title: Microscopic visualization of metabotropic glutamate receptors on the surface of living cells using bifunctional magnetic resonance imaging probes.
abstract: A series of bimodal metabotropic glutamate-receptor targeted MRI contrast agents has been developed and evaluated, based on established competitive metabotropic Glu receptor subtype 5 (mGluR5) antagonists. In order to directly visualize mGluR5 binding of these agents on the surface of live astrocytes, variations in the core structure were made. A set of gadolinium conjugates containing either a cyanine dye or a fluorescein moiety was accordingly prepared, to allow visualization by optical microscopy in cellulo. In each case, surface receptor binding was compromised and cell internalization observed. Another approach, examining the location of a terbium analogue via sensitized emission, also exhibited nonspecific cell uptake in neuronal cell line models. Finally, biotin derivatives of two lead compounds were prepared, and the specificity of binding to the mGluR5 cell surface receptors was demonstrated with the aid of their fluorescently labeled avidin conjugates, using both total internal reflection fluorescence (TIRF) and confocal microscopy.
authors.affiliation: Department of Chemistry and ‡School of Biological and Biomedical Sciences, Durham University , South Road, Durham DH1 3LE, England.
authors.forename: Anurag
authors.initials: A
authors.lastname: Mishra
authors.forename: Ritu
authors.initials: R
authors.lastname: Mishra
authors.forename: Sven
authors.initials: S
authors.lastname: Gottschalk
authors.forename: Robert
authors.initials: R
authors.lastname: Pal
authors.forename: Neil
authors.initials: N
authors.lastname: Sim
authors.forename: Joern
authors.initials: J
authors.lastname: Engelmann
authors.forename: Martin
authors.initials: M
authors.lastname: Goldberg
authors.forename: David
authors.initials: D
authors.lastname: Parker
mesh_terms: D001253:Astrocytes / Q000378:metabolism*; D003287:Contrast Media / Q000138:chemical synthesis*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D018613:Microscopy, Confocal / Q000379:methods; D008857:Microscopy, Interference / Q000379:methods; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*
chemical_list: D003287:Contrast Media; D018094:Receptors, Metabotropic Glutamate