Highly Sensitive Measurement of Inositol 1,4,5‐Trisphosphate by Using a New Fluorescent Ligand and Ligand Binding Domain Combination

Oura, Tai; Murata, Keiji; Mitsui, Takao; Nezu, Akihiro; Arisawa, Mitsuhiro; Shuto, Satoshi; Tanimura, Akihiko

doi:10.1002/cbic.201600096

Cited by 14 publications

(10 citation statements)

References 31 publications

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“…In a subset of simulations, we have replaced our non-cooperative IP 3 R model, in which the binding of a single IP 3 site is enough to open the monomer channel, with the cooperative model proposed by Bicknell and collaborators [84]. With 100 nM basal IP 3 and Ca 2+ [85, 86], we could not produce spontaneous calcium signals in these conditions, even after a search of the parameter space to locate parameters allowing spontaneous activity with this cooperative model. This issue might reflect a general problem of the De Young Keizer model in discrete particle-based models with low copy number of particles.…”

Section: Discussionmentioning

confidence: 99%

“…γ and α values were adjusted to yield basal calcium concentration around 120 nM [86, 124]. Likewise, β and μ were adjusted for a basal IP 3 concentration of 120nM [85]. Note that this value is based on recent, precise measurements of IP 3 concentration and differs by an order of magnitude from IP 3 concentration values routinely used in IP 3 R -mediated calcium models [59, 125, 126].…”

Section: Methodsmentioning

confidence: 99%

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Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity

et al. 2019

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Astrocytes, a glial cell type of the central nervous system, have emerged as detectors and regulators of neuronal information processing. Astrocyte excitability resides in transient variations of free cytosolic calcium concentration over a range of temporal and spatial scales, from sub-microdomains to waves propagating throughout the cell. Despite extensive experimental approaches, it is not clear how these signals are transmitted to and integrated within an astrocyte. The localization of the main molecular actors and the geometry of the system, including the spatial organization of calcium channels IP 3 R , are deemed essential. However, as most calcium signals occur in astrocytic ramifications that are too fine to be resolved by conventional light microscopy, most of those spatial data are unknown and computational modeling remains the only methodology to study this issue. Here, we propose an IP 3 R -mediated calcium signaling model for dynamics in such small sub-cellular volumes. To account for the expected stochasticity and low copy numbers, our model is both spatially explicit and particle-based. Extensive simulations show that spontaneous calcium signals arise in the model via the interplay between excitability and stochasticity. The model reproduces the main forms of calcium signals and indicates that their frequency crucially depends on the spatial organization of the IP 3 R channels. Importantly, we show that two processes expressing exactly the same calcium channels can display different types of calcium signals depending on the spatial organization of the channels. Our model with realistic process volume and calcium concentrations successfully reproduces spontaneous calcium signals that we measured in calcium micro-domains with confocal microscopy and predicts that local variations of calcium indicators might contribute to the diversity of calcium signals observed in astrocytes. To our knowledge, this model is the first model suited to investigate calcium dynamics in fine astrocytic processes and to propose plausible mechanisms responsible for their variability.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity

et al. 2019

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“…We showed that IP3, as well as AdA, could interfere with BH4-Bcl-2 binding to the LBD of IP3R1. To address the opposite question, namely whether BH4-Bcl-2 might affect the interaction of IP3 with the LBD, we performed FRET-based measurements using a competitive fluorescent ligand assay for IP3 [46]. In this method, binding of a fluorescent low-affinity ligand (FLL) and a fluorescent IP3-binding protein (CFP-coupled LBD) generates FRET signals.…”

Section: C)mentioning

confidence: 99%

Bcl-2 and IP3 compete for the ligand-binding domain of IP3Rs modulating Ca2+ signaling output

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Wagner

Tanimura

et al. 2019

Cell. Mol. Life Sci.

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Bcl-2 protein has emerged as a critical regulator of intracellular Ca 2+ dynamics by directly targeting and inhibiting the IP3 receptor (IP3R), a major intracellular Ca 2+ -release channel. Here, we demonstrate that such inhibition occurs under conditions of basal, but not high IP3R activity, since overexpressed and purified Bcl-2 (or its BH4 domain) can inhibit IP3R function provoked by low concentration of agonist or IP3, while fails to attenuate against high concentration of agonist or IP3. Surprisingly, Bcl-2 remained capable of inhibiting IP3R1 channels lacking the residues encompassing the previously identified Bcl-2-binding site (a.a. 1380-1408) located in the ARM2 domain, part of the modulatory region. Using a plethora of computational, biochemical and biophysical methods, we demonstrate that Bcl-2 and more particularly its BH4 domain bind to the ligand-binding domain (LBD) of IP3R1. In line with this finding, the interaction between the LBD and Bcl-2 (or its BH4 domain) was sensitive to IP3 and adenophostin A, ligands of the IP3R. Consistent with this, the BH4 domain of Bcl-2 counteracted the binding of IP3 to the LBD. Collectively, our work reveals a novel mechanism by which Bcl-2 influences IP3R activity at the level of the LBD. This allows for exquisite modulation of Bcl-2's inhibitory properties on IP3Rs that is tunable to the level of IP3 signaling in cells.

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“…C)にルイス酸存在下における C-アリル化の結果を示すように，ラジカル反応だけでなくの S N 1 型 C-グリコシル化にも適用できる． 89,91) さらには O-グリコシル化へも適用可能であり，IP 3 受容体リガンド 12 及び 14(Fig. 15)の a-O-グリコシド結合は，本法を用いて高立体選択的に構築した．49,50,52) …”

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“…Fig. 15) ． 43 52) その結果，IP 3 様の Ca 2＋動員活性を持つ 13， 47) IP 3 受容体サブタイプ I 選択的アゴニスト 14， 50) バイオツール合成前駆体 1549,52) …”

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Highly Sensitive Measurement of Inositol 1,4,5‐Trisphosphate by Using a New Fluorescent Ligand and Ligand Binding Domain Combination

Cited by 14 publications

References 31 publications

Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity

Simulation of calcium signaling in fine astrocytic processes: Effect of spatial properties on spontaneous activity

Bcl-2 and IP3 compete for the ligand-binding domain of IP3Rs modulating Ca2+ signaling output

Medicinal Chemical Studies Based on the Theoretical Design of Bioactive Compounds

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