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Three-dimensional electron microscopic reconstruction of intracellular organellar arrangements in vascular smooth muscle--further evidence of nanospaces and contacts.

Tong WC, Sweeney M, Jones CJ, Zhang H, O'Neill SC, Prior I, Taggart MJ - J. Cell. Mol. Med. (2009)

Bottom Line: Here, we turn our attention to vascular smooth muscle and explore the 3-dimensional (3D) ultrastructural positioning of SR found deeper in the cell that is involved in the propagation of Ca(2+) waves.Direct connection of the SR and nuclear membranes is confirmed.Such 3D positioning of centrally located SR further informs us of its likely role in the manifestation of spatiotemporal Ca(2+) dynamics: signal encoding may be facilitated by spatially directed release of Ca(2+) to influence several processes crucial to vascular smooth muscle and resistance artery function including myofilament activation by Ca(2+) waves, mitochondrial respiration and gene transcription.

View Article: PubMed Central - PubMed

Affiliation: Institute of Membrane & Systems Biology, University of Leeds, Leeds, UK.

ABSTRACT
The sarcoplasmic reticulum (SR) of smooth muscle is crucial for appropriate regulation of Ca(2+) signalling. In visceral and vascular smooth muscles the SR is known to periodically lie in close register, within a few nanometres, to the plasma membrane. Recent work has focussed on reconstructions of the ultrastructural arrangement of this so-called peripheral SR that may be important for the genesis of phenomena such as Ca(2+) sparks. Here, we turn our attention to vascular smooth muscle and explore the 3-dimensional (3D) ultrastructural positioning of SR found deeper in the cell that is involved in the propagation of Ca(2+) waves. We use digital reconstruction and volume rendering of serial electron microscopic sections from isolated resistance arteries, pressurized in vitro to mimic cellular geometric conformations anticipated in vivo, to map SR positioning. We confirm that these central portions of SR are in close register with mitochondria and the nucleus with all three organelles tightly enveloped by a myofilament/cytoskeletal lattice. Nanospacings between the SR and individual mitochondria are visible and in three dimensions as the SR contorts to accommodate these organelles. Direct connection of the SR and nuclear membranes is confirmed. Such 3D positioning of centrally located SR further informs us of its likely role in the manifestation of spatiotemporal Ca(2+) dynamics: signal encoding may be facilitated by spatially directed release of Ca(2+) to influence several processes crucial to vascular smooth muscle and resistance artery function including myofilament activation by Ca(2+) waves, mitochondrial respiration and gene transcription.

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Three-dimensional reconstruction of resistance artery smooth muscle SR relationship with mitochondria. A1, longitudinal cross section of resistance artery indicating centrally located SR (stained black, indicated by black arrow) and mitochondria (white arrowhead indicates a mitochondrion) enveloped by myofilament lattice (black asterisks). A2, same section with yellow circle denoting the enlarged portion viewed in A3. B1–B5, consecutive 70-nm-thick sections showing contortions of SR around mitochondria. C1-C5, digitized tracings of SR location from each section appearing cumulatively. D1–D5, cumulative digitized tracings of mitochondrial positioning, in addition to SR, from each section. C6, digitized rendering of SR 3D reconstruction. D6, digitized rendering of mitochondria and SR 3D reconstruction. Scale bars: A1–A2, 2 μm; B1–D6, 300 nm.
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fig01: Three-dimensional reconstruction of resistance artery smooth muscle SR relationship with mitochondria. A1, longitudinal cross section of resistance artery indicating centrally located SR (stained black, indicated by black arrow) and mitochondria (white arrowhead indicates a mitochondrion) enveloped by myofilament lattice (black asterisks). A2, same section with yellow circle denoting the enlarged portion viewed in A3. B1–B5, consecutive 70-nm-thick sections showing contortions of SR around mitochondria. C1-C5, digitized tracings of SR location from each section appearing cumulatively. D1–D5, cumulative digitized tracings of mitochondrial positioning, in addition to SR, from each section. C6, digitized rendering of SR 3D reconstruction. D6, digitized rendering of mitochondria and SR 3D reconstruction. Scale bars: A1–A2, 2 μm; B1–D6, 300 nm.

Mentions: In smooth muscle cells the centrally located SR, mitochondria and nucleus are enshrouded by a myofilament/cytoskeletal filament lattice. Examination of serial sections where the centrally located mitochondria were visible showed that the black stained, electron dense SR is in close proximity to individual mitochondria (Fig. 1). Digital 3D reconstruction of these serial sections followed by volume rendering results in the visualization of SR contortions between and around the mitochondria (Fig. 1 and Supporting Information Files S1 and S2 [‘render_SR’ and ‘render_SR_mito’]).


Three-dimensional electron microscopic reconstruction of intracellular organellar arrangements in vascular smooth muscle--further evidence of nanospaces and contacts.

Tong WC, Sweeney M, Jones CJ, Zhang H, O'Neill SC, Prior I, Taggart MJ - J. Cell. Mol. Med. (2009)

Three-dimensional reconstruction of resistance artery smooth muscle SR relationship with mitochondria. A1, longitudinal cross section of resistance artery indicating centrally located SR (stained black, indicated by black arrow) and mitochondria (white arrowhead indicates a mitochondrion) enveloped by myofilament lattice (black asterisks). A2, same section with yellow circle denoting the enlarged portion viewed in A3. B1–B5, consecutive 70-nm-thick sections showing contortions of SR around mitochondria. C1-C5, digitized tracings of SR location from each section appearing cumulatively. D1–D5, cumulative digitized tracings of mitochondrial positioning, in addition to SR, from each section. C6, digitized rendering of SR 3D reconstruction. D6, digitized rendering of mitochondria and SR 3D reconstruction. Scale bars: A1–A2, 2 μm; B1–D6, 300 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3823414&req=5

fig01: Three-dimensional reconstruction of resistance artery smooth muscle SR relationship with mitochondria. A1, longitudinal cross section of resistance artery indicating centrally located SR (stained black, indicated by black arrow) and mitochondria (white arrowhead indicates a mitochondrion) enveloped by myofilament lattice (black asterisks). A2, same section with yellow circle denoting the enlarged portion viewed in A3. B1–B5, consecutive 70-nm-thick sections showing contortions of SR around mitochondria. C1-C5, digitized tracings of SR location from each section appearing cumulatively. D1–D5, cumulative digitized tracings of mitochondrial positioning, in addition to SR, from each section. C6, digitized rendering of SR 3D reconstruction. D6, digitized rendering of mitochondria and SR 3D reconstruction. Scale bars: A1–A2, 2 μm; B1–D6, 300 nm.
Mentions: In smooth muscle cells the centrally located SR, mitochondria and nucleus are enshrouded by a myofilament/cytoskeletal filament lattice. Examination of serial sections where the centrally located mitochondria were visible showed that the black stained, electron dense SR is in close proximity to individual mitochondria (Fig. 1). Digital 3D reconstruction of these serial sections followed by volume rendering results in the visualization of SR contortions between and around the mitochondria (Fig. 1 and Supporting Information Files S1 and S2 [‘render_SR’ and ‘render_SR_mito’]).

Bottom Line: Here, we turn our attention to vascular smooth muscle and explore the 3-dimensional (3D) ultrastructural positioning of SR found deeper in the cell that is involved in the propagation of Ca(2+) waves.Direct connection of the SR and nuclear membranes is confirmed.Such 3D positioning of centrally located SR further informs us of its likely role in the manifestation of spatiotemporal Ca(2+) dynamics: signal encoding may be facilitated by spatially directed release of Ca(2+) to influence several processes crucial to vascular smooth muscle and resistance artery function including myofilament activation by Ca(2+) waves, mitochondrial respiration and gene transcription.

View Article: PubMed Central - PubMed

Affiliation: Institute of Membrane & Systems Biology, University of Leeds, Leeds, UK.

ABSTRACT
The sarcoplasmic reticulum (SR) of smooth muscle is crucial for appropriate regulation of Ca(2+) signalling. In visceral and vascular smooth muscles the SR is known to periodically lie in close register, within a few nanometres, to the plasma membrane. Recent work has focussed on reconstructions of the ultrastructural arrangement of this so-called peripheral SR that may be important for the genesis of phenomena such as Ca(2+) sparks. Here, we turn our attention to vascular smooth muscle and explore the 3-dimensional (3D) ultrastructural positioning of SR found deeper in the cell that is involved in the propagation of Ca(2+) waves. We use digital reconstruction and volume rendering of serial electron microscopic sections from isolated resistance arteries, pressurized in vitro to mimic cellular geometric conformations anticipated in vivo, to map SR positioning. We confirm that these central portions of SR are in close register with mitochondria and the nucleus with all three organelles tightly enveloped by a myofilament/cytoskeletal lattice. Nanospacings between the SR and individual mitochondria are visible and in three dimensions as the SR contorts to accommodate these organelles. Direct connection of the SR and nuclear membranes is confirmed. Such 3D positioning of centrally located SR further informs us of its likely role in the manifestation of spatiotemporal Ca(2+) dynamics: signal encoding may be facilitated by spatially directed release of Ca(2+) to influence several processes crucial to vascular smooth muscle and resistance artery function including myofilament activation by Ca(2+) waves, mitochondrial respiration and gene transcription.

Show MeSH