Cheng X J, Höög J O, Nairn A C, Greengard P, Aperia A
Department of Woman and Child Health, Karolinska Institute, Stockholm, Sweden.
Am J Physiol. 1997 Dec;273(6):C1981-6. doi: 10.1152/ajpcell.1997.273.6.C1981.
We have previously shown that the rat Na(+)-K(+)-ATPase alpha 1-isoform is phosphorylated at Ser-943 by protein kinase A (PKA) and at Ser-23 by protein kinase C (PKC), which in both cases results in inhibition of enzyme activity. We now present evidence that suggests that the phosphorylation of Ser-943 by PKA modulates the response of Na(+)-K(+)-ATPase to PKC. Rat Na(+)-K(+)-ATPase alpha 1 or a mutant in which Ser-943 was changed to Ala-943 was stably expressed in COS cells. The inhibition of enzyme activity measured in response to treatment with the phorbol ester, phorbol 12,13-dibutyrate (PDBu; 10(-6) M), was significantly reduced in the cells expressing the Ala-943 mutant compared with that observed in cells expressing wild-type enzyme. In contrast, for cells expressing Na(+)-K(+)-ATPase alpha 1 in which Ser-943 was mutated to Asp-943, the effect of PDBu was slightly enhanced. The PDBu-induced inhibition was not mediated by activation of the adenosine 3',5'-cyclic monophosphate/PKA system and was not achieved via direct phosphorylation of Ser-943. Sp-5,6-DCI-cBIMPS, a specific PKA activator, increased the phosphorylation of Ser-943, and this was associated with an enhanced response to PDBu. Thus the effect of PKC on rat Na(+)-K(+)-ATPase alpha 1 is determined not only by the activity of PKC but also by the state of phosphorylation of Ser-943.
我们之前已经表明，大鼠Na(+)-K(+)-ATP酶α1同工型在丝氨酸943位点被蛋白激酶A（PKA）磷酸化，在丝氨酸23位点被蛋白激酶C（PKC）磷酸化，这两种情况均导致酶活性受到抑制。我们现在提供的证据表明，PKA对丝氨酸943的磷酸化调节了Na(+)-K(+)-ATP酶对PKC的反应。大鼠Na(+)-K(+)-ATP酶α1或丝氨酸943被替换为丙氨酸943的突变体在COS细胞中稳定表达。与表达野生型酶的细胞相比，在用佛波酯佛波醇12,13-二丁酸酯（PDBu；10(-6) M）处理后，表达丙氨酸943突变体的细胞中测得的酶活性抑制作用显著降低。相反，对于表达丝氨酸943突变为天冬氨酸943的Na(+)-K(+)-ATP酶α1的细胞，PDBu的作用略有增强。PDBu诱导的抑制作用不是由腺苷3',5'-环磷酸/PKA系统的激活介导的，也不是通过丝氨酸943的直接磷酸化实现的。特异性PKA激活剂Sp-5,6-DCI-cBIMPS增加了丝氨酸943的磷酸化，这与对PDBu的反应增强有关。因此，PKC对大鼠Na(+)-K(+)-ATP酶α1的作用不仅取决于PKC的活性，还取决于丝氨酸943的磷酸化状态。
