Bano Daniele, Nicotera Pierluigi
Medical Research Council Toxicology Unit, Hodgkin Building, University of Leicester, Leicester, UK.
Stroke. 2007 Feb;38(2 Suppl):674-6. doi: 10.1161/01.STR.0000256294.46009.29.
Although Ca(2+) signals are necessary for cell communication and survival, abnormal cellular Ca(2+) load can trigger different cell death programs. Ca(2+) mediates cell death by activating proteases (ie, calpains), by reinforcing signals leading to caspase activation or by triggering other catabolic processes mediated by lipases and nucleases. Failure in the clearance of excitatory amino acid is a critical determinant of neuronal loss in the ischemic brain. Glutamate activates glutamate-ionotropic receptors at synaptic and extra-synaptic sites, causing prolonged neuronal depolarization and triggering deregulation of cellular ion homeostasis, mainly intracellular calcium and sodium. The mechanisms leading to the sustained calcium deregulation in excitotoxic conditions are only in part elucidated. Recently, we have shown that calpains mediate the inhibition of calcium efflux in primary dissociated neurons challenged with excitotoxic glutamate concentrations. Calpains cleave the sodium-calcium exchanger (NCX) and inhibit its capability to remove calcium accumulated as a consequence of the excitotoxic stimulus. Our findings highlight the link between calcium-dependent proteases, calcium overload and neuronal degeneration after an excitotoxic insult.
尽管钙离子信号对于细胞通讯和存活是必需的,但细胞内异常的钙离子负荷可触发不同的细胞死亡程序。钙离子通过激活蛋白酶(如钙蛋白酶)、增强导致半胱天冬酶激活的信号或触发由脂肪酶和核酸酶介导的其他分解代谢过程来介导细胞死亡。兴奋性氨基酸清除失败是缺血性脑神经元丢失的关键决定因素。谷氨酸在突触和突触外位点激活离子型谷氨酸受体,导致神经元长时间去极化,并引发细胞离子稳态失调,主要是细胞内钙和钠的失调。兴奋性毒性条件下导致持续钙失调的机制仅部分得到阐明。最近,我们发现钙蛋白酶在受到兴奋性毒性谷氨酸浓度刺激的原代解离神经元中介导钙外流的抑制。钙蛋白酶切割钠钙交换体(NCX)并抑制其清除因兴奋性毒性刺激而积累的钙的能力。我们的研究结果突出了兴奋性毒性损伤后钙依赖性蛋白酶、钙超载与神经元变性之间的联系。
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