Hwang Jung Jin, Park Mi-Ha, Koh Jae-Young
NRL Neural Injury Research Center, University of Ulsan College of Medicine, Seoul, Korea.
J Neurosci Res. 2007 Aug 1;85(10):2160-6. doi: 10.1002/jnr.21350.
Copper (Cu) is an endogenous metal that is physiologically essential in the brain and that, like zinc (Zn), may be synaptically released in certain regions. Previously, we demonstrated that Zn activates TrkB in cultured cortical neurons in a metalloproteinase (MP)-dependent manner. To determine whether Cu has similar properties, we exposed cortical cultures for 15 min to various metals and performed Western blots to detect tyrosine-phosphorylated TrkB (p-Trk). Whereas Cd, Mn, Fe(II), and Fe(III) had no effect on the level of p-Trk, 10 microM of Cu in phosphate-containing (Hanks' balanced salt solution) or 10 nM in phosphate-lacking salt solution (control salt solution), increased levels of p-Trk. Cu also activated extracellular signal-regulated kinase 1/2 and Src tyrosine kinase, signaling molecules activated downstream of TrkB. Cu decreased levels of probrain-derived neurotrophic factor (pro-BDNF) in cells but increased levels of pro- and mature BDNF in the media. Addition of MP inhibitors completely blocked the Cu-induced increases in pro-BDNF and BDNF as well as TrkB activation, indicating that MP mediates most of the Cu effect. Furthermore, Cu increased the activity of matrix metalloproteinase 2 (MMP2) and MMP9 in cortical neurons. These findings indicate that, like Zn, Cu activates MPs, releases pro-BDNF from cells, and phosphorylates TrsB. Because Cu, like Zn, is released in certain brain areas with neuronal activity, metal-triggered TrkB activation may occur in both Cu- and Zn-containing synapses.
铜（Cu）是一种内源性金属，在大脑中具有生理重要性，并且与锌（Zn）一样，可能在某些区域通过突触释放。此前，我们证明锌以金属蛋白酶（MP）依赖的方式激活培养的皮质神经元中的TrkB。为了确定铜是否具有类似特性，我们将皮质培养物暴露于各种金属15分钟，并进行蛋白质免疫印迹以检测酪氨酸磷酸化的TrkB（p-Trk）。虽然镉、锰、亚铁离子（Fe(II)）和铁离子（Fe(III)）对p-Trk水平没有影响，但在含磷酸盐的（汉克斯平衡盐溶液）中10微摩尔的铜或在无磷酸盐盐溶液（对照盐溶液）中10纳摩尔的铜，会增加p-Trk的水平。铜还激活细胞外信号调节激酶1/2和Src酪氨酸激酶，这些是在TrkB下游被激活的信号分子。铜降低了细胞中脑源性神经营养因子前体（pro-BDNF）的水平，但增加了培养基中pro-BDNF和成熟BDNF的水平。添加MP抑制剂完全阻断了铜诱导的pro-BDNF和BDNF增加以及TrkB激活，表明MP介导了铜的大部分作用。此外，铜增加了皮质神经元中基质金属蛋白酶2（MMP2）和MMP9的活性。这些发现表明，与锌一样，铜激活MPs，从细胞中释放pro-BDNF，并使TrsB磷酸化。由于铜与锌一样，在某些具有神经元活动的脑区释放，金属触发的TrkB激活可能发生在含铜和含锌的突触中。
