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Control of mitochondrial motility and distribution by the calcium signal: a homeostatic circuit.

Yi M, Weaver D, Hajnóczky G - J. Cell Biol. (2004)

Bottom Line: By clamping cytoplasmic [Ca2+] ([Ca2+]c) at various levels, mitochondrial motility was found to be regulated by Ca2+ in the physiological range.The inositol 1,4,5-trisphosphate- or ryanodine receptor-mediated [Ca2+]c signal also induced a decrease in mitochondrial motility.This decrease followed the spatial and temporal pattern of the [Ca2+]c signal.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.

ABSTRACT
Mitochondria are dynamic organelles in cells. The control of mitochondrial motility by signaling mechanisms and the significance of rapid changes in motility remains elusive. In cardiac myoblasts, mitochondria were observed close to the microtubular array and displayed both short- and long-range movements along microtubules. By clamping cytoplasmic [Ca2+] ([Ca2+]c) at various levels, mitochondrial motility was found to be regulated by Ca2+ in the physiological range. Maximal movement was obtained at resting [Ca2+]c with complete arrest at 1-2 microM. Movement was fully recovered by returning to resting [Ca2+]c, and inhibition could be repeated with no apparent desensitization. The inositol 1,4,5-trisphosphate- or ryanodine receptor-mediated [Ca2+]c signal also induced a decrease in mitochondrial motility. This decrease followed the spatial and temporal pattern of the [Ca2+]c signal. Diminished mitochondrial motility in the region of the [Ca2+]c rise promotes recruitment of mitochondria to enhance local Ca2+ buffering and energy supply. This mechanism may provide a novel homeostatic circuit in calcium signaling.

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Spatio-temporal pattern of the calcium signal and inhibition of mitochondrial motility. (A) Calcium signal propagation to the mitochondria is not required for the inhibition of motility. Uncoupler (5 μM FCCP and 5 μg/ml Oligo; solid line) or solvent (dashed line) was added to the cells 5 min before stimulation with VP. The uncoupler causes dissipation of the ΔΨm in <1 min and in turn decreases the driving force of the mitochondrial Ca2+ uptake in H9c2 myoblasts (Szalai et al., 2000). Mitochondrial motility showed a slowly developing decrease (red solid line) compared with the control (red dash line). However uncoupler did not prevent the effect of VP on mitochondrial motility, indicating that mitochondrial Ca2+ uptake and ΔΨm were not necessary for the control of motility by the calcium signal. In another set of experiments, the cells were pretreated with uncoupler for 10 min before the recording was started. The inset shows that the residual motility was effectively inhibited by 100 nM VP. Data are the means of nine experiments with uncoupler and four experiments for the control. (B) Reversible and reproducible inhibition of mitochondrial motility by Ca2+. To evaluate the effect of pulsatile increases of [Ca2+]c (black traces) on mitochondrial motility (red traces), the 10 μM of Iono-induced [Ca2+]c elevation was recorded for 10 min (solid lines) or was reversed by addition of 5 mM EGTA and, subsequently, was reestablished by addition of 10 mM CaCl2 (dashed lines). Data are the means of 36 cells from 22 experiments.
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fig3: Spatio-temporal pattern of the calcium signal and inhibition of mitochondrial motility. (A) Calcium signal propagation to the mitochondria is not required for the inhibition of motility. Uncoupler (5 μM FCCP and 5 μg/ml Oligo; solid line) or solvent (dashed line) was added to the cells 5 min before stimulation with VP. The uncoupler causes dissipation of the ΔΨm in <1 min and in turn decreases the driving force of the mitochondrial Ca2+ uptake in H9c2 myoblasts (Szalai et al., 2000). Mitochondrial motility showed a slowly developing decrease (red solid line) compared with the control (red dash line). However uncoupler did not prevent the effect of VP on mitochondrial motility, indicating that mitochondrial Ca2+ uptake and ΔΨm were not necessary for the control of motility by the calcium signal. In another set of experiments, the cells were pretreated with uncoupler for 10 min before the recording was started. The inset shows that the residual motility was effectively inhibited by 100 nM VP. Data are the means of nine experiments with uncoupler and four experiments for the control. (B) Reversible and reproducible inhibition of mitochondrial motility by Ca2+. To evaluate the effect of pulsatile increases of [Ca2+]c (black traces) on mitochondrial motility (red traces), the 10 μM of Iono-induced [Ca2+]c elevation was recorded for 10 min (solid lines) or was reversed by addition of 5 mM EGTA and, subsequently, was reestablished by addition of 10 mM CaCl2 (dashed lines). Data are the means of 36 cells from 22 experiments.

Mentions: The IP3-induced [Ca2+]c signal is propagated to the mitochondria, giving rise to a mitochondrial matrix [Ca2+] ([Ca2+]m) rise that controls the activity of Ca2+-dependent enzymes and ion channels (for review see Duchen, 2000). The primary driving force of the mitochondrial Ca2+ uptake is the ΔΨm that also drives mitochondrial ATP synthesis. To determine whether the [Ca2+]m signal or ΔΨm is necessary for the Ca2+-dependent inhibition of mitochondrial motility, we treated cells with an uncoupler (FCCP added with the ATPase inhibitor, oligomycin to preserve cytosolic ATP; Fig. 3 A). This treatment has been shown to cause rapid dissipation of the ΔΨm (Pacher and Hajnóczky, 2001) and to reduce mitochondrial Ca2+ uptake in H9c2 cells (Szalai et al., 2000). Uncoupler induced a slow attenuation in mitochondrial motility (Fig. 3 A), which may reflect a fall in perimitochondrial ATP that is likely to be needed for movement. However, the VP-induced arrest of mitochondrial movement was preserved in uncoupler-pretreated cells (Fig. 3 A). Thus the [Ca2+]m signal and ΔΨm appears to be dispensable for the Ca2+-mediated inhibition of mitochondrial movement.


Control of mitochondrial motility and distribution by the calcium signal: a homeostatic circuit.

Yi M, Weaver D, Hajnóczky G - J. Cell Biol. (2004)

Spatio-temporal pattern of the calcium signal and inhibition of mitochondrial motility. (A) Calcium signal propagation to the mitochondria is not required for the inhibition of motility. Uncoupler (5 μM FCCP and 5 μg/ml Oligo; solid line) or solvent (dashed line) was added to the cells 5 min before stimulation with VP. The uncoupler causes dissipation of the ΔΨm in <1 min and in turn decreases the driving force of the mitochondrial Ca2+ uptake in H9c2 myoblasts (Szalai et al., 2000). Mitochondrial motility showed a slowly developing decrease (red solid line) compared with the control (red dash line). However uncoupler did not prevent the effect of VP on mitochondrial motility, indicating that mitochondrial Ca2+ uptake and ΔΨm were not necessary for the control of motility by the calcium signal. In another set of experiments, the cells were pretreated with uncoupler for 10 min before the recording was started. The inset shows that the residual motility was effectively inhibited by 100 nM VP. Data are the means of nine experiments with uncoupler and four experiments for the control. (B) Reversible and reproducible inhibition of mitochondrial motility by Ca2+. To evaluate the effect of pulsatile increases of [Ca2+]c (black traces) on mitochondrial motility (red traces), the 10 μM of Iono-induced [Ca2+]c elevation was recorded for 10 min (solid lines) or was reversed by addition of 5 mM EGTA and, subsequently, was reestablished by addition of 10 mM CaCl2 (dashed lines). Data are the means of 36 cells from 22 experiments.
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Related In: Results  -  Collection

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fig3: Spatio-temporal pattern of the calcium signal and inhibition of mitochondrial motility. (A) Calcium signal propagation to the mitochondria is not required for the inhibition of motility. Uncoupler (5 μM FCCP and 5 μg/ml Oligo; solid line) or solvent (dashed line) was added to the cells 5 min before stimulation with VP. The uncoupler causes dissipation of the ΔΨm in <1 min and in turn decreases the driving force of the mitochondrial Ca2+ uptake in H9c2 myoblasts (Szalai et al., 2000). Mitochondrial motility showed a slowly developing decrease (red solid line) compared with the control (red dash line). However uncoupler did not prevent the effect of VP on mitochondrial motility, indicating that mitochondrial Ca2+ uptake and ΔΨm were not necessary for the control of motility by the calcium signal. In another set of experiments, the cells were pretreated with uncoupler for 10 min before the recording was started. The inset shows that the residual motility was effectively inhibited by 100 nM VP. Data are the means of nine experiments with uncoupler and four experiments for the control. (B) Reversible and reproducible inhibition of mitochondrial motility by Ca2+. To evaluate the effect of pulsatile increases of [Ca2+]c (black traces) on mitochondrial motility (red traces), the 10 μM of Iono-induced [Ca2+]c elevation was recorded for 10 min (solid lines) or was reversed by addition of 5 mM EGTA and, subsequently, was reestablished by addition of 10 mM CaCl2 (dashed lines). Data are the means of 36 cells from 22 experiments.
Mentions: The IP3-induced [Ca2+]c signal is propagated to the mitochondria, giving rise to a mitochondrial matrix [Ca2+] ([Ca2+]m) rise that controls the activity of Ca2+-dependent enzymes and ion channels (for review see Duchen, 2000). The primary driving force of the mitochondrial Ca2+ uptake is the ΔΨm that also drives mitochondrial ATP synthesis. To determine whether the [Ca2+]m signal or ΔΨm is necessary for the Ca2+-dependent inhibition of mitochondrial motility, we treated cells with an uncoupler (FCCP added with the ATPase inhibitor, oligomycin to preserve cytosolic ATP; Fig. 3 A). This treatment has been shown to cause rapid dissipation of the ΔΨm (Pacher and Hajnóczky, 2001) and to reduce mitochondrial Ca2+ uptake in H9c2 cells (Szalai et al., 2000). Uncoupler induced a slow attenuation in mitochondrial motility (Fig. 3 A), which may reflect a fall in perimitochondrial ATP that is likely to be needed for movement. However, the VP-induced arrest of mitochondrial movement was preserved in uncoupler-pretreated cells (Fig. 3 A). Thus the [Ca2+]m signal and ΔΨm appears to be dispensable for the Ca2+-mediated inhibition of mitochondrial movement.

Bottom Line: By clamping cytoplasmic [Ca2+] ([Ca2+]c) at various levels, mitochondrial motility was found to be regulated by Ca2+ in the physiological range.The inositol 1,4,5-trisphosphate- or ryanodine receptor-mediated [Ca2+]c signal also induced a decrease in mitochondrial motility.This decrease followed the spatial and temporal pattern of the [Ca2+]c signal.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.

ABSTRACT
Mitochondria are dynamic organelles in cells. The control of mitochondrial motility by signaling mechanisms and the significance of rapid changes in motility remains elusive. In cardiac myoblasts, mitochondria were observed close to the microtubular array and displayed both short- and long-range movements along microtubules. By clamping cytoplasmic [Ca2+] ([Ca2+]c) at various levels, mitochondrial motility was found to be regulated by Ca2+ in the physiological range. Maximal movement was obtained at resting [Ca2+]c with complete arrest at 1-2 microM. Movement was fully recovered by returning to resting [Ca2+]c, and inhibition could be repeated with no apparent desensitization. The inositol 1,4,5-trisphosphate- or ryanodine receptor-mediated [Ca2+]c signal also induced a decrease in mitochondrial motility. This decrease followed the spatial and temporal pattern of the [Ca2+]c signal. Diminished mitochondrial motility in the region of the [Ca2+]c rise promotes recruitment of mitochondria to enhance local Ca2+ buffering and energy supply. This mechanism may provide a novel homeostatic circuit in calcium signaling.

Show MeSH