Synergistic activation of stress-activated protein kinase 1/c-Jun N-terminal kinase (SAPK1/JNK) isoforms by mitogen-activated protein kinase kinase 4 (MKK4) and MKK7
Synergistic activation of stress-activated protein kinase 1/c-Jun N-terminal kinase (SAPK1/JNK) isoforms by mitogen-activated protein kinase kinase 4 (MKK4) and MKK7
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DOI：
10.1042/0264-6021:3520145
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发表时间：
2000-11-15
影响因子：
4.1
通讯作者：
Cohen, P
中科院分区：
文献类型：
--
作者：
Fleming, Y;Armstrong, CG;Cohen, P
应激激活蛋白激酶 1 (SAPK1)，也称为 c-Jun N 末端激酶 (JNK)，在体内响应促炎细胞因子或细胞应激而被激活。其完全激活需要 Thr-Pro-Tyr 基序中的苏氨酸和酪氨酸残基发生磷酸化，这可由蛋白激酶丝裂原激活蛋白激酶激酶 (MKK)4 和 MKK7 催化。在此，我们报告在测试的三种 SAPK1/JNK1 同工型（JNK1 α1、JNK2 α2 和 JNK3 α1）中，MKK4 对酪氨酸残基 (Tyr-185) 显示出显着偏好，而 MKK7 对苏氨酸残基 (Thr-183) 显示出显着偏好。因此，MKK4 和 MKK7 一起在体外协同增加每种 SAPK1/JNK 亚型的活性。 MKK7 beta 变体在激活所有三种 SAPK1/JNK 同工型方面的效率比 MKK7 alpha' 高数百倍，并且对 Thr-183 同样具有特异性。 MKK7 还在体外磷酸化 JNK2a2 Thr-404 和 Ser-407，Ser-407 在体外磷酸化比 Th-183 快得多，Thr-404/Ser-407 在未刺激的人 KB 细胞和 HEK-293 细胞中被磷酸化，并且磷酸化响应渗透压应激（0.5 M 山梨醇）而增加，然而，与 Thr-183 和Tyr-185、Thr-404 和 Ser-407 的磷酸化不会因激活 MKK7 和 SAPK1/JNK 的其他激动剂而增加，表明这些残基的磷酸化是由另一种蛋白激酶（例如 CK2）催化的，CK2 在体外也会磷酸化 Thr-404 和 Ser-407。 MKK3、MKK4 和 MKK6 均表现出对其已知底物 SAPK2a/p38、SAPK3/p38 gamma 和 SAPK4/p38 delta 中 Thr-Gly-Tyr 基序的酪氨酸残基磷酸化的强烈偏好。 MKK7 还以低速率磷酸化 SAPK2a/p38（但不是 SAPK3/p38 gamma 或 SAPK4/p38 delta），并且磷酸化仅发生在酪氨酸残基处，这表明 MKK7 本质上是一种“双特异性”蛋白激酶。
Stress-activated protein kinase 1 (SAPK1), also called c-Jun N-terminal kinase (JNK), becomes activated in vivo in response to pro-inflammatory cytokines or cellular stresses. Its full activation requires the phosphorylation of a threonine and a tyrosine residue in a Thr-Pro-Tyr motif, which can be catalysed by the protein kinases mitogen-activated protein kinase kinase (MKK)4 and MKK7. Here we report that MKK4 shows a striking preference for the tyrosine residue (Tyr-185), and MKK7 a striking preference for the threonine residue (Thr-183) in three SAPK1/JNK1 isoforms tested (JNK1 alpha1, JNK2 alpha2 and JNK3 alpha1). For this reason, MKK4 and MKK7 together produce a synergistic increase in the activity of each SAPK1/JNK isoform in vitro. The MKK7 beta variant, which is several hundred-fold more efficient in activating all three SAPK1/JNK isoforms than is MKK7 alpha', is equally specific for Thr-183. MKK7 also phosphorylates JNK2a2 at Thr-404 and Ser-407 in vitro, Ser-407 being phosphorylated much more rapidly than Th-183 in vitro, Thr-404/Ser-407 are phosphorylated in unstimulated human KB cells and HEK-293 cells, and phosphorylation is increased in response to an osmotic stress (0.5 M sorbitol), However, in contrast with Thr-183 and Tyr-185, the phosphorylation of Thr-404 and Ser-407 is not increased in response to other agonists that activate MKK7 and SAPK1/JNK, suggesting that phosphorylation of these residues is catalysed by another protein kinase, such as CK2, which also phosphorylates Thr-404 and Ser-407 in vitro. MKK3, MKK4 and MKK6 all show a strong preference for phosphorylation of the tyrosine residue of the Thr-Gly-Tyr motifs in their known substrates SAPK2a/p38, SAPK3/p38 gamma and SAPK4/p38 delta. MKK7 also phosphorylates SAPK2a/p38 at a low rate (but not SAPK3/p38 gamma or SAPK4/p38 delta), and phosphorylation occurs exclusively at the tyrosine residue, demonstrating that MKK7 is intrinsically a 'dual-specific' protein kinase.