Laboratório de Estrutura e Regulação de Proteínas e ATPases, Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Brazil.
Arch Biochem Biophys. 2011 Jan 1;505(1):75-82. doi: 10.1016/j.abb.2010.09.017. Epub 2010 Sep 24.
FXYD2 is a regulatory peptide associated with the α-subunit of the kidney Na,K-ATPase. FXYD2 can be phosphorylated by PKA, and its phosphorylation activates Na,K-ATPase. Here we show that FXYD2 is phosphorylated by PKC (PKC-FXYD2-P), by PKA (PKA-FXYD2-P) or by PKA and PKC simultaneously (FXYD2-P(2)) modulating both the erythrocyte Na,K-ATPase and the plasma membrane Ca(2+)-ATPase (PMCA). In erythrocyte ghosts, the addition of PKA-FXYD2-P activated Na,K-ATPase by 80%, while non-phosphorylated FXYD2 (np) activated only 55%. The addition of np FXYD2 did not affect PMCA basal activity, but FXYD2-P(2) increased the basal PMCA activity by up to 200%. Calmodulin-activated PMCA activity was increased by np FXYD2 (3-fold) or FXYD2-P(2) (2.5-fold). However, PKC-FXYD2-P increased PMCA activity only by 50%. In contrast, when PMCA was treated with PKA-FXYD2-P, the ATPase activity was inhibited by 50%. The effect of all forms of FXYD2-P on calcium uptake from PMCA resembled the pattern observed in ATP hydrolysis. Our results suggest that the FXYD2 anchoring site could be conserved among the P-ATPase family permitting cross regulation. The effects of FXYD2 on calcium uptake and calcium-stimulated ATP hydrolysis suggest a novel role for FXYD2 on PMCA.
FXYD2 是一种与肾脏 Na,K-ATPaseα亚单位相关的调节肽。FXYD2 可被 PKA 磷酸化，其磷酸化可激活 Na,K-ATPase。在这里，我们表明 FXYD2 可被 PKC（PKC-FXYD2-P）、PKA（PKA-FXYD2-P）或 PKA 和 PKC 同时磷酸化（FXYD2-P(2)），从而调节红细胞 Na,K-ATPase 和质膜 Ca(2+)-ATPase（PMCA）。在红细胞胞浆中，PKA-FXYD2-P 的添加可使 Na,K-ATPase 活性增加 80%，而非磷酸化的 FXYD2（np）仅增加 55%。np FXYD2 的添加不会影响 PMCA 的基础活性，但 FXYD2-P(2)可将基础 PMCA 活性增加高达 200%。np FXYD2 或 FXYD2-P(2)可使钙调蛋白激活的 PMCA 活性增加 3 倍或 2.5 倍。然而，PKC-FXYD2-P 仅使 PMCA 活性增加 50%。相反，当 PMCA 用 PKA-FXYD2-P 处理时，ATPase 活性被抑制 50%。所有形式的 FXYD2-P 对 PMCA 中钙摄取的影响与在 ATP 水解中观察到的模式相似。我们的结果表明，FXYD2 锚定位点可能在 P-ATPase 家族中保守，允许交叉调节。FXYD2 对钙摄取和钙刺激的 ATP 水解的影响表明 FXYD2 在 PMCA 上具有新的作用。
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