APOPTOSIS IN AN INTERLEUKIN-2-DEPENDENT CYTOTOXIC T-LYMPHOCYTE CELL-LINE IS ASSOCIATED WITH INTRACELLULAR ACIDIFICATION - ROLE OF THE NA+/H+-ANTIPORT
APOPTOSIS IN AN INTERLEUKIN-2-DEPENDENT CYTOTOXIC T-LYMPHOCYTE CELL-LINE IS ASSOCIATED WITH INTRACELLULAR ACIDIFICATION - ROLE OF THE NA+/H+-ANTIPORT
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DOI：
10.1074/jbc.270.7.3203
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发表时间：
1995-02-17
影响因子：
4.8
通讯作者：
EASTMAN, A
中科院分区：
文献类型：
--
作者：
LI, JF;EASTMAN, A
细胞凋亡是一种与DNA断裂和染色质凝聚相关的细胞死亡形式。我们最近发现细胞内酸化发生在细胞毒性损伤后的细胞凋亡过程中。目前的研究旨在确定细胞内酸化是否更普遍地与细胞凋亡相关，特别是在生长因子戒断模型中。白细胞介素-2退出后，CTLL-2细胞在细胞周期的G(1)期积累，并在12 h左右开始分裂DNA，同时pH降低，Ca2+增加。Ca2+螯合不抑制DNA消化，而钙离子载体孵育既防止酸化和DNA消化。酸化而不是增加Ca2+与细胞凋亡相关。酸化的细胞代表了一个离散的群体，高达0.7 pH单位低于正常。酸化程度取决于胞外pH值；当pH值高于6.3时，细胞内pH值明显低于胞外pH值，而当pH值低于6.3时，细胞仍能调节自身的pH值。在这种酸性条件下，Na+/H+-反港的抑制阻止了凋亡细胞对胞内pH的调节。这些结果表明，凋亡细胞保留了一个功能性的反端口，但其设定点发生了变化。已知许多存活因子磷酸化并激活反端口，因此凋亡可能与去磷酸化有关。虽然酸化总是发生在细胞凋亡过程中，但维持细胞内pH高于7.2并不能阻止细胞凋亡，这表明酸性pH不是细胞凋亡所必需的。我们假设细胞凋亡的其他关键调节因子必须服从去磷酸化。
Apoptosis is a form of cell death associated with DNA fragmentation and chromatin condensation. We recently established that intracellular acidification occurred during apoptosis following cytotoxic insult. The current studies were designed to determine whether intracellular acidification was more generally associated with apoptosis, specifically in a model of growth factor withdrawal. Upon withdrawal of interleukin-2, CTLL-2 cells accumulated in the G(1) phase of the cell cycle and started to fragment their DNA around 12 h concurrent with both decreased pH and increased Ca2+. Chelation of Ca2+ did not inhibit DNA digestion, whereas incubation with a calcium ionophore pre vented both acidification and DNA digestion Hence,. acidification rather than increased Ca2+ was associated with apoptosis. The acidified cells represented a discrete population up to 0.7 pH units below normal. The extent of acidification depended upon the extracellular pH; above pH 6.3, intracellular pH was significantly below extracellular pH, whereas below pH 6.3, the cells still regulated their pH. inhibition of the Na+/H+-antiport prevented the apoptotic cells from regulating their intracellular pH under these acidic conditions. These results demonstrate that apoptotic cells retain a functional antiport but that its set-point has changed, Many survival factors are known to phosphorylate and activate the antiport, hence apoptosis is likely to be associated with dephosphorylation. Although acidification always occurred during apoptosis, maintaining intracellular pH above 7.2 did not prevent apoptosis, suggesting that an acid pH is not essential for apoptosis, We hypothesize that other critical regulators of apoptosis must be subject to dephosphorylation.