Mitochondria are intracellular magnesium stores: Investigation by simultaneous fluorescent imagings in PC12 cells

Takeshi Kubota, Yutaka Shindo, Kentaro Tokuno, Hirokazu Komatsu, Hiroto Ogawa, Susumu Kudo, Yoshiichiro Kitamura, Koji Suzuki, Kotaro Oka

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77 Citations (Scopus)

Abstract

To determine the nature of intracellular Mg2+ stores and Mg 2+ release mechanisms in differentiated PC12 cells, Mg2+ and Ca2+ mobilizations were measured simultaneously in living cells with KMG-104, a fluorescent Mg2+ indicator, and fura-2, respectively. Treatment with the mitochondrial uncoupler, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), increased both the intracellular Mg2+ concentration ([Mg2+]i) and the [Ca 2+]i in these cells. Possible candidates as intracellular Mg2+ stores under these conditions include intracellular divalent cation binding sites, endoplasmic reticulum (ER), Mg-ATP and mitochondria. Given that no change in [Mg2+]i was induced by caffeine application, intracellular IP3 or Ca2+ liberated by photolysis, it appears that no Mg2+ release mechanism thus exists that is mediated via the action of Ca2+ on membrane-bound receptors in the ER or via the offloading of Mg2+ from binding sites as a result of the increased [Ca2+]i. FCCP treatment for 2 min did not alter the intracellular ATP content, indicating that Mg2+ was not released from Mg-ATP, at least in the first 2 min following exposure to FCCP. FCCP-induced [Mg2+]i increase was observed at mitochondria localized area, and vice versa. These results suggest that the mitochondria serve as the intracellular Mg2+ store in PC12 cell. Simultaneous measurements of [Ca2+]i and mitochondrial membrane potential, and also of [Ca2+]i and [Mg 2+]i, revealed that the initial rise in [Mg 2+]i followed that of mitochondrial depolarization for several seconds. These findings show that the source of Mg2+ in the FCCP-induced [Mg2+]i increase in PC12 cells is mitochondria, and that mitochondrial depolarization triggers the Mg2+ release.

Original languageEnglish
Pages (from-to)19-28
Number of pages10
JournalBiochimica et Biophysica Acta - Molecular Cell Research
Volume1744
Issue number1
DOIs
Publication statusPublished - 2005 May 15

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Keywords

  • FCCP
  • Fluorescent imaging
  • KMG
  • Magnesium
  • Mitochondria
  • Photolysis

ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology
  • Biophysics

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