Distinct cellular functions of MK2
Distinct cellular functions of MK2
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DOI：
10.1128/mcb.22.13.4827-4835.2002
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发表时间：
2002-07-01
影响因子：
5.3
通讯作者：
Gaestel, M
中科院分区：
文献类型：
--
作者：
Kotlyarov, A;Yannoni, Y;Gaestel, M
促分裂原活化蛋白激酶（MAPK）-活化蛋白激酶2（MK2）在应激时被p38 MAPK α和-β激活，其结合MK2的C末端的基本对接基序，随后磷酸化其调节位点。作为活化的结果，MK2从细胞核输出到细胞质，并将活性p38 MAPK共转运到该隔室。在这里，我们表明，p38 MAPK的量显着减少，在细胞和组织缺乏MK2，表明MK2对p38的稳定作用。使用小鼠基因敲除模型，我们以前已经表明，消除MK2导致显着减少肿瘤坏死因子（TNF）的生产响应脂多糖。为了进一步阐明MK2在p38 MAPK稳定和TNF生物合成中的作用，我们分析了两种MK2亚型和几种MK2突变体恢复巨噬细胞中p38 MAPK蛋白水平和TNF生物合成的能力。我们表明，MK2稳定p38 MAPK通过其C末端和MK2的催化活性并没有贡献这种稳定。重要的是，我们证明了稳定p38 MAPK不会恢复TNF的生物合成。TNF生物合成仅在MK2催化活性的情况下恢复。我们进一步表明，在MK2缺陷型巨噬细胞中，响应于细胞外刺激的丝状伪足的形成减少。此外，MK 2缺陷小鼠胚胎成纤维细胞（MEFs）和平滑肌细胞在纤连蛋白上的迁移显著减少。有趣的是，单独将催化MK2活性重新引入MEFs不足以逆转这些细胞的迁移表型。除了催化活性外，富含脯氨酸的N-末端区域对于拯救迁移表型是必要的。这些数据表明，MK2的催化活性是细胞因子产生和细胞迁移所必需的。然而，富含脯氨酸的MK 2 N末端提供了一个独特的作用，仅限于细胞迁移。
Mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2) is activated upon stress by p38 MAPKalpha and -beta, which bind to a basic docking motif in the C terminus of MK2 and which subsequently phosphorylate its regulatory sites. As a result of activation MK2 is exported from the nucleus to the cytoplasm and cotransports active p38 MAPK to this compartment. Here we show that the amount of p38 MAPK is significantly reduced in cells and tissues lacking MK2, indicating a stabilizing effect of MK2 for p38. Using a murine knockout model, we have previously shown that elimination of MK2 leads to a dramatic reduction of tumor necrosis factor (TNF) production in response to lipopolysaccharide. To further elucidate the role of MK2 in p38 MAPK stabilization and in TNF blosynthesis, we analyzed the ability of two MK2 isoforms and several MK2 mutants to restore both p38 MAPK protein levels and TNF biosynthesis in macrophages. We show that MK2 stabilizes p38 MAPK through its C terminus and that MK2 catalytic activity does not contribute to this stabilization. Importantly, we demonstrate that stabilizing p38 MAPK does not restore TNF biosynthesis. TNF biosynthesis is only restored with MK2 catalytic activity. We further show that, in MK2-deficient macrophages, formation of filopodia in response to extracellular stimuli is reduced. In addition, migration of MK2-deficient mouse embryonic fibroblasts (MEFs) and smooth muscle cells on fibronectin is dramatically reduced. Interestingly, reintroducing catalytic MK2 activity into MEFs alone is not sufficient to revert the migratory phenotype of these cells. In addition to catalytic activity, the proline-rich N-terminal region is necessary for rescuing the migratory phenotype. These data indicate that catalytic activity of MK2 is required for both cytokine production and cell migration. However, the proline-rich MK2 N terminus provides a distinct role restricted to cell migration.