Pahlavani M A, Vargas D M
Geriatric Research, Education, and Clinical Center, South Texas Veterans Health Care System, Audie L. Murphy Veterans Hospital, San Antonio 78284, USA.
Mech Ageing Dev. 1999 Dec 7;112(1):59-74. doi: 10.1016/s0047-6374(99)00077-9.
We have previously shown that the DNA binding activity of the transcription factor NFAT which plays a predominant role in IL-2 transcription decreases with age. Because the transactivation (dephosphorylation and nuclear translocation) of the NFAT-c (cytoplasmic component of the NFAT complex) is mediated by the calcium/calmodulin-dependent phosphatase, calcineurin (CaN), and because Ca2+/calmodulin-dependent kinases (CaMK-II and IV/Gr) have been shown to play a critical role in calcium signaling in T cells, it was of interest to determine what effect aging has on the activation and the levels of these calcium regulating enzymes. The induction of calcineurin phosphatase activity, and CaMK-II and IV/Gr activities, were studied in splenic T cells isolated from Fischer 344 rats at 6, 15, and 24 months of age. In addition, the changes in the protein levels of these enzymes were measured by Western blot. The calcineurin phosphatase activity and CaMK-II and IV kinase activities were at a maximum after the cells were incubated with anti-CD3 antibody for 5-10 minutes. The induction of calcineurin activity by anti-CD3 and by calcium ionophore (A23187) declined 65 and 55%, respectively, between 6 and 24 months of age. The induction of CaMK-IV activity, but not CaMK-II activity by anti-CD3, was significantly less (by 54%) in T cells from old rats compared to T cells from young rats. The decline in the activation of these enzymes with age was not associated with changes in their corresponding protein levels. These results demonstrate that alterations in calcineurin phosphatase activity and CaMK-IV activity may contribute to the well-documented age-related decline in T cell function.
我们之前已经表明，在白细胞介素-2转录中起主要作用的转录因子NFAT的DNA结合活性会随着年龄的增长而降低。由于NFAT-c（NFAT复合物的细胞质成分）的反式激活（去磷酸化和核转位）是由钙/钙调蛋白依赖性磷酸酶钙调神经磷酸酶（CaN）介导的，并且由于钙/钙调蛋白依赖性激酶（CaMK-II和IV/Gr）已被证明在T细胞的钙信号传导中起关键作用，因此确定衰老对这些钙调节酶的激活和水平有何影响是很有意义的。我们研究了从6、15和24月龄的Fischer 344大鼠分离的脾T细胞中钙调神经磷酸酶磷酸酶活性以及CaMK-II和IV/Gr活性的诱导情况。此外，通过蛋白质免疫印迹法测量了这些酶的蛋白质水平变化。在用抗CD3抗体孵育细胞5 - 10分钟后，钙调神经磷酸酶磷酸酶活性以及CaMK-II和IV激酶活性达到最大值。在6至24月龄之间，抗CD3和钙离子载体（A23187）诱导的钙调神经磷酸酶活性分别下降了65%和55%。与年轻大鼠的T细胞相比，老年大鼠T细胞中抗CD3诱导的CaMK-IV活性（而非CaMK-II活性）显著降低（降低了54%）。这些酶的激活随年龄的下降与它们相应蛋白质水平的变化无关。这些结果表明，钙调神经磷酸酶磷酸酶活性和CaMK-IV活性的改变可能导致了文献记载的T细胞功能随年龄增长而下降。
