Regulation of superoxide flashes by transient and steady mitochondrial calcium elevations.
The mitochondria play essential roles in both intracellular calcium and reactive oxygen species signaling. As a newly discovered universal and fundamental mitochondrial phenomenon, superoxide flashes reflect transient bursts of superoxide production in the matrix of single mitochondria. Whether and how the superoxide flash activity is regulated by mitochondrial calcium remain largely unknown. Here we demonstrate that elevating mitochondrial calcium either by the calcium ionophore ionomycin or by increasing the bathing calcium in permeabilized HeLa cells increases superoxide flash incidence, and inhibition of the mitochondrial calcium uniporter activity abolishes the flash response. Quantitatively, the superoxide flash incidence is correlated to the steady-state mitochondrial calcium elevation with 1.7-fold increase per 1.0 ΔF/F 0 of Rhod-2 signal. In contrast, large mitochondrial calcium transients (e.g., peak ΔF/F 0 ∼ 2.8, duration ∼ 2 min) in the absence of steady-state elevations failed to alter the flash activity. These results indicate that physiological levels of sustained, but not transient, mitochondrial calcium elevation acts as a potent regulator of superoxide flashes, but its mechanism of action likely involves a multi-step, slow-onset process.
State Key Laboratory of Biomembrane and Membrane Biotechnology, Beijing Key Laboratory of Cardiometabolic Molecular Medicine, Institute of Molecular Medicine, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China.
ChongShu
C
Jian
TingTing
T
Hou
RongKang
R
Yin
HePing
H
Cheng
XianHua
X
Wang
D000814:Aniline Compounds; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D005456:Fluorescent Dyes; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006575:Heterocyclic Compounds, 3-Ring; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism*; D014966:Xanthenes
D000814:Aniline Compounds; D015220:Calcium Channels; D061207:Calcium Ionophores; C409648:Fluo 4; D005456:Fluorescent Dyes; D006575:Heterocyclic Compounds, 3-Ring; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014966:Xanthenes; C034703:mitochondrial calcium uniporter; C068483:rhod-2; D013481:Superoxides; D015759:Ionomycin; D002118:Calcium