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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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Spatial relationship between MTs, MFs, and mitochondria. (A) H9c2 cells expressing tubulinGFP and mitoDsRed and incubated in the absence (i) or presence (ii) of 10 μM of an MT-stabilizing agent, taxol. (iii–v) Magnified time-lapse images of a peripheral region of the taxol-pretreated cell. Arrowheads mark the mitochondria that move substantially from the previous image. (vi–ix) Further magnified region showing a single mitochondrion sliding along an MT. (x and xi) A naive and a nocodazole-pretreated cell after permeabilization with digitonin. (B) Inhibition of mitochondrial motility and enhancement of the VP-induced mitochondrial [Ca2+] signal in nocodazole-pretreated cells. (top left) Mitochondrial motility and [Ca2+]c in nocodazole-treated cells (solid lines, 23 cells in 10 measurements) as compared with control cells (dashed lines, 22 cells in 11 measurements). The effect of 100 nM VP is also shown. (top right) Resting [Ca2+]c and the peak value of the VP-induced [Ca2+]c signal in control and nocodazole-pretreated (10 μM for 25–30 min) cells. (bottom) Nuclear matrix and mitochondrial matrix [Ca2+] measured in cells expressing both nuclear and mitochondrial pericam using fast, ratiometric imaging (2 ratio/s). Cells were pretreated with nocodazole (10 μM for 25–30 min) or solvent (control) and stimulated by 100 nM VP. The VP-induced initial [Ca2+]c signal was measured (change in nuclear pericam fluorescent ratio at the first point of the [Ca2+] rise, <25% of the maximal change) and the corresponding change in [Ca2+]m (change in mitochondrial pericam fluorescent ratio) was calculated for each cell (mean ± SEM; n = 16). (C) MFs and mitochondria in H9c2 cells expressing actinGFP and mitoDsRed. Cells were incubated in the absence or presence of 10 μM of nocodazole.
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fig5: Spatial relationship between MTs, MFs, and mitochondria. (A) H9c2 cells expressing tubulinGFP and mitoDsRed and incubated in the absence (i) or presence (ii) of 10 μM of an MT-stabilizing agent, taxol. (iii–v) Magnified time-lapse images of a peripheral region of the taxol-pretreated cell. Arrowheads mark the mitochondria that move substantially from the previous image. (vi–ix) Further magnified region showing a single mitochondrion sliding along an MT. (x and xi) A naive and a nocodazole-pretreated cell after permeabilization with digitonin. (B) Inhibition of mitochondrial motility and enhancement of the VP-induced mitochondrial [Ca2+] signal in nocodazole-pretreated cells. (top left) Mitochondrial motility and [Ca2+]c in nocodazole-treated cells (solid lines, 23 cells in 10 measurements) as compared with control cells (dashed lines, 22 cells in 11 measurements). The effect of 100 nM VP is also shown. (top right) Resting [Ca2+]c and the peak value of the VP-induced [Ca2+]c signal in control and nocodazole-pretreated (10 μM for 25–30 min) cells. (bottom) Nuclear matrix and mitochondrial matrix [Ca2+] measured in cells expressing both nuclear and mitochondrial pericam using fast, ratiometric imaging (2 ratio/s). Cells were pretreated with nocodazole (10 μM for 25–30 min) or solvent (control) and stimulated by 100 nM VP. The VP-induced initial [Ca2+]c signal was measured (change in nuclear pericam fluorescent ratio at the first point of the [Ca2+] rise, <25% of the maximal change) and the corresponding change in [Ca2+]m (change in mitochondrial pericam fluorescent ratio) was calculated for each cell (mean ± SEM; n = 16). (C) MFs and mitochondria in H9c2 cells expressing actinGFP and mitoDsRed. Cells were incubated in the absence or presence of 10 μM of nocodazole.

Mentions: Long-range mitochondrial movements are facilitated by the MTs and certain forms of local movement may use the MFs (Couchman and Rees, 1982; Nangaku et al., 1994; Morris and Hollenbeck, 1995; Varadi et al., 2004). In H9c2 myoblasts expressing tubulinGFP and DsRed targeted to the mitochondria, green fluorescence both marked a complex network of fibers and appeared as a homogeneous signal throughout the cells (Fig. 5 A, i). Labeling of the fibers became more intense, and the homogeneous signal effectively disappeared when the cells were pretreated with taxol, a drug that promotes the polymerization of tubulin (Fig. 5 A, ii). The fibers were retained and the homogeneous signal was promptly eliminated if the cells were permeabilized (Fig. 5 A, x). Based on these data, the fibers represent the MTs and the homogeneous fluorescence is likely to be accounted by monomeric tubulinGFP.


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

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

Spatial relationship between MTs, MFs, and mitochondria. (A) H9c2 cells expressing tubulinGFP and mitoDsRed and incubated in the absence (i) or presence (ii) of 10 μM of an MT-stabilizing agent, taxol. (iii–v) Magnified time-lapse images of a peripheral region of the taxol-pretreated cell. Arrowheads mark the mitochondria that move substantially from the previous image. (vi–ix) Further magnified region showing a single mitochondrion sliding along an MT. (x and xi) A naive and a nocodazole-pretreated cell after permeabilization with digitonin. (B) Inhibition of mitochondrial motility and enhancement of the VP-induced mitochondrial [Ca2+] signal in nocodazole-pretreated cells. (top left) Mitochondrial motility and [Ca2+]c in nocodazole-treated cells (solid lines, 23 cells in 10 measurements) as compared with control cells (dashed lines, 22 cells in 11 measurements). The effect of 100 nM VP is also shown. (top right) Resting [Ca2+]c and the peak value of the VP-induced [Ca2+]c signal in control and nocodazole-pretreated (10 μM for 25–30 min) cells. (bottom) Nuclear matrix and mitochondrial matrix [Ca2+] measured in cells expressing both nuclear and mitochondrial pericam using fast, ratiometric imaging (2 ratio/s). Cells were pretreated with nocodazole (10 μM for 25–30 min) or solvent (control) and stimulated by 100 nM VP. The VP-induced initial [Ca2+]c signal was measured (change in nuclear pericam fluorescent ratio at the first point of the [Ca2+] rise, <25% of the maximal change) and the corresponding change in [Ca2+]m (change in mitochondrial pericam fluorescent ratio) was calculated for each cell (mean ± SEM; n = 16). (C) MFs and mitochondria in H9c2 cells expressing actinGFP and mitoDsRed. Cells were incubated in the absence or presence of 10 μM of nocodazole.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172592&req=5

fig5: Spatial relationship between MTs, MFs, and mitochondria. (A) H9c2 cells expressing tubulinGFP and mitoDsRed and incubated in the absence (i) or presence (ii) of 10 μM of an MT-stabilizing agent, taxol. (iii–v) Magnified time-lapse images of a peripheral region of the taxol-pretreated cell. Arrowheads mark the mitochondria that move substantially from the previous image. (vi–ix) Further magnified region showing a single mitochondrion sliding along an MT. (x and xi) A naive and a nocodazole-pretreated cell after permeabilization with digitonin. (B) Inhibition of mitochondrial motility and enhancement of the VP-induced mitochondrial [Ca2+] signal in nocodazole-pretreated cells. (top left) Mitochondrial motility and [Ca2+]c in nocodazole-treated cells (solid lines, 23 cells in 10 measurements) as compared with control cells (dashed lines, 22 cells in 11 measurements). The effect of 100 nM VP is also shown. (top right) Resting [Ca2+]c and the peak value of the VP-induced [Ca2+]c signal in control and nocodazole-pretreated (10 μM for 25–30 min) cells. (bottom) Nuclear matrix and mitochondrial matrix [Ca2+] measured in cells expressing both nuclear and mitochondrial pericam using fast, ratiometric imaging (2 ratio/s). Cells were pretreated with nocodazole (10 μM for 25–30 min) or solvent (control) and stimulated by 100 nM VP. The VP-induced initial [Ca2+]c signal was measured (change in nuclear pericam fluorescent ratio at the first point of the [Ca2+] rise, <25% of the maximal change) and the corresponding change in [Ca2+]m (change in mitochondrial pericam fluorescent ratio) was calculated for each cell (mean ± SEM; n = 16). (C) MFs and mitochondria in H9c2 cells expressing actinGFP and mitoDsRed. Cells were incubated in the absence or presence of 10 μM of nocodazole.
Mentions: Long-range mitochondrial movements are facilitated by the MTs and certain forms of local movement may use the MFs (Couchman and Rees, 1982; Nangaku et al., 1994; Morris and Hollenbeck, 1995; Varadi et al., 2004). In H9c2 myoblasts expressing tubulinGFP and DsRed targeted to the mitochondria, green fluorescence both marked a complex network of fibers and appeared as a homogeneous signal throughout the cells (Fig. 5 A, i). Labeling of the fibers became more intense, and the homogeneous signal effectively disappeared when the cells were pretreated with taxol, a drug that promotes the polymerization of tubulin (Fig. 5 A, ii). The fibers were retained and the homogeneous signal was promptly eliminated if the cells were permeabilized (Fig. 5 A, x). Based on these data, the fibers represent the MTs and the homogeneous fluorescence is likely to be accounted by monomeric tubulinGFP.

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
Related in: MedlinePlus