Calcium release induced by inositol 1,4,5-trisphosphate in thymocyte microsomes. Inhibition by barium and strontium

Baquero-Leonis, Domingo; Pintado, Elı́zabeth

doi:10.1016/0143-4160(89)90022-5

Cited by 10 publications

(5 citation statements)

References 16 publications

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“…The finding that Ba2+ and Sr2+ are able to substitute for Ca2+ in facilitating the action of InsP3 may provide a useful tool for further investigation of the mechanism of the facilitation. Differing with our results, Baquero-Leonis & Pintado (1989) reported that these ions inhibited InsP3-mediated Ca2+ release in thymocyte microsomes. However, this discrepancy might have arisen through differences in experimental procedures if the actions of Ba2+ and Sr2+ are like those of Ca2+, and show both time and dose dependence.…”

Section: Mechanism Of Ca2+ Facilitationcontrasting

confidence: 99%

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Yao

Parker

1992

The Journal of Physiology

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Section: Mechanism Of Ca2+ Facilitationcontrasting

confidence: 99%

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Yao

Parker

1992

The Journal of Physiology

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“…Further differences in the characteristics of these regulatory effects of cytosolic Ca2+ between tissues are evident when Ca2+ is substituted for other bivalent cations. For example, Sr2+ mimics Ca2+ in potentiating Ins (1,4,5)P3 binding to liver Ins(1,4,5)P3 receptors (Table 1), but it has no effect on the binding of Ins(1,4,5)P3 to cerebellar Ins(1,4,5)P3 receptors (Worley et al, stimulated Ca2' release in liver (Figure 4), it reportedly potentiates Ca2+ release in Xenopus oocytes (Yao and Parker, 1992) and inhibits Ca2+ release in thymocytes (Baquero-Leonis and Pintado, 1989). Some of the apparent differences in the effects of bivalent cations on Ins (1,4,5)P3-stimulated Ca2+ release, however, may arise from the changes in cytosolic [Ca2+] that occur as a result of the displacement of Ca2+ from buffers following addition of Ba2+ or Sr2 .…”

Section: Discussionmentioning

confidence: 97%

Two calcium-binding sites mediate the interconversion of liver inositol 1,4,5-trisphosphate receptors between three conformational states

Marshall

Taylor

1994

Biochemical Journal

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Cytosolic Ca2+ biphasically regulates Ins(1,4,5)P3-stimulated Ca2+ mobilization in liver [Marshall and Taylor (1993) J. Biol. Chem. 268, 13214-13220]. We have investigated the mechanisms underlying this biphasic control of Ca2+ mobilization in permeabilized hepatocytes by comparing the effects of Sr2+, Ba2+ and Ca2+ on the liver Ins(1,4,5)P3 receptor. Both Ca2+ and Sr2+ increased the binding of [3H]Ins(1,4,5)P3 to liver membranes by converting receptors from a low-affinity (KD approximately 35 nM) to a high-affinity (KD approximately 5 nM) state. Ba2+ (< or = 20 microM) did not affect [3H]Ins(1,4,5)P3 binding. At concentrations similar to those that caused an enhancement of [3H]Ins(1,4,5)P3 binding, Sr2+ (EC50 = 570 nM) and Ca2+ (EC50 = 200 nM) increased the sensitivity of the intracellular Ca2+ stores to Ins(1,4,5)P3. Further modest elevations in [Ca2+] (EC50 = 1.5 microM) inhibited Ins(1,4,5)P3-stimulated Ca2+ mobilization, whereas Sr2+ caused inhibition only when its concentration was very substantially increased (EC50 approximately 900 microM). Sr2+ is therefore only 3-fold less potent than Ca2+ in causing sensitization of Ins(1,4,5)P3-stimulated Ca2+ release, but 600-fold less potent in causing inhibition. Ba2+ neither sensitized ([Ba2+] < or = 20 microM) nor inhibited ([Ba2+] < or = 1 mM) Ins(1,4,5)P3-stimulated Ca2+ release, and did not inhibit either the sensitization of Ca2+ release evoked by Sr2+ or the inhibition of Ca2+ release evoked by Ca2+. Our results suggest that two distinct Ca(2+)-binding sites, which differ in their selectivities for bivalent cations, mediate the interconversion of Ins(1,4,5)P3 receptors between at least three different conformational states. These two Ca(2+)-binding sites, which may reside either on the Ins(1,4,5)P3 receptor itself or on distinct regulatory proteins, can be distinguished by their different selectivities for bivalent cations.

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“…Such inhibition can be expected, because the release of Ca 2ϩ from stores is conditional on charge balance by some other ion, and there is direct evidence by using either tetraethyl ammonium or Ba 2ϩ as K ϩ channel blockers of dependence of IP 3 -triggered Ca 2ϩ release on a balancing K ϩ flux in both animals and plants (26)(27)(28). It is therefore plausible to expect that Ba 2ϩ , acting in its capacity as a K ϩ channel blocker, could block Ca 2ϩ release from internal stores, thereby interfering with the initiation of the vacuolar efflux transient.…”

Section: Discussionmentioning

confidence: 99%

ABA activates multiple Ca ²⁺ fluxes in stomatal guard cells, triggering vacuolar K ⁺ (Rb ⁺ ) release

Macrobbie

2000

Proc. Natl. Acad. Sci. U.S.A.

160

106

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The mechanisms by which abscisic acid (ABA) activates the release of K ؉ (Rb ؉ ) from the vacuole of stomatal guard cells, a process essential for ABA-induced stomatal closure, have been investigated by tracer flux measurements. The form and timing of the ABA-induced efflux transient could be manipulated by treatments that alter three potential Ca 2؉ fluxes into the cytoplasm, the influx from the outside and two pathways of internal release, those dependent on phospholipase C (inhibited by U73122) and cyclic ADP-ribose (inhibited by nicotinamide). Ba 2؉ , acting as a competitive inhibitor of Ca 2؉ influx but also as an inhibitor of internal release, was an effective inhibitor of the transient. The results suggest that a threshold level of cytoplasmic Ca 2؉ is required for the initiation of the minimal efflux transient after a lag period and with a low rate of rise. As conditions improve for the generation of an efflux transient (higher ABA or reduced Ba 2؉ ), a second threshold is crossed, generating a transient with zero lag and rapid rate of rise. This may reflect different Ca 2؉ levels required for activation of different tonoplast K ؉ channels. In this state, at high ABA, the transient is inhibited by removal of external Ca 2؉ , suggesting Ca 2؉ influx makes a major contribution to increase in cytoplasmic Ca 2؉ . By contrast, at low ABA, the transient is not inhibited by removal of external Ca 2؉ but is sensitive to either U73122 or nicotinamide, suggesting internal release makes the major contribution, involving both pathways. ABA appears to activate all three processes, and their relative importance depends on conditions.T he ability to reduce transpirational water loss when water is scarce is essential for plant survival, and such control is achieved by regulation of the size of stomatal pores in the leaf surface. Pore size is determined by the turgor of the pair of stomatal guard cells and is modified by changes in guard cell solute content, largely potassium salts, but also other solutes including sugars. The so-called drought hormone, abscisic acid (ABA), is produced by or imported into stomatal guard cells in water stress conditions, changing the activity of a number of ion channels in guard cell membranes to produce net loss of salt from guard cells and loss of turgor with consequent closure of the stomatal pore. The end result is the loss of both K ϩ and associated anion (Cl Ϫ and͞or malate) from both the vacuole and the cell by up-regulation of appropriate channels in the two membranes. Commonly there is discussion about signaling pathways involved in the process of stomatal closure, as if this were a single process, with debate about whether these pathways are (for example) Ca 2ϩ dependent or Ca 2ϩ independent. This view is inadequate and seriously misleading. Instead, we need to distinguish the essential contributory processes and their signaling chains, the four separate stimulations of transport activities by which net efflux of K ϩ and anions at the plasmalemma and net flux of K ϩ and anions f...

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Calcium release induced by inositol 1,4,5-trisphosphate in thymocyte microsomes. Inhibition by barium and strontium

Cited by 10 publications

References 16 publications

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Two calcium-binding sites mediate the interconversion of liver inositol 1,4,5-trisphosphate receptors between three conformational states

ABA activates multiple Ca ²⁺ fluxes in stomatal guard cells, triggering vacuolar K ⁺ (Rb ⁺ ) release

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Calcium release induced by inositol 1,4,5-trisphosphate in thymocyte microsomes. Inhibition by barium and strontium

Cited by 10 publications

References 16 publications

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Potentiation of inositol trisphosphate‐induced Ca2+ mobilization in Xenopus oocytes by cytosolic Ca2+.

Two calcium-binding sites mediate the interconversion of liver inositol 1,4,5-trisphosphate receptors between three conformational states

ABA activates multiple Ca 2+ fluxes in stomatal guard cells, triggering vacuolar K + (Rb + ) release

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ABA activates multiple Ca ²⁺ fluxes in stomatal guard cells, triggering vacuolar K ⁺ (Rb ⁺ ) release