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ATP- and gap junction-dependent intercellular calcium signaling in osteoblastic cells.

Jorgensen NR, Geist ST, Civitelli R, Steinberg TH - J. Cell Biol. (1997)

Bottom Line: ROS 17/2.8 cells, which express the gap junction protein connexin43 (Cx43), are well dye coupled, and lack P2U receptors, transmitted slow gap junction-dependent calcium waves that did not require release of intracellular calcium stores.These studies demonstrate that activation of P2U purinergic receptors can propagate intercellular calcium, and describe a novel Cx43-dependent mechanism for calcium wave propagation that does not require release of intracellular calcium stores by IP3.These studies suggest that gap junction communication mediated by either Cx43 or Cx45 does not allow passage of IP3 well enough to elicit release of intracellular calcium stores in neighboring cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Many cells coordinate their activities by transmitting rises in intracellular calcium from cell to cell. In nonexcitable cells, there are currently two models for intercellular calcium wave propagation, both of which involve release of inositol trisphosphate (IP3)- sensitive intracellular calcium stores. In one model, IP3 traverses gap junctions and initiates the release of intracellular calcium stores in neighboring cells. Alternatively, calcium waves may be mediated not by gap junctional communication, but rather by autocrine activity of secreted ATP on P2 purinergic receptors. We studied mechanically induced calcium waves in two rat osteosarcoma cell lines that differ in the gap junction proteins they express, in their ability to pass microinjected dye from cell to cell, and in their expression of P2Y2 (P2U) purinergic receptors. ROS 17/2.8 cells, which express the gap junction protein connexin43 (Cx43), are well dye coupled, and lack P2U receptors, transmitted slow gap junction-dependent calcium waves that did not require release of intracellular calcium stores. UMR 106-01 cells predominantly express the gap junction protein connexin 45 (Cx45), are poorly dye coupled, and express P2U receptors; they propagated fast calcium waves that required release of intracellular calcium stores and activation of P2U purinergic receptors, but not gap junctional communication. ROS/P2U transfectants and UMR/Cx43 transfectants expressed both types of calcium waves. Gap junction-independent, ATP-dependent intercellular calcium waves were also seen in hamster tracheal epithelia cells. These studies demonstrate that activation of P2U purinergic receptors can propagate intercellular calcium, and describe a novel Cx43-dependent mechanism for calcium wave propagation that does not require release of intracellular calcium stores by IP3. These studies suggest that gap junction communication mediated by either Cx43 or Cx45 does not allow passage of IP3 well enough to elicit release of intracellular calcium stores in neighboring cells.

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Calcium waves are propagated among islands of UMR  cells. Calcium waves were induced in a subconfluent monolayer  of fluo-3–loaded UMR cells. The outline of cells in the field of  view is shown in the upper left panel. A cell in the middle of the  cell island was stimulated, and images were taken at intervals.  Cells that propagated the calcium wave but were not in physical  contact with the stimulated cell are indicated by arrows. Time after  stimulation in s is shown on each panel.
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Figure 6: Calcium waves are propagated among islands of UMR cells. Calcium waves were induced in a subconfluent monolayer of fluo-3–loaded UMR cells. The outline of cells in the field of view is shown in the upper left panel. A cell in the middle of the cell island was stimulated, and images were taken at intervals. Cells that propagated the calcium wave but were not in physical contact with the stimulated cell are indicated by arrows. Time after stimulation in s is shown on each panel.

Mentions: To confirm that calcium waves in UMR cells occur independently of gap junctional communication, we performed experiments using subconfluent cultures in which independent islands of cells could be observed. These islands of cells were not in physical contact as assessed by phase microscopy. We then induced intercellular calcium waves by mechanical stimulation in single cells within these monolayers. Stimulation of single UMR cells resulted in the rapid spread of a calcium wave to all the cells within the small cell islands. In addition, the calcium wave spread with a short time lag to cells in nearby cell islands that were not in physical contact with the stimulated cell (Fig. 6). When we performed similar experiments in cultures of ROS cells, spread of calcium waves between islands of cells was never observed. These experiments confirm that gap junctional communication is not required for UMR calcium waves, and are consistent with a role for gap junctional communication in ROS calcium waves.


ATP- and gap junction-dependent intercellular calcium signaling in osteoblastic cells.

Jorgensen NR, Geist ST, Civitelli R, Steinberg TH - J. Cell Biol. (1997)

Calcium waves are propagated among islands of UMR  cells. Calcium waves were induced in a subconfluent monolayer  of fluo-3–loaded UMR cells. The outline of cells in the field of  view is shown in the upper left panel. A cell in the middle of the  cell island was stimulated, and images were taken at intervals.  Cells that propagated the calcium wave but were not in physical  contact with the stimulated cell are indicated by arrows. Time after  stimulation in s is shown on each panel.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139805&req=5

Figure 6: Calcium waves are propagated among islands of UMR cells. Calcium waves were induced in a subconfluent monolayer of fluo-3–loaded UMR cells. The outline of cells in the field of view is shown in the upper left panel. A cell in the middle of the cell island was stimulated, and images were taken at intervals. Cells that propagated the calcium wave but were not in physical contact with the stimulated cell are indicated by arrows. Time after stimulation in s is shown on each panel.
Mentions: To confirm that calcium waves in UMR cells occur independently of gap junctional communication, we performed experiments using subconfluent cultures in which independent islands of cells could be observed. These islands of cells were not in physical contact as assessed by phase microscopy. We then induced intercellular calcium waves by mechanical stimulation in single cells within these monolayers. Stimulation of single UMR cells resulted in the rapid spread of a calcium wave to all the cells within the small cell islands. In addition, the calcium wave spread with a short time lag to cells in nearby cell islands that were not in physical contact with the stimulated cell (Fig. 6). When we performed similar experiments in cultures of ROS cells, spread of calcium waves between islands of cells was never observed. These experiments confirm that gap junctional communication is not required for UMR calcium waves, and are consistent with a role for gap junctional communication in ROS calcium waves.

Bottom Line: ROS 17/2.8 cells, which express the gap junction protein connexin43 (Cx43), are well dye coupled, and lack P2U receptors, transmitted slow gap junction-dependent calcium waves that did not require release of intracellular calcium stores.These studies demonstrate that activation of P2U purinergic receptors can propagate intercellular calcium, and describe a novel Cx43-dependent mechanism for calcium wave propagation that does not require release of intracellular calcium stores by IP3.These studies suggest that gap junction communication mediated by either Cx43 or Cx45 does not allow passage of IP3 well enough to elicit release of intracellular calcium stores in neighboring cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.

ABSTRACT
Many cells coordinate their activities by transmitting rises in intracellular calcium from cell to cell. In nonexcitable cells, there are currently two models for intercellular calcium wave propagation, both of which involve release of inositol trisphosphate (IP3)- sensitive intracellular calcium stores. In one model, IP3 traverses gap junctions and initiates the release of intracellular calcium stores in neighboring cells. Alternatively, calcium waves may be mediated not by gap junctional communication, but rather by autocrine activity of secreted ATP on P2 purinergic receptors. We studied mechanically induced calcium waves in two rat osteosarcoma cell lines that differ in the gap junction proteins they express, in their ability to pass microinjected dye from cell to cell, and in their expression of P2Y2 (P2U) purinergic receptors. ROS 17/2.8 cells, which express the gap junction protein connexin43 (Cx43), are well dye coupled, and lack P2U receptors, transmitted slow gap junction-dependent calcium waves that did not require release of intracellular calcium stores. UMR 106-01 cells predominantly express the gap junction protein connexin 45 (Cx45), are poorly dye coupled, and express P2U receptors; they propagated fast calcium waves that required release of intracellular calcium stores and activation of P2U purinergic receptors, but not gap junctional communication. ROS/P2U transfectants and UMR/Cx43 transfectants expressed both types of calcium waves. Gap junction-independent, ATP-dependent intercellular calcium waves were also seen in hamster tracheal epithelia cells. These studies demonstrate that activation of P2U purinergic receptors can propagate intercellular calcium, and describe a novel Cx43-dependent mechanism for calcium wave propagation that does not require release of intracellular calcium stores by IP3. These studies suggest that gap junction communication mediated by either Cx43 or Cx45 does not allow passage of IP3 well enough to elicit release of intracellular calcium stores in neighboring cells.

Show MeSH
Related in: MedlinePlus