Quantification of Mg2+ extrusion and cytosolic Mg2+-buffering in Xenopus oocytes

Gabriel, Thomas; Günzel, Dorothee

doi:10.1016/j.abb.2006.07.007

Cited by 18 publications

(16 citation statements)

References 38 publications

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“…Once the microelectrodes were inside the cell, that is isolated from the extracellular buffer solution, an electrochemical potential difference signal was detected identifying the activity of Mg 2+ . The measured intracellular Mg 2+ concentration for human adipocytes was 0.4 to 0.5 mM and for frog oocyte it was 0.8 to 0.9 mM, closely consistent with the intracellular concentration reported in the literature (Nadler and Scott, 1994;Gabriel and Gunzel, 2007;Vemana et al, 2008;Lyashchenko and Tibbs, 2008).…”

Section: Measurements Of Intracellular Free Mg 2+ Concentrationssupporting

confidence: 76%

Functionalized ZnO nanorod-based selective magnesium ion sensor for intracellular measurements

Asif¹,

Ali²,

Nur³

et al. 2010

Biosensors and Bioelectronics

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Section: Measurements Of Intracellular Free Mg 2+ Concentrationssupporting

confidence: 76%

Functionalized ZnO nanorod-based selective magnesium ion sensor for intracellular measurements

Asif¹,

Ali²,

Nur³

et al. 2010

Biosensors and Bioelectronics

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“…Some of them alter their expression levels or localization based on the environmental Mg 2+ concentration. Buffering and muffling of increased [Mg 2+ ] cyto are carried out mainly by Mg 2+ extrusion via the Na + /Mg 2+ exchanger and Mg 2+ binding to ATP [38]. In PC12 cells, Mg 2+ is extruded via the Na + /Mg 2+ exchanger after FCCP administration [17].…”

Section: Resultsmentioning

confidence: 99%

“…This antiporter electroneutrally mediates Mg 2+ transport depending on the concentration gradients of P i and ATP [23]. The ATP concentration also affects the Mg 2+ concentration [38]. Moreover, it was reported that unidentified Mg 2+ –binding proteins exist in the intermembrane space of mitochondria [42].…”

Section: Resultsmentioning

confidence: 99%

Newly Developed Mg2+–Selective Fluorescent Probe Enables Visualization of Mg2+ Dynamics in Mitochondria

et al. 2011

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Mg2+ plays important roles in numerous cellular functions. Mitochondria take part in intracellular Mg2+ regulation and the Mg2+ concentration in mitochondria affects the synthesis of ATP. However, there are few methods to observe Mg2+ in mitochondria in intact cells. Here, we have developed a novel Mg2+–selective fluorescent probe, KMG-301, that is functional in mitochondria. This probe changes its fluorescence properties solely depending on the Mg2+ concentration in mitochondria under physiologically normal conditions. Simultaneous measurements using this probe together with a probe for cytosolic Mg2+, KMG-104, enabled us to compare the dynamics of Mg2+ in the cytosol and in mitochondria. With this method, carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP)–induced Mg2+ mobilization from mitochondria to the cytosol was visualized. Although a FCCP–induced decrease in the Mg2+ concentration in mitochondria and an increase in the cytosol were observed both in differentiated PC12 cells and in hippocampal neurons, the time-courses of concentration changes varied with cell type. Moreover, the relationship between mitochondrial Mg2+ and Parkinson's disease was analyzed in a cellular model of Parkinson's disease by using the 1-methyl-4-phenylpyridinium ion (MPP+). A gradual decrease in the Mg2+ concentration in mitochondria was observed in response to MPP+ in differentiated PC12 cells. These results indicate that KMG-301 is useful for investigating Mg2+ dynamics in mitochondria. All animal procedures to obtain neurons from Wistar rats were approved by the ethical committee of Keio University (permit number is 09106-(1)).

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“…First, an increase in the IOPC current at extreme positive potentials is not observed in the whole cell current. Second, the extent of rectification observed in TEVC is only quantitatively reproduced in IOPC when the free Mg concentration is increased to ∼1.9 mM while the bulk free concentration in an oocyte is estimated to be closer to 0.3 mM (Gabriel and Gunzel, 2007). These observations suggest that either block by other polyvalent cations contributes to the shape of the whole cell current or the action of Mg is modified in the context of an intact cell.…”

Section: Resultsmentioning

confidence: 99%

Ion binding in the Open HCN Pacemaker Channel Pore: Fast Mechanisms to Shape “Slow” Channels

Lyashchenko¹,

Tibbs

2008

The Journal of General Physiology

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IH pacemaker channels carry a mixed monovalent cation current that, under physiological ion gradients, reverses at ∼−34 mV, reflecting a 4:1 selectivity for K over Na. However, IH channels display anomalous behavior with respect to permeant ions such that (a) open channels do not exhibit the outward rectification anticipated assuming independence; (b) gating and selectivity are sensitive to the identity and concentrations of externally presented permeant ions; (c) the channels' ability to carry an inward Na current requires the presence of external K even though K is a minor charge carrier at negative voltages. Here we show that open HCN channels (the hyperpolarization-activated, cyclic nucleotide sensitive pore forming subunits of IH) undergo a fast, voltage-dependent block by intracellular Mg in a manner that suggests the ion binds close to, or within, the selectivity filter. Eliminating internal divalent ion block reveals that (a) the K dependence of conduction is mediated via K occupancy of site(s) within the pore and that asymmetrical occupancy and/or coupling of these sites to flux further shapes ion flow, and (b) the kinetics of equilibration between K-vacant and K-occupied states of the pore (10–20 μs or faster) is close to the ion transit time when the pore is occupied by K alone (∼0.5–3 μs), a finding that indicates that either ion:ion repulsion involving Na is adequate to support flux (albeit at a rate below our detection threshold) and/or the pore undergoes rapid, permeant ion-sensitive equilibration between nonconducting and conducting configurations. Biophysically, further exploration of the Mg site and of interactions of Na and K within the pore will tell us much about the architecture and operation of this unusual pore. Physiologically, these results suggest ways in which “slow” pacemaker channels may contribute dynamically to the shaping of fast processes such as Na-K or Ca action potentials.

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Quantification of Mg2+ extrusion and cytosolic Mg2+-buffering in Xenopus oocytes

Cited by 18 publications

References 38 publications

Functionalized ZnO nanorod-based selective magnesium ion sensor for intracellular measurements

Functionalized ZnO nanorod-based selective magnesium ion sensor for intracellular measurements

Newly Developed Mg2+–Selective Fluorescent Probe Enables Visualization of Mg2+ Dynamics in Mitochondria

Ion binding in the Open HCN Pacemaker Channel Pore: Fast Mechanisms to Shape “Slow” Channels

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