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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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Kinetics of calcium  wave propagation in ROS  and UMR cells. Four cells in  a row from the stimulated  cells were analyzed from the  sequences shown in Figs. 2  and 3. Data are presented as  relative fluorescence ratio.
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Figure 4: Kinetics of calcium wave propagation in ROS and UMR cells. Four cells in a row from the stimulated cells were analyzed from the sequences shown in Figs. 2 and 3. Data are presented as relative fluorescence ratio.

Mentions: To demonstrate the differences in the kinetics of these calcium waves graphically, we identified four cells in a row extending outward from the mechanically stimulated cell, and measured fura-2 ratios in these cells over time (Fig. 4). These traces confirm the dramatic differences in calcium wave kinetics between the two cell lines. It should be noted that these traces are presented to demonstrate kinetics and not the intensity of the response. Thus they are presented in relative fluorescence ratios, and the ROS cells demonstrate a saturating response. It should also be noted that although UMR cells in these traces demonstrate an attenuating response, frequently the response in these cells does not attenuate significantly, as is seen in Fig. 3.


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

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

Kinetics of calcium  wave propagation in ROS  and UMR cells. Four cells in  a row from the stimulated  cells were analyzed from the  sequences shown in Figs. 2  and 3. Data are presented as  relative fluorescence ratio.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 4: Kinetics of calcium wave propagation in ROS and UMR cells. Four cells in a row from the stimulated cells were analyzed from the sequences shown in Figs. 2 and 3. Data are presented as relative fluorescence ratio.
Mentions: To demonstrate the differences in the kinetics of these calcium waves graphically, we identified four cells in a row extending outward from the mechanically stimulated cell, and measured fura-2 ratios in these cells over time (Fig. 4). These traces confirm the dramatic differences in calcium wave kinetics between the two cell lines. It should be noted that these traces are presented to demonstrate kinetics and not the intensity of the response. Thus they are presented in relative fluorescence ratios, and the ROS cells demonstrate a saturating response. It should also be noted that although UMR cells in these traces demonstrate an attenuating response, frequently the response in these cells does not attenuate significantly, as is seen in Fig. 3.

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