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

Yao, Yong; Parker, Ian

doi:10.1113/jphysiol.1992.sp019420

Cited by 78 publications

(51 citation statements)

References 42 publications

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“…The decrease in Ca 2ϩ wave amplitude in the center of the egg probably relates to spatial differences in sensitivity to Ca 2ϩ -releasing messengers, as discussed below; the important feature is the constant velocity throughout the irradiated area. This response is similar to that reported for IP 3 when it was uncaged in half of a Xenopus oocyte because the resulting regenerative Ca 2ϩ wave was limited to the half of the egg being irradiated (25). In both the Xenopus oocyte (25) and the sea urchin egg (Fig.…”

Section: Spatial Control Of Ca 2ϩsupporting

confidence: 81%

“…Even though the Ca 2ϩ wave is propagated by NAADP diffusion, the wave does not decrease in velocity or amplitude because NAADP is continuously added to the other half of the egg. This result shows that a diffusive wave propagates by CICR (9,14,25). Because cADPR acts by sensitizing ryanodine receptors to CICR (13), it should elicit a regenerative rather than diffusive Ca 2ϩ wave similar to that induced by IP 3 (9,14,25).…”

Section: Spatial Control Of Ca 2ϩmentioning

confidence: 82%

“…This result shows that a diffusive wave propagates by CICR (9,14,25). Because cADPR acts by sensitizing ryanodine receptors to CICR (13), it should elicit a regenerative rather than diffusive Ca 2ϩ wave similar to that induced by IP 3 (9,14,25). To provide further evidence that NAADP-mediated Ca 2ϩ waves are dependent on a non-regenerative diffusive mechanism, the responses of cADPR and NAADP were compared at their threshold concentrations for evoking Ca 2ϩ release.…”

Section: Spatial Control Of Ca 2ϩmentioning

confidence: 95%

“…2ϩ wave shows a constant amplitude and velocity (7)(8)(9)25), whereas a diffusive Ca 2ϩ wave shows a decrease in amplitude and velocity with time (26). Photorelease of NAADP in a band at the edge of an egg resulted in an immediate increase in Ca 2ϩ in this region, which then spread across the cell with a decrease in amplitude and velocity (Fig.…”

Section: Naadp-mediated Ca 2ϩ Waves Spread By Naadp Diffusion-a Regenmentioning

confidence: 99%

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Spatial Control of Ca2+ Signaling by Nicotinic Acid Adenine Dinucleotide Phosphate Diffusion and Gradients

Churchill

Galione

2000

Journal of Biological Chemistry

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Section: Spatial Control Of Ca 2ϩsupporting

confidence: 81%

Section: Spatial Control Of Ca 2ϩmentioning

confidence: 82%

Section: Spatial Control Of Ca 2ϩmentioning

confidence: 95%

Section: Naadp-mediated Ca 2ϩ Waves Spread By Naadp Diffusion-a Regenmentioning

confidence: 99%

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Spatial Control of Ca2+ Signaling by Nicotinic Acid Adenine Dinucleotide Phosphate Diffusion and Gradients

Churchill

Galione

2000

Journal of Biological Chemistry

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“…One of the most important of these mechanisms is the inositol trisphosphate receptor (IPR), which also functions as a Ca 2ϩ channel. There is now a great deal of experimental evidence that in many cell types, oscillations and waves of Ca 2ϩ are mediated in major part by the release through the IPR of Ca 2ϩ from the endoplasmic reticulum, and that it is the modulation of the IPR by Ca 2ϩ and by inositol (1,4,5)-trisphosphate (IP 3 ) that causes such complex dynamic behavior (1)(2)(3)(4)(5)(6)(7).…”

mentioning

confidence: 99%

A dynamic model of the type-2 inositol trisphosphate receptor

Sneyd

Dufour

2002

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

113

118

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The dynamic properties of the inositol (1,4,5)-trisphosphate (IP3) receptor are crucial for the control of intracellular Ca 2؉ , including the generation of Ca 2؉ oscillations and waves. However, many models of this receptor do not agree with recent experimental data on the dynamic responses of the receptor. We construct a model of the IP 3 receptor and fit the model to dynamic and steady-state experimental data from type-2 IP 3 receptors. Our results indicate that, (i) Ca 2؉ binds to the receptor using saturating, not mass-action, kinetics; (ii) Ca 2؉ decreases the rate of IP 3 binding while simultaneously increasing the steady-state sensitivity of the receptor to IP 3; (iii) the rate of Ca 2؉ -induced receptor activation increases with Ca 2؉ and is faster than Ca 2؉ -induced receptor inactivation; and (iv) IP3 receptors are sequentially activated and inactivated by Ca 2؉ even when IP3 is bound. Our results emphasize that measurement of steady-state properties alone is insufficient to characterize the functional properties of the receptor. O scillations and waves in the concentration of free intracellular calcium (Ca 2ϩ ) are seen in many cell types and are known to be an important intra-and intercellular signaling system. It is thus of interest to determine the mechanisms underlying such complex dynamic behavior. One of the most important of these mechanisms is the inositol trisphosphate receptor (IPR), which also functions as a Ca 2ϩ channel. There is now a great deal of experimental evidence that in many cell types, oscillations and waves of Ca 2ϩ are mediated in major part by the release through the IPR of Ca 2ϩ from the endoplasmic reticulum, and that it is the modulation of the IPR by Ca Consider, for example, the reaction scheme shown in Fig. 1. If we assume that Ã and Ā are in instantaneous equilibrium, we have cÃ ϭ L 1 Ā , where L 1 ϭ l Ϫ1 ͞l 1 , and c denotes [Ca 2ϩ ]. Hence, letting A ϭ Ā ϩ Ã , we have dA͞dt ϭ (k Ϫ1 ϩ l Ϫ2 )I Ϫ (c)A, where (c) ϭ c(k 1 L 1 ϩl 2 )͞cϩL 1 . Thus, this scheme is a simple way in which saturating binding kinetics can be incorporated into a model. It is similar to the Michaelis-Menten model of an enzyme-catalyzed reaction, in which a saturating reaction rate is obtained by assuming the existence of an intermediate complex. In this introductory model, the state Ā plays a role similar to that of the enzyme complex. By assuming that the original state Ã (analogous to the substrate) is in fast equilibrium with state Ā , we attain saturating kinetics of the Michaelis-Menten type. An IPR ModelA diagram of the IPR model is given in Fig. 2. Although it appears to contain a multiplicity of states, there are specific reasons for each one. The background structure is simple. Fig. 3.States R , Ō , Ā , and RЈ are used to give Ca 2ϩ -dependent transitions that have saturable kinetics, as in the simple example of Fig. 1. These states will ultimately disappear, leaving behind only functions of c. Note that the inactivated states I 1 and I 2 both have Ca 2ϩ bound to the same site...

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