1
|
Jahan A, Akter MT, Takemoto K, Oura T, Shitara A, Semba S, Nezu A, Suto S, Nagai T, Tanimura A. Insertion of circularly permuted cyan fluorescent protein into the ligand-binding domain of inositol 1,4,5-trisphosphate receptor for enhanced FRET upon binding of fluorescent ligand. Cell Calcium 2022; 108:102668. [PMID: 36335765 DOI: 10.1016/j.ceca.2022.102668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 10/22/2022] [Accepted: 10/25/2022] [Indexed: 01/25/2023]
Abstract
Binding of fluorescent ligand (FL) to the cyan fluorescent protein (CFP)-coupled ligand-binding domain of the inositol 1,4,5-trisphosphate (IP3) receptor (CFP-LBP) produces fluorescence (Förster) resonance energy transfer (FRET). A competitive fluorescent ligand assay (CFLA), using the FRET signal from competition between FLs and IP3, can measure IP3 concentration. The FRET signal should be enhanced by attaching a FRET donor to an appropriate position. Herein, we inserted five different circularly permuted CFPs in the loop between the second and third α-helices to generate membrane-targeted fluorescent ligand-binding proteins (LBPs). Two such proteins, LBP-cpC157 and LBP-cpC173, localized at the plasma membrane, displayed FRET upon binding the high-affinity ligand fluorescent adenophostin A (F-ADA), and exhibited a decreased fluorescence emission ratio (480 nm / 535 nm) by 1.6- to 1.8-fold that of CFP-LBP. In addition, binding of a fluorescent low-affinity ligand (F-LL) also reduced the fluorescence ratio in a concentration-dependent manner, with EC50 values for LBP-cpC157 and LBP-cpC173 of 34.7 nM and 27.6 nM, respectively. These values are comparable to that with CFP-LBP (29.2 nM), indicating that insertion of cpC157 and cpC173 did not disrupt LBP structure and function. The effect of 100 nM F-LL on the decrease in fluorescence ratio was reversed upon addition of IP3, indicating binding competition between F-LL and IP3. We also constructed cytoplasmic fluorescent proteins cyLBP-cpC157 and cyLBP-cpC173, and bound them to DYK beads for imaging analyses. Application of F-ADA decreased the fluorescence ratio of the beads from the periphery to the center over 3 - 5 min. Application of F-LL also decreased the fluorescence ratio of cyLBP-cpC157 and cyLBP-cpC173 by 20-25%, and subsequent addition of IP3 recovered the fluorescence ratio in a concentration-dependent manner. The EC50 value and Hill coefficient obtained by curve fitting against the IP3-dependent recovery of fluorescence ratio can be used to estimate the IP3 concentration.
Collapse
Affiliation(s)
- Azmeree Jahan
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Mst Tahmina Akter
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Kiwamu Takemoto
- Department of Biochemistry, Mie University, Graduate School of Medicine, Mie, Japan
| | - Tai Oura
- Laboratory of Organic Chemistry for Drug Development, Faculty of Pharmaceutical Sciences, Hokkaido University, Hokkaido, Japan
| | - Akiko Shitara
- Department of Pharmacology, Asahi University School of Dentistry, Aichi, Japan
| | - Shingo Semba
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Akihiro Nezu
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Satoshi Suto
- Laboratory of Organic Chemistry for Drug Development, Faculty of Pharmaceutical Sciences, Hokkaido University, Hokkaido, Japan
| | - Takeharu Nagai
- Department of Biomolecular Science and Engineering, SANKEN (The Institute of Scientific and Industrial Research) Osaka University, Osaka, Japan
| | - Akihiko Tanimura
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
| |
Collapse
|