Activation of SK2 channels preserves ER Ca2+ homeostasis and protects against ER stress-induced cell death
Activation of SK2 channels preserves ER Ca2+ homeostasis and protects against ER stress-induced cell death
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DOI：
10.1038/cdd.2015.146
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发表时间：
2015-11
影响因子：
12.4
通讯作者：
Maren Richter;N. Vidovic;B. Honrath;P. Mahavadi;Richard Dodel;A. Dolga;Carsten Culmsee
中科院分区：
文献类型：
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作者：
Maren Richter;N. Vidovic;B. Honrath;P. Mahavadi;Richard Dodel;A. Dolga;Carsten Culmsee
在急性和慢性神经退行性疾病中，内质网ca2 +稳态的改变导致胞内ca2 +过度积累和延迟神经元细胞死亡。虽然我们最近的研究确定了SK通道对细胞内过量ca2 +积累的保护作用，但它们在内质网中的功能作用尚未阐明。我们在这里表明，SK2通道存在于神经元HT-22细胞的内质网膜中，并且CyPPA对SK2通道的阳性药理调节可以防止内质网应激源brefeldin A和tunicamycin诱导的细胞死亡。HT-22神经元的钙成像显示，在持续内质网应激过程中，细胞内ca2 +水平升高和内质网ca2 +负荷降低在很大程度上可以通过SK2通道激活来阻止。有趣的是，SK2通道激活减少了未折叠蛋白应答转录因子ATF4的数量，但进一步增强了CHOP的诱导。使用siRNA方法，我们证实了ATF4在内质网应激中的有害作用，而CHOP调节对于brefeldin a毒性和cyppa介导的保护都是必不可少的。CyPPA不能阻止SERCA抑制剂thapsigarin阻断ca2 +内流进入内质网所引起的细胞死亡。奎宁阻断K+/H+交换体的K+外排可抑制cyppa介导的神经保护，提示质子摄取和K+释放在SK通道介导的神经保护中起重要作用。我们的数据表明，内质网SK2通道的激活保留了内质网ca2 +的摄取和保留，这决定了在持续内质网应激导致进行性神经元死亡的情况下细胞的存活。
Alteration of endoplasmic reticulum (ER) Ca 2+ 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.