Iyirhiaro Grace O, Im Doo Soon, Boonying Wassamon, Callaghan Steve M, During Matthew J, Slack Ruth S, Park David S
University of Ottawa Brain and Mind Research Institute, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada, and.
Department of Molecular Virology, Immunology and Medical Genetics, and Neurological Surgery, College of Medicine, The Ohio State University, Columbus, Ohio 43210.
J Neurosci. 2017 Jul 12;37(28):6729-6740. doi: 10.1523/JNEUROSCI.3017-16.2017. Epub 2017 Jun 12.
Dysregulation of cell cycle machinery is implicated in a number of neuronal death contexts, including stroke. Increasing evidence suggests that cyclin-dependent kinases (Cdks) are inappropriately activated in mature neurons under ischemic stress conditions. We previously demonstrated a functional role for the cyclin D1/Cdk4/pRb (retinoblastoma tumor suppressor protein) pathway in delayed neuronal death induced by ischemia. However, the molecular signals leading to cyclin D/Cdk4/pRb activation following ischemic insult are presently not clear. Here, we investigate the cell division cycle 25 (Cdc25) dual-specificity phosphatases as potential upstream regulators of ischemic neuronal death and Cdk4 activation. We show that a pharmacologic inhibitor of Cdc25 family members (A, B, and C) protects mouse primary neurons from hypoxia-induced delayed death. The major contributor to the death process appears to be Cdc25A. shRNA-mediated knockdown of Cdc25A protects neurons in a delayed model of hypoxia-induced death Similar results were observed following global ischemia in the rat. In contrast, neurons singly or doubly deficient for Cdc25B/C were not significantly protective. We show that Cdc25A activity, but not level, is upregulated following hypoxia and global ischemic insult Finally, we show that shRNA targeting Cdc25A blocks Ser795 pRb phosphorylation. Overall, our results indicate a role for Cdc25A in delayed neuronal death mediated by ischemia. A major challenge in stroke is finding an effective neuroprotective strategy to treat cerebral ischemic injury. Cdc25 family member A (Cdc25A) is a phosphatase normally activated during cell division in proliferating cells. We found that Cdc25A is activated in neurons undergoing ischemic stress mediated by hypoxia and global cerebral ischemia in rats We show that pharmacologic or genetic inhibition of Cdc25A activity protects neurons from delayed death and Downregulation of Cdc25A led to reduction in retinoblastoma tumor suppressor protein (pRb) phosphorylation. An increase in pRb phosphorylation has been previously linked to ischemic neuronal death. Our results identify Cdc25A as a potential target for neuroprotectant strategy for the treatment of delayed ischemic neuronal death.
细胞周期机制的失调与包括中风在内的多种神经元死亡情况有关。越来越多的证据表明，在缺血应激条件下，成熟神经元中的细胞周期蛋白依赖性激酶（Cdks）会被不适当激活。我们之前证明了细胞周期蛋白D1/Cdk4/pRb（视网膜母细胞瘤肿瘤抑制蛋白）通路在缺血诱导的延迟性神经元死亡中具有功能性作用。然而，目前尚不清楚缺血性损伤后导致细胞周期蛋白D/Cdk4/pRb激活的分子信号。在这里，我们研究细胞分裂周期25（Cdc25）双特异性磷酸酶作为缺血性神经元死亡和Cdk4激活的潜在上游调节因子。我们发现，Cdc25家族成员（A、B和C）的一种药理抑制剂可保护小鼠原代神经元免受缺氧诱导的延迟性死亡。死亡过程的主要促成因素似乎是Cdc25A。shRNA介导的Cdc25A敲低可在缺氧诱导死亡的延迟模型中保护神经元。在大鼠全脑缺血后也观察到了类似结果。相比之下，Cdc25B/C单基因或双基因缺陷的神经元并没有显著的保护作用。我们发现，缺氧和全脑缺血性损伤后，Cdc25A的活性上调，但其水平并未上调。最后，我们发现靶向Cdc25A的shRNA可阻断Ser795 pRb磷酸化。总体而言，我们的结果表明Cdc25A在缺血介导的延迟性神经元死亡中发挥作用。中风的一个主要挑战是找到一种有效的神经保护策略来治疗脑缺血损伤。细胞分裂周期25家族成员A（Cdc25A）是一种通常在增殖细胞的细胞分裂过程中被激活的磷酸酶。我们发现，在经历缺氧介导的缺血应激和大鼠全脑缺血的神经元中，Cdc25A被激活。我们发现，对Cdc25A活性进行药理或基因抑制可保护神经元免于延迟性死亡，并且Cdc25A的下调导致视网膜母细胞瘤肿瘤抑制蛋白（pRb）磷酸化减少。pRb磷酸化增加先前已与缺血性神经元死亡相关联。我们的结果确定Cdc25A是治疗延迟性缺血性神经元死亡的神经保护策略的一个潜在靶点。
