Mitochondrial Small Conductance SK2 Channels Prevent Glutamate-induced Oxytosis and Mitochondrial Dysfunction

Dolga, Amalia M.; Netter, Michael F.; Perocchi, Fabiana; Doti, Nunzianna; Meissner, Lilja; Tobaben, S; Grohm, Julia; Zischka, Hans; Plesnila, Nikolaus; Decher, Niels; Culmsee, Carsten

doi:10.1074/jbc.m113.453522

Cited by 83 publications

(86 citation statements)

References 53 publications

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“…Recent reports demonstrate the presence of the mitochondrial SK channel in neuronal cell types and show that potassium influx into mitochondria causes changes in the membrane potential (38,39). Although such mitochondrial potassium channels have not been identified in neutrophils, our results suggest that activation of SK channels leads to the production of mitochondrial ROS in neutrophils (Fig.…”

Section: Discussionmentioning

confidence: 38%

“…Moreover, although apamin is a cell-impermeable inhibitor peptide, it exerts an inhibitory effect on NETosis that suggests the engagement of cell surface SK3 in this process. It has been shown that changes in cytosolic potassium levels can change potassium flux and mitochondrial respiration (39). Furthermore, a unique feature of the SK channel complex is that it contains a calmodulin-binding domain.…”

Section: Discussionmentioning

confidence: 99%

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SK3 channel and mitochondrial ROS mediate NADPH oxidase-independent NETosis induced by calcium influx

Douda¹,

Khan²,

Grasemann

et al. 2015

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

482

584

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Neutrophils cast neutrophil extracellular traps (NETs) to defend the host against invading pathogens. Although effective against microbial pathogens, a growing body of literature now suggests that NETs have negative impacts on many inflammatory and autoimmune diseases. Identifying mechanisms that regulate the process termed “NETosis” is important for treating these diseases. Although two major types of NETosis have been described to date, mechanisms regulating these forms of cell death are not clearly established. NADPH oxidase 2 (NOX2) generates large amounts of reactive oxygen species (ROS), which is essential for NOX-dependent NETosis. However, major regulators of NOX-independent NETosis are largely unknown. Here we show that calcium activated NOX-independent NETosis is fast and mediated by a calcium-activated small conductance potassium (SK) channel member SK3 and mitochondrial ROS. Although mitochondrial ROS is needed for NOX-independent NETosis, it is not important for NOX-dependent NETosis. We further demonstrate that the activation of the calcium-activated potassium channel is sufficient to induce NOX-independent NETosis. Unlike NOX-dependent NETosis, NOX-independent NETosis is accompanied by a substantially lower level of activation of ERK and moderate level of activation of Akt, whereas the activation of p38 is similar in both pathways. ERK activation is essential for the NOX-dependent pathway, whereas its activation is not essential for the NOX-independent pathway. Despite the differential activation, both NOX-dependent and -independent NETosis require Akt activity. Collectively, this study highlights key differences in these two major NETosis pathways and provides an insight into previously unknown mechanisms for NOX-independent NETosis.

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Section: Discussionmentioning

confidence: 38%

Section: Discussionmentioning

confidence: 99%

SK3 channel and mitochondrial ROS mediate NADPH oxidase-independent NETosis induced by calcium influx

Douda¹,

Khan²,

Grasemann

et al. 2015

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

482

584

View full text Add to dashboard Cite

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“…It is well established that neuronal cell death is accompanied by fragmentation of the tubular mitochondrial network, loss of mitochondrial membrane potential (ΔΨm) and associated defects in mitochondrial bioenergetics. 18,27 Brefeldin A (24 h) increased the amount of cells showing shortened and fragmented mitochondria in the perinuclear region ( Figure 5a and b), indicating mitochondrial damage in dying cells. 28 Additionally, brefeldin A exposure resulted in a slight depolarization of ΔΨm, decreased basal mitochondrial respiration, ATP production and spare respiratory capacity (Figure 5c-e).…”

Section: Resultsmentioning

confidence: 99%

“…To further prove the topology of SK2 channels at the level of ER membranes, we performed subcellular fractionation analysis of HT-22 neurons. Besides plasma membrane and mitochondrial localization, 18 the utilized subtype specific antibody identified SK2 channel also at the ER microsome-enriched protein fraction (Figure 7b and Supplementary Figure S8). These data demonstrate an intracellular residence of SK2 channels at the ER membrane of neuronal HT-22 cells, with potential importance for the CyPPA-mediated protective effects against ER stress.…”

Section: Resultsmentioning

confidence: 99%

“…To investigate the effects of SK channel activation in this model of ER stress-induced cell death, we applied cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA), a positive modulator of SK channels, selective for SK2 and SK3. 17 Since SK3 channels are not expressed in immortalized HT-22 cells, 18 the use of CyPPA allowed selective investigation of SK2 channel activation. Co-application of CyPPA (50 μM) with brefeldin A mediated a slight protection against ER stress-induced cell death (Supplementary Figure S1A).…”

Section: Resultsmentioning

confidence: 99%

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Activation of SK2 channels preserves ER Ca2+ homeostasis and protects against ER stress-induced cell death

et al. 2015

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Alteration of endoplasmic reticulum (ER) Ca2+ homeostasis leads to excessive cytosolic Ca 2+ accumulation and delayed neuronal cell death in acute and chronic neurodegenerative disorders. While our recent studies established a protective role for SK channels against excessive intracellular Ca 2+ accumulation, their functional role in the ER has not been elucidated yet. We show here that SK2 channels are present in ER membranes of neuronal HT-22 cells, and that positive pharmacological modulation of SK2 channels with CyPPA protects against cell death induced by the ER stressors brefeldin A and tunicamycin. Calcium imaging of HT-22 neurons revealed that elevated cytosolic Ca 2+ levels and decreased ER Ca 2+ load during sustained ER stress could be largely prevented by SK2 channel activation. Interestingly, SK2 channel activation reduced the amount of the unfolded protein response transcription factor ATF4, but further enhanced the induction of CHOP. Using siRNA approaches we confirmed a detrimental role for ATF4 in ER stress, whereas CHOP regulation was dispensable for both, brefeldin A toxicity and CyPPA-mediated protection. Cell death induced by blocking Ca 2+ influx into the ER with the SERCA inhibitor thapsigargin was not prevented by CyPPA. Blocking the K + efflux via K + /H + exchangers with quinine inhibited CyPPA-mediated neuroprotection, suggesting an essential role of proton uptake and K + release in the SK channel-mediated neuroprotection. Our data demonstrate that ER SK2 channel activation preserves ER Ca 2+ uptake and retention which determines cell survival in conditions where sustained ER stress contributes to progressive neuronal death.

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Plasma membrane SK2 channel activity regulates migration and chemosensitivity of high‐grade serous ovarian cancer cells

Romito,

Lemettre,

Chantôme

et al. 2024

Molecular Oncology

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No data are currently available on the functional role of small conductance Ca2+‐activated K+ channels (SKCa) in ovarian cancer. Here, we characterized the role of SK2 (KCa2.2) in ovarian cancer cell migration and chemosensitivity. Using the selective non‐cell‐permeant SK2 inhibitor Lei‐Dab7, we identified functional SK2 channels at the plasma membrane, regulating store‐operated Ca2+ entry (SOCE) in both cell lines tested (COV504 and OVCAR3). Silencing KCNN2 with short interfering RNA (siRNA), or blocking SK2 activity with Lei‐Dab7, decreased cell migration. The more robust effect of KCNN2 knockdown compared to Lei‐Dab7 treatment suggested the involvement of functional intracellular SK2 channels in both cell lines. In cells treated with lysophosphatidic acid (LPA), an ovarian cancer biomarker of progression, SK2 channels are a key player of LPA pro‐migratory activity but their role in SOCE is abolished. Concerning chemotherapy, SK2 inhibition increased chemoresistance to Taxol® and low KCNN2 mRNA expression was associated with the worst prognosis for progression‐free survival in patients with serous ovarian cancer. The dual roles of SK2 mean that SK2 activators could be used as an adjuvant chemotherapy to potentiate treatment efficacy and SK2 inhibitors could be administrated as monotherapy to limit cancer cell dissemination.

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Mitochondrial Small Conductance SK2 Channels Prevent Glutamate-induced Oxytosis and Mitochondrial Dysfunction

Cited by 83 publications

References 53 publications

SK3 channel and mitochondrial ROS mediate NADPH oxidase-independent NETosis induced by calcium influx

SK3 channel and mitochondrial ROS mediate NADPH oxidase-independent NETosis induced by calcium influx

Activation of SK2 channels preserves ER Ca2+ homeostasis and protects against ER stress-induced cell death

Plasma membrane SK2 channel activity regulates migration and chemosensitivity of high‐grade serous ovarian cancer cells

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