Kochhar A, Saitoh T, Zivin J A
Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla 92093.
Brain Res. 1991 Feb 22;542(1):141-6. doi: 10.1016/0006-8993(91)91008-o.
Calcium/calmodulin (Ca2+/CaM)-dependent protein phosphorylation was evaluated in a rabbit spinal cord ischemia model. One hour of ischemia reduced particulate (5% of control) and cytosolic (35% of control) Ca2+/CaM-dependent protein kinase activity significantly (p less than 0.01). In vitro phosphorylation of endogenous proteins by endogenous Ca2+/CaM-dependent protein kinase showed that phosphorylation of 14 particulate and 7 cytosolic proteins was stimulated in the presence of Ca2+/CaM in control tissue. However, after 1 hour of ischemia, Ca2+/CaM-dependent protein phosphorylation was virtually absent in the particulate fraction and significantly reduced in the cytosol. When equal amounts of control and ischemic tissue samples were combined and assayed, Ca2+/CaM-dependent protein kinase activity was 43% of control in particulate and 70% of control in cytosolic fractions. This suggests that reduced Ca2+/CaM-dependent protein phosphorylation is probably not due to the presence of an inhibitory activity in ischemic tissue. These results show that the Ca2+/CaM-dependent protein phosphorylation system is impaired after ischemia durations which cause irreversible damage. These altered phosphorylation reactions may play critical roles in mediating irreversible neurologic injury.
在兔脊髓缺血模型中评估了钙/钙调蛋白（Ca2+/CaM）依赖性蛋白磷酸化情况。1小时的缺血显著降低了微粒体（对照组的5%）和胞质（对照组的35%）中Ca2+/CaM依赖性蛋白激酶活性（p<0.01）。内源性Ca2+/CaM依赖性蛋白激酶对内源性蛋白的体外磷酸化显示，在对照组织中，Ca2+/CaM存在时，14种微粒体蛋白和7种胞质蛋白的磷酸化受到刺激。然而，缺血1小时后，微粒体部分几乎不存在Ca2+/CaM依赖性蛋白磷酸化，胞质中则显著减少。当将等量的对照组织和缺血组织样本混合并进行检测时，微粒体部分的Ca2+/CaM依赖性蛋白激酶活性为对照组的43%，胞质部分为对照组的70%。这表明Ca2+/CaM依赖性蛋白磷酸化减少可能不是由于缺血组织中存在抑制活性。这些结果表明，在导致不可逆损伤的缺血持续时间后，Ca2+/CaM依赖性蛋白磷酸化系统受损。这些改变的磷酸化反应可能在介导不可逆神经损伤中起关键作用。
