Mitochondrial transport of K+ and Mg2+

Diwan, Joyce Johnson

doi:10.1016/s0304-4173(87)80001-0

Cited by 37 publications

(11 citation statements)

References 120 publications

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“…An intracellular organelle capable of storing large amounts of magnesium is the mitochondrion, and magnesium is involved in a number of enzymatic processes that are confined to mitochondria (36,37). To test whether mitochondria represent the critical magnesium stores responsible for the uptake of cytosolic magnesium, we interfered with the mitochondrial metabolism in various ways.…”

Section: Resultsmentioning

confidence: 99%

Calcium‐magnesium interactions in pancreatic acinar cells

Mooren¹,

Turi²,

Günzel

et al. 2001

FASEB j.

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Although the role of calcium (Ca2+) in the signal transduction and pathobiology of the exocrine pancreas is firmly established, the role of magnesium (Mg2+) remains unclear. We have characterized the intracellular distribution of Mg2+ in response to hormone stimulation in isolated mouse pancreatic acinar cells and studied the role of Mg2+ in modulating Ca2+ signaling using microspectrofluorometry and digital imaging of Ca2+- or Mg2+-sensitive fluorescent dyes as well as Mg2+-sensitive intracellular microelectrodes. Our results indicate that an increase in intracellular Mg2+ concentrations reduced the cholecystokinin (CCK) -induced Ca2+ oscillations by inhibiting the capacitive Ca2+ influx. An intracellular Ca2+ mobilization, on the other hand, was paralleled by a decrease in [Mg2+]i, which was reversible upon hormone withdrawal independent of the electrochemical gradients for Mg2+, Ca2+, Na+, and K+, and not caused by Mg2+ efflux from acinar cells. In an attempt to characterize possible Mg2+ stores that would explain the reversible, hormone-induced intracellular Mg2+ movements, we ruled out mitochondria or ATP as potential Mg2+ buffers and found that the CCK-induced [Mg2+]i decrease was initiated at the basolateral part of the acinar cells, where most of the endoplasmic reticulum (ER) is located, and progressed from there toward the apical pole of the acinar cells in an antiparallel fashion to Ca2+ waves. These experiments represent the first characterization of intracellular Mg2+ movements in the exocrine pancreas, provide evidence for possible Mg2+ stores in the ER, and indicate that the spatial and temporal distribution of intracellular Mg concentrations profoundly affects acinar cell Ca2+ signaling.

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Section: Resultsmentioning

confidence: 99%

Calcium‐magnesium interactions in pancreatic acinar cells

Mooren¹,

Turi²,

Günzel

et al. 2001

FASEB j.

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“…As far as the influx of Mg 2+ into mammalian mitochondria had been studied by the use of either 28 Mg 2+ or Mg 2+ ‐sensitive fluorescent dyes, the responses of [Mg 2+ ] m to [Mg 2+ ] e were comparatively small and less immediate than seen here (Diwan et al ., 1979; Diwan, 1987; Rutter et al ., 1990; Jung et al ., 1997). Limitations in the determination of ion fluxes and the lack of a specific inhibitor, or of mutants affecting Mg 2+ fluxes, previously made it difficult to resolve the question of a specific mitochondrial Mg 2+ influx system.…”

Section: Discussionmentioning

confidence: 99%

“…Flux studies with 28 Mg 2+ revealed the presence of a concentration‐dependent and saturable Mg 2+ influx mechanism (Diwan et al ., 1979; Diwan, 1987). Jung et al .…”

Section: Introductionmentioning

confidence: 99%

Mrs2p is an essential component of the major electrophoretic Mg2+ influx system in mitochondria

Kolísek¹

2003

The EMBO Journal

197

224

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Steady-state concentrations of mitochondrial Mg 2+ previously have been shown to vary with the expression of Mrs2p, a component of the inner mitochondrial membrane with two transmembrane domains. While its structural and functional similarity to the bacterial Mg 2+ transport protein CorA suggested a role for Mrs2p in Mg 2+ in¯ux into the organelle, other functions in cation homeostasis could not be excluded. Making use of the¯uorescent dye mag-fura 2 to measure free Mg 2+ concentrations continuously, we describe here a high capacity, rapid Mg 2+ in¯ux system in isolated yeast mitochondria, driven by the mitochondrial membrane potential Dy and inhibited by cobalt(III)hexaammine. Overexpression of Mrs2p increases in¯ux rates 5-fold, while the deletion of the MRS2 gene abolishes this high capacity Mg 2+ in¯ux. Mg 2+ ef¯ux from isolated mitochondria, observed with low Dy only, also requires the presence of Mrs2p. Cross-linking experiments revealed the presence of Mrs2p-containing complexes in the mitochondrial membrane, probably constituting Mrs2p homooligomers. Taken together, these ®ndings characterize Mrs2p as the ®rst molecularly identi®ed metal ion channel protein in the inner mitochondrial membrane.

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“…This cation is involved in the regulation of mitochondrial volume and of enzyme activities associated with these organelles [2]. Since ä + is significant for mitochondrial functioning, the mechanisms of K + transport attract close attention for a long time already [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Functional identification of ATP-sensitive K+ uniporter in mitochondria from sugar beet taproot

Шугаев

Andreev

Vyskrebentseva

2005

Russ J Plant Physiol

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Mitochondria isolated from sugar beet ( Beta vulgaris L.) taproot were shown to swell spontaneously after the transfer from a sucrose-containing isolation medium to isoosmotic potassium chloride solutions. The kinetics of this process was strongly retarded after the replacement of potassium with sodium in the incubation medium and was substantially stimulated by the electron-transport chain activity and valinomycin. At neutral pH of the incubation medium, the rate of K + -dependent swelling of mitochondria decreased by 30-50% after adding 1 mM ATP but was insensitive to other nucleotides (GTP, UTP, and CTP). In the medium acidified to pH 6.0, the addition of ATP caused shrinkage of mitochondria that had been swollen in the KCl medium. In the absence of this nucleotide, the kinetics of K + -dependent swelling of mitochondria was considerably decelerated upon the acidification of the incubation medium. The effects of ATP were independent of the presence or absence of oligomycin and atractyloside. However, the ATP-dependent shrinkage of mitochondria was inhibited in the presence of quinine, and this agent also inhibited K + -dependent swelling of organelles in potassium acetate solutions. The presence of K + ions in the incubation medium caused a rapid dissipation of the mitochondrial membrane potential ( ∆ψ ) that was generated during succinate oxidation. The addition of ATP to the reaction medium resulted in the oligomycin-insensitive restoration of ∆ψ . The results are regarded as evidence that the membrane of taproot mitochondria is endowed with functionally active ATP-sensitive K + uniporter. This system is likely to represent a K + channel that catalyzes the electrogenic transfer of potassium ions to the mitochondrial matrix. It is supposed that the membrane of taproot mitochondria also contains a quinine-sensitive K + /H + antiporter that catalyzes the efflux of potassium from the matrix or, on the contrary, the accumulation of K + in the presence of potassium acetate.

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Mitochondrial transport of K+ and Mg2+

Cited by 37 publications

References 120 publications

Calcium‐magnesium interactions in pancreatic acinar cells

Calcium‐magnesium interactions in pancreatic acinar cells

Mrs2p is an essential component of the major electrophoretic Mg2+ influx system in mitochondria

Functional identification of ATP-sensitive K+ uniporter in mitochondria from sugar beet taproot

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