51. A novel fluorescent method employing the FRET-based biosensor 'LIBRA' for the identification of ligands of the inositol 1,4,5-trisphosphate receptors
- Author
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Takao Morita, Akihiko Tanimura, Yosuke Tojyo, Akiko Shitara, and Akihiro Nezu
- Subjects
Chemistry ,Mutant ,Biophysics ,Receptors, Cytoplasmic and Nuclear ,Biosensing Techniques ,Saponins ,Ligands ,Biochemistry ,Fluorescence ,Cell Line ,chemistry.chemical_compound ,Förster resonance energy transfer ,Competitive antagonist ,Fluorescence Resonance Energy Transfer ,Inositol 1,4,5-Trisphosphate Receptors ,Inositol ,Calcium Channels ,Receptor ,Molecular Biology ,Biosensor - Abstract
LIBRA is a fluorescent biosensor of inositol 1,4,5-trisphosphate (IP 3 ) and is composed of the ligand-binding domain of the rat type 3 IP 3 receptor and cyan and yellow fluorescent proteins. We examined the responses of LIBRA and its IP 3 -insensitive mutant LIBRA-N to compounds known to inhibit IP 3 -induced Ca 2+ release. Heparin, a competitive antagonist of IP 3 receptors, increased the emission ratio of LIBRA but not that of LIBRA-N. In contrast, 2-aminoethoxydiphenyl borate, a known non-competitive inhibitor of IP 3 receptor, decreased the emission ratios of both LIBRA and LIBRA-N. Thus, the concurrent use of LIBRA-N with LIBRA identifies nonspecific responses. These results indicate that LIBRA and its mutant control can be used to detect specific agonists and antagonists of IP 3 receptors. We also demonstrate the utility of LIBRA and LIBRA-N in discriminating between specific and nonspecific responses in intact cells.
- Published
- 2006