca 2+ response to the HBL was attenuated by only 30% relative to monovalent CCK. This level of decrease in Ca 2+ response was similar to the effect of the HBL on cells expressing only the CCK receptor. The ability of the HBL to activate signaling is further evidence that the HBL binds to and activates both receptors. Moreover, the high selectivity and binding affinity coupled with altered signaling may be a useful pharmacological property of these new multivalent ligands.