Effects of nicotinic acetylcholine receptor overexpression in neuronal cells.

转染α7nAChR基因的PC12细胞在不受激活性刺激的情况下，细胞内磷酸化细胞外信号调节蛋白(ERK)的持续表达与α7亚单位蛋白的表达一样显著。高表达α7nAChR的PC12细胞迁移能力强，突起生长明显，贴壁，表面N-钙粘附素表达增加，但增殖活性低。细胞周期分布检测显示，过表达α7nAChR的PC12细胞中G2期细胞比例增加。这些结果提示，α7nAChR的过度表达诱导了ERK的持续激活，这可能促进了神经元特异性CDK的功能和分化样转化。α7nAChR的充分表达所必需的细胞骨架机制可能与促进轴突生长的ERK和CDK信号有关，而它们在老年人中的下降可能阻止了…为了探讨蛋白激酶Cδ(PKCδ)在血管紧张素II诱导的缺氧性神经元损伤易化机制中的作用，以及AT1受体拮抗剂坎地沙坦能否抑制这些机制，我们在低氧/复氧条件下对PC12细胞进行了体外实验。血管紧张素Ⅱ上调缺氧前6 4 3位磷酸化的PKCδ的基础表达水平，促进其催化片段的裂解，促进缺氧后δ的断裂。坎地沙坦可抑制PKCDNA的磷酸化和裂解，并抑制血管紧张素II诱导的δ断裂。在表达δ突变体的PC12细胞中，无论有没有血管紧张素Ⅱ存在，都能显著抑制δ的断裂。这些结果表明，血管紧张素II诱导的缺氧条件下DNA断裂的易化是由PKC AT1介导的，其机制可被坎地沙坦介导的AT1受体阻断所抑制。较少

PC12 cells transfected with the α7nAChR cDNA, independent of agonistic stimulation, exhibited to start the sustained expression of phospho-extracellular-signal-regulated kinases (ERKs) as immediately as expression of α 7 subunit protein after transfection. PC12 cells over-expressing α7nAChR showed high migration ability, marked neurite outgrowth, adherence to the culture dish and an increase in expression of surface N-cadherin, whereas their proliferation activity was low. Examination of cell cycle distribution showed an increase in the proportion of G2-phase cells in PC12 cells over-expressing α 7nAChR. These findings suggest that, over-expression of α7nAChR induces sustained activation of ERK, which probably promotes the functions of neuron-specific Cdks and differentiation-like transformation. The cytoskeletal machinery necessary for sufficient expression of α7nAChR may have some links to ERK and Cdk signals promoting neurite outgrowth, and their declines in the elderly may deterior … More ate neuronal plasticity.To investigate the role of protein kinase Cδ (PKCδ) in angiotensin II -induced facilitation mechanisms of hypoxic neuronal damage and whether candesartan, an AT1 receptor antagonist, can suppress these mechanisms, we performed in vitro experiments using PC12 cells under hypoxic/reoxygenation conditions. Angiotensin II increased the basal expression level of PKCδ phosphorylated at Ser643 before hypoxia, promoted the cleavage of PKC δ to its catalytic fragment, and fostered the progression of DNA fragmentation after hypoxia. Candesartan inhibited both phosphorylation and cleavage of PKCδ and suppressed the angiotensin II -induced facilitation of DNA fragmentation. In PC12 cells expressing the ATP-binding mutant of PKCδ acting as a dominant-negative protein, DNA fragmentation was markedly suppressed regardless of the presence of angiotensin II. These findings suggest that angiotensin II -induced facilitation of DNA fragmentation under hypoxic conditions is mediated by PKCδ, and the mechanisms can be suppressed by the candesartan mediated blockade of the AT1 receptor. Less