Folkerts Michael M, Parks Elizabeth A, Dedman John R, Kaetzel Marcia A, Lyeth Bruce G, Berman Robert F
Department of Neurological Surgery, University of California Davis, Davis, California 95616, USA.
J Neurotrauma. 2007 Apr;24(4):638-50. doi: 10.1089/neu.2006.0188.
Traumatic brain injury (TBI) can dramatically increase levels of intracellular calcium (Ca(2+)). One consequence of increased Ca(2+) would be altered activity and function of calcium-regulated proteins, including calcium-calmodulin-dependent protein kinase II (CaMKII), which is autophosphorylated on Thr(286)(pCaMKII(286)) in the presence of calcium and calmodulin. Therefore, we hypothesized that TBI would result in increased levels of pCaMKII(286), and that such increases would occur early after injury in brain regions known to be damaged following lateral fluid percussion TBI (i.e., hippocampus and cortex). In order to test this hypothesis, immunostaining of CaMKII was examined in rat hippocampus and cortex after lateral fluid percussion (LFP) injury using an antibody directed against pCaMKII(286). LFP injury produced a marked increase in pCaMKII(286) immunostaining in the hippocampus and overlying cortex 30 min after TBI. The pattern of increased immunostaining was uneven, and unexpectedly absent in some hippocampal CA3 pyramidal neurons. This suggests that phosphatase activity may also increase following TBI, resulting in dephosphorylation of pCaMKII(286) in subpopulations of CA3 pyramidal neurons. Western blotting confirmed a rapid increase in levels of pCaMKII(286) at 10 and 30 min after brain injury, and that it was transient and no longer significantly elevated when examined at 3, 8, and 24 h. These results demonstrate that TBI alters the autophosphorylation state of CaMKII, an important neuronal regulator of critical cell functions, including enzyme activities, cell structure, gene expression, and neuronal plasticity, and provide a molecular mechanism that is likely to contribute to cell injury and impaired plasticity after TBI.
创伤性脑损伤（TBI）可显著提高细胞内钙（Ca(2+)）水平。Ca(2+)升高的一个后果是钙调节蛋白的活性和功能发生改变，包括钙调蛋白依赖性蛋白激酶II（CaMKII），其在钙和钙调蛋白存在的情况下在苏氨酸286（pCaMKII(286)）位点发生自身磷酸化。因此，我们推测TBI会导致pCaMKII(286)水平升高，且这种升高会在侧方流体冲击性TBI（即海马体和皮质）后已知受损的脑区损伤后早期出现。为了验证这一假设，使用针对pCaMKII(286)的抗体，对侧方流体冲击（LFP）损伤后的大鼠海马体和皮质进行CaMKII免疫染色检查。TBI后30分钟，LFP损伤使海马体和覆盖皮质中的pCaMKII(286)免疫染色显著增加。免疫染色增加的模式不均匀，并且在一些海马CA3锥体神经元中意外缺失。这表明TBI后磷酸酶活性也可能增加，导致CA3锥体神经元亚群中的pCaMKII(286)去磷酸化。蛋白质印迹法证实脑损伤后10分钟和30分钟时pCaMKII(286)水平迅速升高，且这种升高是短暂的，在3小时、8小时和24小时检查时不再显著升高。这些结果表明，TBI改变了CaMKII的自身磷酸化状态，CaMKII是细胞关键功能（包括酶活性、细胞结构、基因表达和神经元可塑性）的重要神经元调节因子，并提供了一种可能导致TBI后细胞损伤和可塑性受损的分子机制。
