Busch S, Wieland T, Esche H, Jakobs K H, Siffert W
Institut für Pharmakologie, Universität GH Essen, Germany.
J Biol Chem. 1995 Jul 28;270(30):17898-901. doi: 10.1074/jbc.270.30.17898.
We have characterized the regulation of the endogenous Na+/H+ exchanger in Xenopus laevis oocytes by G proteins and protein kinases by measuring the ethylisopropylamiloride-sensitive Li+ uptake. Injection of oocytes with the stable GTP analog GTP gamma S stimulated Li+ uptake up to almost 4-fold, an effect blocked by coinjection with the GDP analog, guanyl-5'-yl thiophosphate. Injection into oocytes of beta gamma subunits of the heterotrimeric G protein transducin enhanced Li+ uptake by about 3-fold. This stimulation was blocked by transducin alpha subunits, which by themselves did not influence Li+ uptake. Using various activators and inhibitors of protein kinases, it is demonstrated that the X. laevis oocyte Na+/H+ antiporter can be stimulated by activation of both protein kinase A and C. Stimulation of Na+/H+ exchanger activity by GTP gamma S but not that induced by transducin beta gamma subunits was blocked by the protein kinase A inhibitor H-89. On the other hand, transducin beta gamma subunit-stimulated activity was prevented by the protein kinase C inhibitor, calphostin C. The non-selective protein kinase inhibitor H-7 blocked both GTP gamma S- and transducin beta gamma subunit-stimulated Na+/H+ exchanger activity. The results suggest that the Na+/H+ exchanger of X. laevis oocytes can be activated by G proteins and that this activation is not direct but mediated by protein kinase A- and/or protein kinase C-dependent pathways.
我们通过测量乙基异丙基氨氯地平敏感的锂离子摄取，对非洲爪蟾卵母细胞中G蛋白和蛋白激酶对内源性钠氢交换体的调节进行了表征。向卵母细胞注射稳定的GTP类似物GTPγS可使锂离子摄取刺激近4倍，与GDP类似物鸟苷-5'-硫代磷酸共注射可阻断此效应。向卵母细胞注射异三聚体G蛋白转导素的βγ亚基可使锂离子摄取增强约3倍。这种刺激被转导素α亚基阻断，而转导素α亚基本身并不影响锂离子摄取。使用各种蛋白激酶激活剂和抑制剂表明，非洲爪蟾卵母细胞钠氢反向转运体可被蛋白激酶A和C的激活所刺激。蛋白激酶A抑制剂H-89可阻断GTPγS对钠氢交换体活性的刺激，但不能阻断转导素βγ亚基诱导的刺激。另一方面，蛋白激酶C抑制剂钙泊三醇可阻止转导素βγ亚基刺激的活性。非选择性蛋白激酶抑制剂H-7可阻断GTPγS和转导素βγ亚基刺激的钠氢交换体活性。结果表明，非洲爪蟾卵母细胞的钠氢交换体可被G蛋白激活，且这种激活不是直接的，而是由蛋白激酶A和/或蛋白激酶C依赖性途径介导的。
