Protein phosphatases 1 and 2A promote Raf-1 activation by regulating 14-3-3 interactions
Protein phosphatases 1 and 2A promote Raf-1 activation by regulating 14-3-3 interactions
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DOI：
10.1038/sj.onc.1204526
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发表时间：
2001-07-05
期刊：
影响因子：
8
通讯作者：
Hancock, JF
中科院分区：
文献类型：
--
作者：
Jaumot, M;Hancock, JF
Raf-1 激活是一个复杂的过程，涉及质膜募集、磷酸化、蛋白质-蛋白质和脂质-蛋白质相互作用。我们现在表明，PP1 和 PP2A 丝氨酸-苏氨酸磷酸酶在 Ras 依赖性 Raf-1 激活中也具有积极作用，一般丝氨酸-苏氨酸磷酸酶抑制剂，如氟化钠、或 β-甘油磷酸盐和焦磷酸钠，或特定 PP1 和 PP2A 抑制剂，包括微囊藻毒素-LR、蛋白磷酸酶 2A 抑制剂 I-1 或蛋白磷酸酶抑制剂 2 均可在体外消除 H-Ras 和 K-Ras 依赖性 Raf-1 激活。 PP1 和 PP2A 的关键 Raf-1 目标残基是 S259。丝氨酸磷酸酶抑制剂阻断伴随 Raf-1 激活的 S259 去磷酸化，并且突变型 Raf259A 的 Ras 依赖性激活对丝氨酸磷酸酶抑制剂相对具有抵抗力。蔗糖梯度分析表明，丝氨酸磷酸酶抑制增加了与质膜相关的 14-3-3 和 Raf-1 的总量，并显着改变了 14-3-3 和 Raf-1 在不同质膜微域上的分布。这些观察结果表明，S259 的去磷酸化是 Ras 依赖性 Raf-1 激活的关键早期步骤，促进 14-3-3 置换。因此，抑制 PP1 和 PP2A 会导致 Raf-1/14-3-3 复合物在质膜上积聚，而无法被激活。
Raf-1 activation is a complex process which involves plasma membrane recruitment, phosphorylation, protein-protein and lipid-protein interactions, We now show that PP1 and PP2A serine-threonine phosphatases also have a positive role in Ras dependent Raf-1 activation, General serine-threonine phosphatase inhibitors such sodium fluoride, or beta-glycerophosphate and sodium pyrophosphate, or specific PP1 and PP2A inhibitors including microcystin-LR, protein phosphatase 2A inhibitor I-1 or protein phosphatase inhibitor 2 all abrogate H-Ras and K-Ras dependent Raf-1 activation in vitro. A critical Raf-1 target residue for PP1 and PP2A is S259. Serine phosphatase inhibitors block the dephosphorylation of S259, which accompanies Raf-1 activation, and Ras dependent activation of mutant Raf259A is relatively resistant to serine phosphatase inhibitors. Sucrose gradient analysis demonstrates that serine phosphatase inhibition increases the total amount of 14-3-3 and Raf-1 associated with the plasma membrane and significantly alters the distribution of 14-3-3 and Raf-1 across different plasma membrane microdomains, These observations suggest that dephosphorylation of S259 is a critical early step in Ras dependent Raf-1 activation which facilitates 14-3-3 displacement. Inhibition of PP1 and PP2A therefore causes plasma membrane accumulation of Raf-1/14-3-3 complexes which cannot be activated.