Magnesium ion (Mg2+) is one of the essential divalent cations. For example, adenosine triphosphate (ATP) is a universal energy currency in cells, and it is functionally active by binding to Mg2+. Intracellular Mg2+ is, therefore, important as a cofactor and/or modulator of enzymatic activities related to energy metabolism. In facts, dysregulation of Mg2+ homeostasis are involved in various cellular malfunctions and diseases. Recently, we found that main cellular Mg2+ stores are mitochondria, and mitochondria regulate intracellular Mg2+ levels in response to biological signals. In this seminar, I present our techniques of fluorescent imaging for visualizing the mobilization of Mg2+ in cells and also recent findings for Mg2+ function.

Followings are detailed contents.

1) How to visualize the Mg2+ mobilization. For last 20 years, we have developed several types of fluorescent Mg2+ sensors : KMG-201)2), 1043) for visualizing cytosolic Mg2+ concentration ; KMG-1034) for intra-mitochondrial Mg2+ measurement ; KCM-15) for simultaneous imaging for Ca2+ and Mg2+ with single probe ; KMG-104 Ash6) for measuring Mg2+ in specific organelles. We show the features of these Mg 2 + probes compared to those developed previously.

2) Physiological function of Mg2+. We found several physiological stimulus induced mobilization of Mg2+ : Neuronal intracellular Mg2+ increases by stimulation of glutamate7), GABA, depolarization of cell membrane potential8), nitric monoxide (NO)9) and mitochondrial uncoupler FCCP10). Furthermore, application of 1-methyl-4-phenyl-pyridinium ion (MPP+) to PC12 cells (this is a model system for Parkinson’s disease) induces Mg2+ release from mitochondria4) and its molecular mechanisms11). We will also present the relation between the energy metabolism and mitochondrial Mg2+ by using the knock-down of the main mitochondrial Mg2+ transporter Mrs212).

References

1) Suzuki Y et al. Anal Chem. 74(6) : 1423-8 (2002).

2) Kubota T et al. Biochem Biophys Res Commun. 303(1) : 332-6 (2003).

3) Komatsu H et al. J Am Chem Soc. 126(50) : 16353-60 (2004).

4) Shindo Y et al. PLoS One. 6(8) : e23684 (2011).

5) Komatsu H et al. J Am Chem Soc. 127(31) : 10798-9 (2005).

6) Fujii T et al. J Am Chem Soc. 12 ; 136(6) : 2374-81 (2014).

7) Shindo Y et al. J Neurosci Res. 88(14) : 3125-32 (2010).

8) Yamanaka R et al. Neuroscience. 310 : 731-41 (2015).

9) Yamanaka R et al. FEBS Lett. 587(16) : 2643-8 (2013).

10) Kubota T, et al. Biochim Biophys Acta. 1744(1) : 19-28 (2005).

11) Shindo Y et al. Biochim Biophys Acta. 1863(8) : 1979-84 (2016).

12) Yamanaka R et al. Sci Rep.6 : 30027 (2016).

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