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Dissection of Mitochondrial Ca2+ Uptake and Release Fluxes in Situ after Depolarization-Evoked [Ca2+]i Elevations in Sympathetic Neurons

By Stephen L. Colegrove, Meredith A. Albrecht and David D. Friel

Abstract

We studied how mitochondrial Ca2+ transport influences [Ca2+]i dynamics in sympathetic neurons. Cells were treated with thapsigargin to inhibit Ca2+ accumulation by SERCA pumps and depolarized to elevate [Ca2+]i; the recovery that followed repolarization was then examined. The total Ca2+ flux responsible for the [Ca2+]i recovery was separated into mitochondrial and nonmitochondrial components based on sensitivity to the proton ionophore FCCP, a selective inhibitor of mitochondrial Ca2+ transport in these cells. The nonmitochondrial flux, representing net Ca2+ extrusion across the plasma membrane, has a simple dependence on [Ca2+]i, while the net mitochondrial flux (Jmito) is biphasic, indicative of Ca2+ accumulation during the initial phase of recovery when [Ca2+]i is high, and net Ca2+ release during later phases of recovery. During each phase, mitochondrial Ca2+ transport has distinct effects on recovery kinetics. Jmito was separated into components representing mitochondrial Ca2+ uptake and release based on sensitivity to the specific mitochondrial Na+/Ca2+ exchange inhibitor, CGP 37157 (CGP). The CGP-resistant (uptake) component of Jmito increases steeply with [Ca2+]i, as expected for transport by the mitochondrial uniporter. The CGP-sensitive (release) component is inhibited by lowering the intracellular Na+ concentration and depends on both intra- and extramitochondrial Ca2+ concentration, as expected for the Na+/Ca2+ exchanger. Above ∼400 nM [Ca2+]i, net mitochondrial Ca2+ transport is dominated by uptake and is largely insensitive to CGP. When [Ca2+]i is ∼200–300 nM, the net mitochondrial flux is small but represents the sum of much larger uptake and release fluxes that largely cancel. Thus, mitochondrial Ca2+ transport occurs in situ at much lower concentrations than previously thought, and may provide a mechanism for quantitative control of ATP production after brief or low frequency stimuli that raise [Ca2+]i to levels below ∼500 nM

Topics: Original Article
Publisher: The Rockefeller University Press
OAI identifier: oai:pubmedcentral.nih.gov:2217215
Provided by: PubMed Central
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    1. (1992). A caffeine- and ryanodine-sensitive Ca21 store in bullfrog sympathetic neurones modulates effects of Ca21 entry on [Ca21]i.
    2. (1985). A new generation of Ca21 indicators with greatly improved fluorescence properties.
    3. (1996). A reevaluation of the role of mitochondria in neuronal Ca21 homeostasis.
    4. (1993). A role for the mitochondrial Na1-Ca21 exchanger in the regulation of oxidative phosphorylation in isolated heart mitochondria.
    5. (1997). Action potential-dependent regulation of gene expression: temporal specificity in Ca21, cAMP-responsive element binding proteins, and mitogenactivated protein kinase signaling.
    6. (1994). An FCCP-sensitive Ca21 store in bullfrog sympathetic neurons and its participation in stimulusevoked changes in [Ca21]i.
    7. (1992). Calcium gradients and buffers in bovine chromaffin cells.
    8. (1994). Calcium homeostasis in identified rat gonadotrophs.
    9. (1997). CGP 37157 modulates mitochondrial Ca21 homeostasis in cultured rat dorsal root ganglion neurons.
    10. (1993). Characteristics of Ca21 release induced by Ca21 influx in cultured bullfrog sympathetic neurons.
    11. (1998). Close contacts with the endoplasmic reticulum as determinants of mitochondrial Ca21 responses.
    12. (1999). Contributions of mitochondria to animal physiology: from homeostatic sensor to calcium signaling and cell death.
    13. (1990). Cytoplasmic [Ca21]i in mammalian ventricle: dynamic control by cellular processes.
    14. (1997). cytosol of adrenal chromaffin cells.
    15. (1998). Cytosolic and mitochondrial Ca21 signals in patch clamped mammalian ventricular myocytes.
    16. (1995). Decoding of cytosolic calcium oscillations in the mitochondria.
    17. (1999). Depolarization-induced mitochondrial Ca accumulation in sympathetic neurons: spatial and temporal characteristics.
    18. (1996). Dominant role of mitochondria in clearance of large Ca21 loads from rat adrenal chromaffin cells.
    19. (1998). Effects of mitochondrion on calcium transients in intact presynaptic terminals depend on frequency of nerve firing.
    20. (1982). Evidence for the existence of regulatory sites for Ca21 on the Na1/Ca21 carrier of cardiac mitochondria.
    21. (1998). Evidence that mitochondria buffer physiological Ca21 loads in lizard motor nerve terminals.
    22. (1984). Glucagon effects on the membrane potential and calcium uptake rate of rat liver mitochondria.
    23. (1998). Integrating cytosolic calcium signals into mitochondrial metabolic responses.
    24. (1998). Intracellular calcium clearance in Purkinje cell somata from rat cerebellar slices.
    25. (1971). Introduction to Mathematical Statistics. 4th edition.
    26. (1986). Kinetics of mitochondrial calcium transport.
    27. (1990). Mechanisms by which mitochondria transport calcium.
    28. (1973). Mechanisms for intracellular calcium regulation in heart.
    29. (1997). Mitochondria accumulate Ca21 following intense glutamate stimulation of cultured rat forebrain neurons.
    30. (1995). Mitochondria and Na1/Ca21 exchange buffer glutamate-induced calcium loads in cultured cortical neurons.
    31. (1978). Mitochondria and other calcium buffers of squid axon studied in situ.
    32. (1994). Mitochondria buffer physiological calcium loads in cultured rat dorsal root ganglion neurons.
    33. (1998). Mitochondria—the Kraken wakes! Trends Neurosci.
    34. (1993). Mitochondrial Ca21 transport and the role of intramitochondrial Ca21 in the regulation of energy metabolism.
    35. (1982). Mitochondrial calcium transport.
    36. (1997). Mitochondrial involvement in posttetantic potentiation of synaptic transmission.
    37. (1998). Mitochondrial oversight of cellular Ca21 signaling.
    38. (1997). Mitochondrial regulation of store-operated calcium signaling in T Lymphocytes.
    39. (1998). Oxygen-bridged dinuclear ruthenium amine complex specifically inhibits Ca21 uptake into mitochondria in vitro and in situ in single cardiac myocytes.
    40. (1990). Regulation of the intracellular free calcium concentration in single rat dorsal root ganglion neurones in vitro.
    41. (1993). Selectivity of inhibition of Na1 -Ca21 exchange of heart mitochondrial by benzothiazepine CGP-37157.
    42. (1988). Structural dependency of the inhibitory action of benzodiazepines and reD Ca [] m t () viki T vm ¤ () J t mito t¢. d
    43. (1990). Subcellular calcium transients visualized by confocal microscopy in a voltageclamped vertebrate neuron.
    44. (1979). The calcium cycle of mitochondria.
    45. (1978). The interrelations between the transport of sodium and calcium in mitochondria of various mammalian tissues.
    46. (1998). The mitochondrial Na1/ Ca21 exchanger and its role in depolarization-induced [Ca21]i responses in sympathetic neurons.
    47. (1996). The temporal profile of calcium transients in voltage clamped gastric myocytes from Bufo marinus.
    48. (1994). Transport of calcium by mitochondria.

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