Murray S L, Knowles A F
Department of Biology, Northeastern University, Boston, Massachusetts 02115.
J Cell Physiol. 1990 Jul;144(1):26-35. doi: 10.1002/jcp.1041440105.
The human hepatoma cell line (Li-7A) possesses a high concentration of epidermal growth factor (EGF) receptors and exhibits ectoATPase activity in the presence of either MgATP or CaATP (Knowles: J. Cell. Physiol., 134:109-116, 1988). Growth for 96 hours in the presence of both EGF and cholera toxin or another cyclic AMP elevating agent induced an ectoATPase activity which was more active with CaATP and resistant to inhibition by the sulfydryl reagent, p-chloromercuriphenylsulfonate (pCMPS) (Knowles: Arch. Biochem. Biophys., 263: 264-271, 1988). In contrast, treatment of cells with butyrate, a short chain organic acid which can be derived from the analogue, dibutyryl cyclic AMP, resulted in a 4-7-fold increase of an ectoATPase which was more active with MgATP and highly sensitive to pCMPS inhibition. Maximal induction by butyrate required 48 hours and was dependent on butyrate concentration, but was independent of EGF and cyclic AMP elevating agents. Of six organic acids tested, butyrate was most effective in the induction of the ectoMg2(+)-ATPase. The increase in the ectoMg2(+)-ATPase activity could be prevented with actinomycin D and cycloheximide, indicating that both transcription and translation were necessary for induction. In addition to the induction of the ectoMg2(+)-ATPase, butyrate induced alkaline phosphatase activity, but had no effect on a third ectoenzyme 5'-nucleotidase. These data further support our proposal that two distinct ectoATPases exist in the plasma membrane of Li-7A hepatoma cells.
人肝癌细胞系（Li - 7A）具有高浓度的表皮生长因子（EGF）受体，并且在存在MgATP或CaATP的情况下表现出胞外ATP酶活性（诺尔斯：《细胞生理学杂志》，134:109 - 116，1988年）。在EGF和霍乱毒素或另一种环磷酸腺苷升高剂存在的情况下培养96小时可诱导出一种胞外ATP酶活性，该活性对CaATP更具活性，并且对巯基试剂对氯汞苯磺酸盐（pCMPS）的抑制具有抗性（诺尔斯：《生物化学与生物物理学文献》，263:264 - 271，1988年）。相比之下，用丁酸盐（一种可从类似物二丁酰环磷酸腺苷衍生而来的短链有机酸）处理细胞，导致一种对MgATP更具活性且对pCMPS抑制高度敏感的胞外ATP酶增加了4至7倍。丁酸盐的最大诱导作用需要48小时，并且依赖于丁酸盐浓度，但与EGF和环磷酸腺苷升高剂无关。在所测试的六种有机酸中，丁酸盐在诱导胞外Mg2(+) - ATP酶方面最有效。胞外Mg2(+) - ATP酶活性的增加可以用放线菌素D和环己酰亚胺阻止，这表明转录和翻译对于诱导都是必需的。除了诱导胞外Mg2(+) - ATP酶外，丁酸盐还诱导碱性磷酸酶活性，但对第三种胞外酶5'-核苷酸酶没有影响。这些数据进一步支持了我们的提议，即Li - 7A肝癌细胞质膜中存在两种不同的胞外ATP酶。
