1. POLArIS, a versatile probe for molecular orientation, revealed actin filaments associated with microtubule asters in early embryos
- Author
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Shalin B. Mehta, Mikako Shirouzu, Hirokazu Ishii, Sumio Terada, Naoki Sakai, Yuri Tomabechi, Keisuke Sato, Tomomi Tani, Kazuyoshi Chiba, Kenta Saito, Masahiko Kawagishi, and Ayana Sugizaki
- Subjects
Embryo, Nonmammalian ,Phage display ,Fluorophore ,Swine ,Green Fluorescent Proteins ,Fluorescence Polarization ,Microtubules ,Starfish ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Microtubule ,Microscopy ,Fluorescence microscope ,Animals ,Humans ,Mitosis ,Actin ,Fluorescent Dyes ,030304 developmental biology ,0303 health sciences ,Multidisciplinary ,Biological Sciences ,Molecular Imaging ,Actin Cytoskeleton ,Microscopy, Fluorescence ,chemistry ,Centrosome ,Biophysics ,LLC-PK1 Cells ,030217 neurology & neurosurgery ,Fluorescence anisotropy ,HeLa Cells - Abstract
Biomolecular assemblies govern the physiology of cells. Their function often depends on the changes in molecular arrangements of constituents, both in the positions and orientations. While recent advancements of fluorescence microscopy including super-resolution microscopy have enabled us to determine the positions of fluorophores with unprecedented accuracy, monitoring orientation of fluorescently labeled molecules within living cells in real-time is challenging. Fluorescence polarization microscopy (FPM) reports the orientation of emission dipoles and is therefore a promising solution. For imaging with FPM, target proteins need labeling with fluorescent probes in a sterically constrained manner, but due to difficulties in the rational three-dimensional design of protein connection, universal method for constrained tagging with fluorophore was not available. Here we report POLArIS, a genetically encoded and versatile probe for molecular orientation imaging. Instead of using a direct tagging approach, we used a recombinant binder connected to a fluorescent protein in a sterically constrained manner and can target arbitrary biomolecules by combining with phage-display screening. As an initial test case of POLArIS, we developed POLArISact, which specifically binds to F-actin in living cells. We confirmed that the orientation of F-actin can be monitored by observing cells expressing POLArISactwith FPM. In living starfish early embryos expressing POLArISact, we found actin filaments radially extending from centrosomes in association with microtubule asters during mitosis. By taking advantage of the genetically encoded nature, POLArIS can be used in a variety of living specimens including whole bodies of developing embryos and animals, and also expressed in a cell-type/tissue specific manner.
- Published
- 2020