title: Sustained accurate recording of intracellular acidification in living tissues with a photo-controllable bioluminescent protein.
abstract: Regulation of an intracellular acidic environment plays a pivotal role in biological processes and functions. However, spatiotemporal analysis of the acidification in complex tissues of living subjects persists as an important challenge. We developed a photo-inactivatable bioluminescent indicator, based on a combination of luciferase-fragment complementation and a photoreaction of a light, oxygen, and voltage domain from Avena sativa Phototropin1 (LOV2), to visualize temporally dynamic acidification in living tissue samples. Bioluminescence of the indicator diminished upon light irradiation and it recovered gradually in the dark state thereafter. The recovery rate was remarkably sensitive to pH changes but unsusceptible to fluctuation of luciferin or ATP concentrations. Bioluminescence imaging, taken as an index of the recovery rates, enabled long-time recording of acidification in apoptotic and autophagous processes in a cell population and an ischemic condition in living mice. This technology using the indicator is widely applicable to sense organelle-specific acidic changes in target biological tissues.
authors.affiliation: Department of Chemistry, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Hattori
authors.forename: Sanae
authors.initials: S
authors.lastname: Haga
authors.forename: Hideo
authors.initials: H
authors.lastname: Takakura
authors.forename: Michitaka
authors.initials: M
authors.lastname: Ozaki
authors.forename: Takeaki
authors.initials: T
authors.lastname: Ozawa
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000818:Animals; D018554:Avena / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents / Q000737:chemistry; D008163:Luminescent Measurements / Q000379:methods*; D051379:Mice; D008991:Monitoring, Physiologic / Q000379:methods*; D010100:Oxygen / Q000378:metabolism; D010775:Photic Stimulation; D056949:Phototropins / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D007202:Indicators and Reagents; D056949:Phototropins; D010100:Oxygen