Yung Hong Wa, Tolkovsky Aviva M
Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
J Neurochem. 2003 Sep;86(5):1281-8. doi: 10.1046/j.1471-4159.2003.01946.x.
We have examined the relationship between adenosine triphosphate (ATP) concentration and loss of maintenance of kinase-signalling cascades in primary cortical astrocytes during oxygen-glucose deprivation (OGD) as this may constitute an irreversible step that commits astrocytes to cell death. We report that the phosphorylation of Akt, ERK, JNK and p38 kinases, whose activities depend on serine, threonine and tyrosine phosphorylation, were all increased during OGD. All these phosphorylations were reduced to below detection limits when ATP levels were less than 10% of normal levels. Using ERK and Akt as representative examples, we show that this erasure is not irreversible as both ERK and Akt phosphorylations can be partially restored by addition of glucose under anoxic conditions. We further investigated whether OGD caused any change in phosphatase activity. The PP1/PP2A phosphatase inhibitors okadaic acid and caliculyn A, but not cyclosporine A, delayed the removal of ERK and Akt phosphorylation under OGD. By comparing the extent of phosphorylation increase under OGD and normoxic conditions, we calculate that phosphatase activity was increased by approximately 3.6-fold during OGD. These data show that ATP levels control an important checkpoint in kinase function, and that ATP levels may need to be considered when studies of kinase function in relation to OGD are conducted.
我们研究了氧糖剥夺（OGD）期间原代皮质星形胶质细胞中三磷酸腺苷（ATP）浓度与激酶信号级联维持丧失之间的关系，因为这可能构成星形胶质细胞走向细胞死亡的一个不可逆步骤。我们报告称，Akt、ERK、JNK和p38激酶的磷酸化（其活性依赖于丝氨酸、苏氨酸和酪氨酸磷酸化）在OGD期间均增加。当ATP水平低于正常水平的10%时，所有这些磷酸化都降低到检测限以下。以ERK和Akt为例，我们表明这种消除并非不可逆，因为在缺氧条件下添加葡萄糖可以部分恢复ERK和Akt的磷酸化。我们进一步研究了OGD是否会导致磷酸酶活性发生任何变化。PP1/PP2A磷酸酶抑制剂冈田酸和加利林A，但不是环孢素A，延迟了OGD条件下ERK和Akt磷酸化的去除。通过比较OGD和常氧条件下磷酸化增加的程度，我们计算出OGD期间磷酸酶活性增加了约3.6倍。这些数据表明，ATP水平控制着激酶功能中的一个重要检查点，并且在进行与OGD相关的激酶功能研究时可能需要考虑ATP水平。
