Proapoptotic kinase MST2 coordinates signaling crosstalk between RASSF1A, Raf-1, and Akt.
Proapoptotic kinase MST2 coordinates signaling crosstalk between RASSF1A, Raf-1, and Akt.
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DOI：
10.1158/0008-5472.can-09-3147
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发表时间：
2010-02-01
期刊：
影响因子：
11.2
通讯作者：
Kolch W
中科院分区：
文献类型：
--
作者：
Romano D;Matallanas D;Weitsman G;Preisinger C;Ng T;Kolch W
哺乳动物不育20 样激酶 (MST1/2) 参与应激诱导的细胞凋亡信号传导。 MST2 受到 Raf-1 结合的抑制，其激活需要从 Raf-1 解离并与 RASSF1A 肿瘤抑制蛋白结合。在这里，我们研究了促生存磷酸肌醇 3 激酶 (PI3K)-Akt 通路对 MST2 的调节。 Akt 响应有丝分裂原、致癌 Ras 表达或肿瘤抑制磷酸酶和 10 号染色体上缺失的张力蛋白同源物 (PTEN) 的消耗，使 MST2 磷酸化。我们在 MST2 中鉴定了两个 Akt 磷酸化位点（T117 和 T384）。这些位点的突变单独降低了磷酸化，而双重突变则消除了磷酸化。这些突变，尤其是双突变，抑制了 MST2 与 Raf-1 的相互作用，但增强了与 RASSF1A 的结合，导致下游应激信号通路（JNK 和 p38 MAPK）的更高激活和细胞凋亡。生化和原位 FLIM 实验揭示了双重抑制机制。 MST2 的 Akt 磷酸化 (i) 阻断与 RASSF1A 的结合并促进与 Raf-1 的抑制复合物隔离； (ii) 防止 MST2 同二聚化，这对于 MST2 激活至关重要。我们的结果进一步表明，Raf-1-MST2 复合物的解离是促有丝分裂信号传导的一部分，从而将增殖诱导与细胞凋亡风险联系起来。选择性偶联 PI3K 或 Raf-1 的 Ras 效应结构域突变体的结果表明，Akt 激活对于消除响应有丝分裂刺激的 MST2 激活是必要的。因此，MST2 充当整合 Raf-1 和 Akt 途径生物输出的枢纽。
Mammalian sterile20-like kinases (MST1/2) are involved in stress-induced apoptosis signalling. MST2 is inhibited by Raf-1 binding, and its activation requires dissociation from Raf-1 and binding to the RASSF1A tumour suppressor protein. Here, we have investigated the regulation of MST2 by the pro-survival phosphoinositide-3 kinase (PI3K)-Akt pathway. Akt phosphorylates MST2 in response to mitogens, oncogenic Ras expression or depletion of the tumour suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN). We identified two Akt phosphorylation sites (T117 and T384) in MST2. Mutation of these sites individually reduced phosphorylation, while the double mutation abolished it. These mutations, especially the double mutation, inhibited MST2 interactions with Raf-1, but enhanced binding to RASSF1A resulting in higher activation of downstream stress signalling pathways (JNK and p38 MAPK) and apoptosis. Biochemical and in situ FLIM experiments revealed a dual mechanism of inhibition. Akt phosphorylation of MST2 (i) blocks binding to RASSF1A and promotes sequestration into the inhibitory complex with Raf-1; and (ii) prevents MST2 homo-dimerisation which is essential for MST2 activation. Our results further show that the dissociation of the Raf-1-MST2 complex is part of mitogenic signalling, thereby linking induction of proliferation with the risk of apoptosis. Results with Ras effector domain mutants that selectively couple to either PI3K or Raf-1 show that Akt activation is necessary to abrogate MST2 activation in response to mitogenic stimulation. Thus, MST2 serves as a hub to integrate the biological outputs of the Raf-1 and Akt pathways.