Pannaccione A, Boscia F, Scorziello A, Adornetto A, Castaldo P, Sirabella R, Taglialatela M, Di Renzo G F, Annunziato L
Division of Pharmacology, Department of Neuroscience, School of Medicine, University of Naples Federico II, Naples, Italy.
Mol Pharmacol. 2007 Sep;72(3):665-73. doi: 10.1124/mol.107.034868. Epub 2007 May 10.
The aim of the present study was to investigate whether K(V)3.4 channel subunits are involved in neuronal death induced by neurotoxic beta-amyloid peptides (Abeta). In particular, to test this hypothesis, three main questions were addressed: 1) whether the Abeta peptide can up-regulate both the transcription/translation and activity of K(V)3.4 channel subunit and its accessory subunit, MinK-related peptide 2 (MIRP2); 2) whether the increase in K(V)3.4 expression and activity can be mediated by the nuclear factor-kappaB (NF-kappaB) family of transcriptional factors; and 3) whether the specific inhibition of K(V)3.4 channel subunit reverts the Abeta peptide-induced neurodegeneration in hippocampal neurons and nerve growth factor (NGF)-differentiated PC-12 cells. We found that Abeta(1-42) treatment induced an increase in K(V)3.4 and MIRP2 transcripts and proteins, detected by reverse transcription-polymerase chain reaction and Western blot analysis, respectively, in NGF-differentiated PC-12 cells and hippocampal neurons. Patch-clamp experiments performed in whole-cell configuration revealed that the Abeta peptide caused an increase in I(A) current amplitude carried by K(V)3.4 channel subunits, as revealed by their specific blockade with blood depressing substance-I (BDS-I) in both hippocampal neurons and NGF-differentiated PC-12 cells. The inhibition of NF-kappaB nuclear translocation with the cell membrane-permeable peptide SN-50 prevented the increase in K(V)3.4 protein and transcript expression. In addition, the SN-50 peptide was able to block Abeta(1-42)-induced increase in K(V)3.4 K(+) currents and to prevent cell death caused by Abeta(1-42) exposure. Finally, BDS-I produced a similar neuroprotective effect by inhibiting the increase in K(V)3.4 expression. As a whole, our data indicate that K(V)3.4 channels could be a novel target for Alzheimer's disease pharmacological therapy.
本研究的目的是调查K(V)3.4通道亚基是否参与神经毒性β-淀粉样肽（Aβ）诱导的神经元死亡。具体而言，为验证这一假设，研究提出了三个主要问题：1）Aβ肽是否能上调K(V)3.4通道亚基及其辅助亚基MinK相关肽2（MIRP2）的转录/翻译及活性；2）K(V)3.4表达和活性的增加是否可由转录因子核因子-κB（NF-κB）家族介导；3）K(V)3.4通道亚基的特异性抑制是否能逆转Aβ肽诱导的海马神经元和神经生长因子（NGF）分化的PC-12细胞中的神经退行性变。我们发现，通过逆转录-聚合酶链反应和蛋白质印迹分析分别检测，Aβ(1-42)处理可使NGF分化的PC-12细胞和海马神经元中K(V)3.4和MIRP2的转录本及蛋白增加。在全细胞模式下进行的膜片钳实验显示，Aβ肽可使K(V)3.4通道亚基携带的I(A)电流幅度增加，这在海马神经元和NGF分化的PC-12细胞中均通过血降压物质-I（BDS-I）对其特异性阻断得以证实。用细胞膜可渗透肽SN-50抑制NF-κB核转位可防止K(V)3.4蛋白和转录本表达增加。此外，SN-50肽能够阻断Aβ(1-42)诱导的K(V)3.4钾电流增加，并防止Aβ(1-42)暴露引起的细胞死亡。最后，BDS-I通过抑制K(V)3.4表达增加产生了类似的神经保护作用。总体而言，我们的数据表明K(V)3.4通道可能是阿尔茨海默病药物治疗的新靶点。
