title: Protons Trigger Mitochondrial Flashes.
abstract: Emerging evidence indicates that mitochondrial flashes (mitoflashes) are highly conserved elemental mitochondrial signaling events. However, which signal controls their ignition and how they are integrated with other mitochondrial signals and functions remain elusive. In this study, we aimed to further delineate the signal components of the mitoflash and determine the mitoflash trigger mechanism. Using multiple biosensors and chemical probes as well as label-free autofluorescence, we found that the mitoflash reflects chemical and electrical excitation at the single-organelle level, comprising bursting superoxide production, oxidative redox shift, and matrix alkalinization as well as transient membrane depolarization. Both electroneutral H(+)/K(+) or H(+)/Na(+) antiport and matrix proton uncaging elicited immediate and robust mitoflash responses over a broad dynamic range in cardiomyocytes and HeLa cells. However, charge-uncompensated proton transport, which depolarizes mitochondria, caused the opposite effect, and steady matrix acidification mildly inhibited mitoflashes. Based on a numerical simulation, we estimated a mean proton lifetime of 1.42 ns and diffusion distance of 2.06 nm in the matrix. We conclude that nanodomain protons act as a novel, to our knowledge, trigger of mitoflashes in energized mitochondria. This finding suggests that mitoflash genesis is functionally and mechanistically integrated with mitochondrial energy metabolism.
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China. Electronic address: xianhua@pku.edu.cn.
authors.forename: Xianhua
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Aerospace Medicine, The Fourth Military Medical University, Xi'an, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Zhanglong
authors.initials: Z
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Beibei
authors.initials: B
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Rufeng
authors.initials: R
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Rongkang
authors.initials: R
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Hou
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Chongshu
authors.initials: C
authors.lastname: Jian
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Jiejia
authors.initials: J
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China.
authors.forename: Yanru
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Aerospace Medicine, The Fourth Military Medical University, Xi'an, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, Institute of Molecular Medicine, Peking University, Beijing, China. Electronic address: chengp@pku.edu.cn.
authors.forename: Heping
authors.initials: H
authors.lastname: Cheng
mesh_terms: D000818:Animals; D004734:Energy Metabolism / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D011522:Protons; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007476:Ionophores; D011522:Protons