Bile acids activate ryanodine receptors in pancreatic acinar cells via a direct allosteric mechanism

Geyer, Nikolett; Diszházi, Gyula; Csernoch, László; Jóna, István; Almássy, János

doi:10.1016/j.ceca.2015.03.009

Cited by 16 publications

(13 citation statements)

References 36 publications

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“…Heavy sarcoplasmic reticulum (HSR) vesicles were isolated from rabbit skeletal muscle by differential centrifugation as described in the literature (45,46). All the steps were performed on ice or at 4 C in the presence of protease inhibitors.…”

Section: Heavy Sarcoplasmic Reticulum Vesicle Isolationmentioning

confidence: 99%

Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor

Sárközi

Komáromi

Jóna

et al. 2017

Biophysical Journal

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Ca regulates ryanodine receptor's (RyR) activity through an activating and an inhibiting Ca-binding site located on the cytoplasmic side of the RyR channel. Their altered sensitivity plays an important role in the pathology of malignant hyperthermia and heart failure. We used lanthanide ions (Ln) as probes to investigate the Ca sensors of RyR, because they specifically bind to Ca-binding proteins and they are impermeable to the channel. Eu's and Sm's action was tested on single RyR1 channels reconstituted into planar lipid bilayers. When the activating binding site was saturated by 50 μM Ca, Ln potently inhibited RyR's open probability (K Eu = 167 ± 5 nM and K Sm = 63 ± 3 nM), but in nominally 0 [Ca], low [Eu] activated the channel. These results suggest that Ln acts as an agonist of both Ca-binding sites. More importantly, the voltage-dependent characteristics of Ln's action led to the conclusion that the activating Ca binding site is located within the electrical field of the channel (in the vestibule). This idea was tested by applying the pore blocker toxin maurocalcine on the cytoplasmic side of RyR. These experiments showed that RyR lost reactivity to changing cytosolic [Ca] from 50 μM to 100 nM when the toxin occupied the vestibule. These results suggest that maurocalcine mechanically prevented Ca from dissociating from its binding site and support our vestibular Ca sensor-model further.

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Section: Heavy Sarcoplasmic Reticulum Vesicle Isolationmentioning

confidence: 99%

Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor

Sárközi

Komáromi

Jóna

et al. 2017

Biophysical Journal

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“…Both FXR and TGR5 demonstrate pleiotropic functions, including immune modulation. Recently it was found that bile acids can also activate ryanodine receptors [155], which are the major cellular mediator of calcium-induced calcium release. Although current studies shown a role of FPR in liver injury (e.g., [156]), involvement of bile acids as FPR1 ligands in liver pathology is still unknown.…”

Section: Small-molecule Non-peptide Fpr1 Antagonists and Their Synmentioning

confidence: 99%

Antagonism of human formyl peptide receptor 1 with natural compounds and their synthetic derivatives

Schepetkin

Khlebnikov

Kirpotina

et al. 2016

International Immunopharmacology

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Formyl peptide receptor 1 (FPR1) regulates a wide variety of neutrophil functional responses and plays an important role in inflammation and the pathogenesis of various diseases. To date, a variety of natural and synthetic molecules have been identified as FPR1 ligands. Here, we review current knowledge on natural products and natural product-inspired small-molecules reported to antagonize and/or inhibit the FPR1-mediated responses. Based on this literature, additional screening of selected commercially available natural compounds for their ability to inhibit fMLF-induced Ca2+ mobilization in human neutrophils and FPR1 transfected HL-60 cells, and pharmacophore modeling, natural products with potential as FPR1 antagonists are considered and discussed in this review. The identification and characterization of natural products that antagonize FPR1 activity may have potential for the development of novel therapeutics to limit or alter the outcome of inflammatory processes.

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“…The cell pellet was resuspended and collected by centrifugation. Acinar cell clumps were gently resuspended in F12/DMEM medium and kept gassed at room temperature until use (Geyer et al 2015).…”

Section: Pancreatic Acinar Cell Isolationmentioning

confidence: 99%

“…HEK293 cells and HaCaT keratinocytes were cultured in DMEM medium supplemented with 10% fetal bovine serum (FBS) at 37° in a CO 2 thermostat (Geyer et al 2015). Cells were allowed to grow to 60-70% confluence.…”

Section: Cell Culturesmentioning

confidence: 99%

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Laser induced calcium oscillations in fluorescent calcium imaging

Vincze

Geyer²,

Diszházi³

et al. 2018

gpb

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Phototoxicity is the most common problem investigators may encounter when performing live cell imaging. It develops due to excess laser exposure of cells loaded with fluorophores and can lead to often overlooked but significant artifacts, such as massive increase of intracellular Ca2+ concentration, which would make data interpretation problematic. Because information about laser- and dye-related changes in cytoplasmic calcium concentration is very limited, we aimed to describe this phenomenon to help investigators using laser scanning confocal microscopy in a non-invasive way. Therefore, in the present study we evaluated fluorescent fluctuations, which evolved in Fluo-3/4/8 loaded mouse pancreatic acinar cells during very low intensity laser excitation. We demonstrate that after standard loading procedure (2 µM Fluo-3/4/8-AM, 30 min at room temperature), applying 488 nm laser at as low as ca. 10 µW incident laser power (0.18 µW/µm2) at 1 Hz caused repetitive, 2-3 fold elevations of the resting intracellular fluorescence. The first latency and the pattern of the fluorescence fluctuations were laser power dependent and were related to Ca2+-release from intracellular stores, as they were abolished by BAPTA-AM treatment in Ca2+-free medium, but were not diminished by the reactive oxygen species (ROS) scavenger DMPO. Worryingly enough, the qualitative and quantitative features of the Ca2+-waves were practically indistinguishable from the responses evoked by secretagogue stimulation. Since using similar imaging conditions, a number of other cell types were reported to display spontaneous Ca2+ oscillations, we propose strategies to distinguish the real signals from artifacts.

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Bile acids activate ryanodine receptors in pancreatic acinar cells via a direct allosteric mechanism

Cited by 16 publications

References 36 publications

Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor

Lanthanides Report Calcium Sensor in the Vestibule of Ryanodine Receptor

Antagonism of human formyl peptide receptor 1 with natural compounds and their synthetic derivatives

Laser induced calcium oscillations in fluorescent calcium imaging

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