Okadaic acid, a phosphatase inhibitor, induces activation and phosphorylation of the Na+/H+ antiport.
Okadaic acid, a phosphatase inhibitor, induces activation and phosphorylation of the Na+/H+ antiport.
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冈田酸是一种磷酸酶抑制剂，可诱导 Na /H 逆向转运的激活和磷酸化。
DOI：
10.1016/s0021-9258(18)98630-8
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发表时间：
1991
期刊：
影响因子：
--
通讯作者：
S. Grinstein
中科院分区：
文献类型：
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作者：
L. Bianchini;M. Woodside;C. Sardet;J. Pouysségur;A. Takai;S. Grinstein
我们确定了冈田酸（OA），一种有效的磷蛋白磷酸酶抑制剂，对大鼠胸腺淋巴细胞和人膀胱癌细胞的细胞内pH值（pHi）的影响。OA诱导了快速和持续的细胞质碱化。这种pHi升高是Na（+）依赖性的，并被阿米洛利的5，N-二取代类似物抑制，表明Na+/H+反向转运介导。如对其他刺激剂（如有丝分裂原和高渗激发）所述，OA对反向转运的激活可归因于其pHi依赖性的上移。因此，由磷酸酶抑制剂产生的碱化与诱导的碱化不相加。由OA激活的反向转运伴随着磷蛋白积累的显著增加，揭示了在其他未受刺激的细胞中存在活性蛋白激酶。我们认为，磷酸化的反向转运本身或辅助蛋白是负责激活Na+/H+交换的可能性。与这一观点一致，OA诱导的碱化在ATP耗竭的细胞中不存在。更重要的是，免疫沉淀实验表明，增加磷酸化的反向运输治疗OA。我们的结论是，抑制磷蛋白磷酸酶活性后，组成型活性激酶诱导激活的Na+/H+交换，可能是通过直接磷酸化的反向。
We determined the effect of okadaic acid (OA), a potent phosphoprotein phosphatase inhibitor, on the intracellular pH (pHi) of rat thymic lymphocytes and human bladder carcinoma cells. OA induced a rapid and sustained cytosolic alkalinization. This pHi increase was Na(+)-dependent and was inhibited by 5,N-disubstituted analogs of amiloride, indicating mediation by the Na+/H+ antiport. As described for other stimulants, such as mitogens and hypertonic challenge, activation of the antiport by OA is attributable to an upward shift in its pHi dependence. Accordingly, the alkalinization produced by the phosphatase inhibitor was not additive with that induced osmotically. Activation of the antiport by OA was accompanied by a marked increase in phosphoprotein accumulation, revealing the presence of active protein kinases in otherwise unstimulated cells. We considered the possibility that phosphorylation of the antiport itself or of an ancillary protein is responsible for activation of Na+/H+ exchange. Consistent with this notion, the alkalinization induced by OA was absent in ATP depleted cells. More importantly, immunoprecipitation experiments demonstrated increased phosphorylation of the antiport following treatment with OA. We conclude that, upon inhibition of phosphoprotein phosphatase activity, constitutively active kinases induce the activation of Na+/H+ exchange, possibly by direct phosphorylation of the antiport.