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Receptor inactivation by dye-neuropeptide conjugates. 3. Comparative binding of dye-neuropeptide conjugates to FMRFamide receptors of Helix aspersa and Loligo pealei |
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| Authors: | Jeffery J Feigenbaum Milind D Choubal David S Crumrine Jeffrey R Kanofsky Kemal Payza |
| Affiliation: | * Department of Research and Development, American Institute of Biotechnology, Elk Grove Village, IL 60007, USA ? Department of Chemistry, Loyola University, Chicago, IL 60626, USA ? Department of Medicine, Loyola University Stritch School of Medicine, Maywood, IL 60153, USA a Department of Biochemistry, Loyola University Stritch School of Medicine, Maywood, IL 60153, USA b Medical Service, Hines VA Hospital, Hines, IL 60141, USA § Laboratory of Cellular and Molecular Neurophysiology, NICHD, Bethesda, MD 20892, USA |
| Abstract: | Three neuropeptide analogues of FMRFamide (FMRFa) were covalently attached to a tethered derivative of methylene blue to form dye-neuropeptide conjugates. The comparative binding of the latter to FMRFa receptors was subsequently examined in both Helix aspersa (circumesophageal ganglia) and squid (optic lobe membrane). In Helix, the FMRFa analogue CFMRFamide (CFMRFa) inhibited the specific binding of the FMRFa ligand 125I]daYFnLRFa in a dose-dependent manner. Az-CFMRFa, one of the dye-neuropeptide conjugates, also dose-dependently inhibited the specific binding of 125I]daYFnLRFa. Moreover, their potencies equaled or exceeded that of FMRFamide. In squid, the binding of CFMRFa and FMRFa was similar. However, the dye-neuropeptide conjugate (IC50 of 14 nM) was about 44-fold less potent than FMRFa. The conjugates were synthesized as part of a study seeking to target and inactivate preselected receptors with heretofore unattainable selectivity and permanence. |
| Keywords: | Dye FMRFamide Analogues Neuropeptide Dye-neuropeptide conjugates Specific binding to FMRFamide receptors Helix aspersa Loligo pealei |
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