Inhibition of mitochondrial calcium uptake rather than efflux impedes calcium release by inositol-1,4,5-trisphosphate-sensitive receptors

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Abstract

Mitochondria modulate cellular Ca2+ signals by accumulating the ion via a uniporter and releasing it via Na+- or H+-exchange. In smooth muscle, inhibition of mitochondrial Ca2+ uptake inhibits Ca2+ release from the sarcoplasmic reticulum (SR) via inositol-1,4,5-trisphosphate-sensitive receptors (IP3R). At least two mechanisms may explain this effect. First, localised uptake of Ca2+ by mitochondria may prevent negative feedback by cytosolic Ca2+ on IP3R activity, or secondly localised provision of Ca2+ by mitochondrial efflux may maintain IP3R function or SR Ca2+ content. To distinguish between these possibilities the role of mitochondrial Ca2+ efflux on IP3R function was examined. IP3 was liberated in freshly isolated single colonic smooth muscle cells and mitochondrial Na+-Ca2+ exchanger inhibited with CGP-37157 (10 μM). Mitochondria accumulated Ca2+ during IP3-evoked [Ca2+]c rises and released the ion back to the cytosol (within 15 s) when mitochondrial Ca2+ efflux was active. When mitochondrial Ca2+ efflux was inhibited by CGP-37157, an extensive and sustained loading of mitochondria with Ca2+ occurred after IP3-evoked Ca2+ release. IP3-evoked [Ca2+]c rises were initially unaffected, then only slowly inhibited by CGP-37157. IP3R activity was required for inhibition to occur; incubation with CGP-37157 for the same duration without IP3 release did not inhibit IP3R. CGP-37157 directly inhibited voltage-gated Ca2+ channel activity, however SR Ca2+ content was unaltered by the drug. Thus, the gradual decline of IP3R function that followed mitochondrial Na+-Ca2+ exchanger inhibition resulted from a gradual overload of mitochondria with Ca2+, leading to a reduced capacity for Ca2+ uptake. Localised uptake of Ca2+ by mitochondria, rather than mitochondrial Ca2+ efflux, appears critical for maintaining IP3R activity.
LanguageEnglish
Pages107-113
Number of pages6
JournalCell Calcium
Volume46
Issue number2
DOIs
Publication statusPublished - 2009

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Inositol 1,4,5-Trisphosphate Receptors
Mitochondria
Calcium
Sarcoplasmic Reticulum
Ions
Cytosol
Smooth Muscle Myocytes
Smooth Muscle
CGP 37157
Pharmaceutical Preparations

Keywords

  • smooth muscle
  • calcium
  • mitochondria
  • IP3R

Cite this

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title = "Inhibition of mitochondrial calcium uptake rather than efflux impedes calcium release by inositol-1,4,5-trisphosphate-sensitive receptors",
abstract = "Mitochondria modulate cellular Ca2+ signals by accumulating the ion via a uniporter and releasing it via Na+- or H+-exchange. In smooth muscle, inhibition of mitochondrial Ca2+ uptake inhibits Ca2+ release from the sarcoplasmic reticulum (SR) via inositol-1,4,5-trisphosphate-sensitive receptors (IP3R). At least two mechanisms may explain this effect. First, localised uptake of Ca2+ by mitochondria may prevent negative feedback by cytosolic Ca2+ on IP3R activity, or secondly localised provision of Ca2+ by mitochondrial efflux may maintain IP3R function or SR Ca2+ content. To distinguish between these possibilities the role of mitochondrial Ca2+ efflux on IP3R function was examined. IP3 was liberated in freshly isolated single colonic smooth muscle cells and mitochondrial Na+-Ca2+ exchanger inhibited with CGP-37157 (10 μM). Mitochondria accumulated Ca2+ during IP3-evoked [Ca2+]c rises and released the ion back to the cytosol (within 15 s) when mitochondrial Ca2+ efflux was active. When mitochondrial Ca2+ efflux was inhibited by CGP-37157, an extensive and sustained loading of mitochondria with Ca2+ occurred after IP3-evoked Ca2+ release. IP3-evoked [Ca2+]c rises were initially unaffected, then only slowly inhibited by CGP-37157. IP3R activity was required for inhibition to occur; incubation with CGP-37157 for the same duration without IP3 release did not inhibit IP3R. CGP-37157 directly inhibited voltage-gated Ca2+ channel activity, however SR Ca2+ content was unaltered by the drug. Thus, the gradual decline of IP3R function that followed mitochondrial Na+-Ca2+ exchanger inhibition resulted from a gradual overload of mitochondria with Ca2+, leading to a reduced capacity for Ca2+ uptake. Localised uptake of Ca2+ by mitochondria, rather than mitochondrial Ca2+ efflux, appears critical for maintaining IP3R activity.",
keywords = "smooth muscle, calcium, mitochondria, IP3R",
author = "S. Chalmers and J.G. McCarron",
year = "2009",
doi = "10.1016/j.ceca.2009.05.007",
language = "English",
volume = "46",
pages = "107--113",
journal = "Cell Calcium",
issn = "0143-4160",
number = "2",

}

TY - JOUR

T1 - Inhibition of mitochondrial calcium uptake rather than efflux impedes calcium release by inositol-1,4,5-trisphosphate-sensitive receptors

AU - Chalmers, S.

AU - McCarron, J.G.

PY - 2009

Y1 - 2009

N2 - Mitochondria modulate cellular Ca2+ signals by accumulating the ion via a uniporter and releasing it via Na+- or H+-exchange. In smooth muscle, inhibition of mitochondrial Ca2+ uptake inhibits Ca2+ release from the sarcoplasmic reticulum (SR) via inositol-1,4,5-trisphosphate-sensitive receptors (IP3R). At least two mechanisms may explain this effect. First, localised uptake of Ca2+ by mitochondria may prevent negative feedback by cytosolic Ca2+ on IP3R activity, or secondly localised provision of Ca2+ by mitochondrial efflux may maintain IP3R function or SR Ca2+ content. To distinguish between these possibilities the role of mitochondrial Ca2+ efflux on IP3R function was examined. IP3 was liberated in freshly isolated single colonic smooth muscle cells and mitochondrial Na+-Ca2+ exchanger inhibited with CGP-37157 (10 μM). Mitochondria accumulated Ca2+ during IP3-evoked [Ca2+]c rises and released the ion back to the cytosol (within 15 s) when mitochondrial Ca2+ efflux was active. When mitochondrial Ca2+ efflux was inhibited by CGP-37157, an extensive and sustained loading of mitochondria with Ca2+ occurred after IP3-evoked Ca2+ release. IP3-evoked [Ca2+]c rises were initially unaffected, then only slowly inhibited by CGP-37157. IP3R activity was required for inhibition to occur; incubation with CGP-37157 for the same duration without IP3 release did not inhibit IP3R. CGP-37157 directly inhibited voltage-gated Ca2+ channel activity, however SR Ca2+ content was unaltered by the drug. Thus, the gradual decline of IP3R function that followed mitochondrial Na+-Ca2+ exchanger inhibition resulted from a gradual overload of mitochondria with Ca2+, leading to a reduced capacity for Ca2+ uptake. Localised uptake of Ca2+ by mitochondria, rather than mitochondrial Ca2+ efflux, appears critical for maintaining IP3R activity.

AB - Mitochondria modulate cellular Ca2+ signals by accumulating the ion via a uniporter and releasing it via Na+- or H+-exchange. In smooth muscle, inhibition of mitochondrial Ca2+ uptake inhibits Ca2+ release from the sarcoplasmic reticulum (SR) via inositol-1,4,5-trisphosphate-sensitive receptors (IP3R). At least two mechanisms may explain this effect. First, localised uptake of Ca2+ by mitochondria may prevent negative feedback by cytosolic Ca2+ on IP3R activity, or secondly localised provision of Ca2+ by mitochondrial efflux may maintain IP3R function or SR Ca2+ content. To distinguish between these possibilities the role of mitochondrial Ca2+ efflux on IP3R function was examined. IP3 was liberated in freshly isolated single colonic smooth muscle cells and mitochondrial Na+-Ca2+ exchanger inhibited with CGP-37157 (10 μM). Mitochondria accumulated Ca2+ during IP3-evoked [Ca2+]c rises and released the ion back to the cytosol (within 15 s) when mitochondrial Ca2+ efflux was active. When mitochondrial Ca2+ efflux was inhibited by CGP-37157, an extensive and sustained loading of mitochondria with Ca2+ occurred after IP3-evoked Ca2+ release. IP3-evoked [Ca2+]c rises were initially unaffected, then only slowly inhibited by CGP-37157. IP3R activity was required for inhibition to occur; incubation with CGP-37157 for the same duration without IP3 release did not inhibit IP3R. CGP-37157 directly inhibited voltage-gated Ca2+ channel activity, however SR Ca2+ content was unaltered by the drug. Thus, the gradual decline of IP3R function that followed mitochondrial Na+-Ca2+ exchanger inhibition resulted from a gradual overload of mitochondria with Ca2+, leading to a reduced capacity for Ca2+ uptake. Localised uptake of Ca2+ by mitochondria, rather than mitochondrial Ca2+ efflux, appears critical for maintaining IP3R activity.

KW - smooth muscle

KW - calcium

KW - mitochondria

KW - IP3R

UR - http://dx.doi.org/10.1016/j.ceca.2009.05.007

U2 - 10.1016/j.ceca.2009.05.007

DO - 10.1016/j.ceca.2009.05.007

M3 - Article

VL - 46

SP - 107

EP - 113

JO - Cell Calcium

T2 - Cell Calcium

JF - Cell Calcium

SN - 0143-4160

IS - 2

ER -