Role for Tyrosine Phosphorylation of A-kinase Anchoring Protein 8 (AKAP8) in Its Dissociation from Chromatin and the Nuclear Matrix
Role for Tyrosine Phosphorylation of A-kinase Anchoring Protein 8 (AKAP8) in Its Dissociation from Chromatin and the Nuclear Matrix
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DOI：
10.1074/jbc.m115.643882
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发表时间：
2015-04-24
影响因子：
4.8
通讯作者：
Yamaguchi, Naoto
中科院分区：
文献类型：
--
作者：
Kubota, Sho;Morii, Mariko;Yamaguchi, Naoto
蛋白质酪氨酸磷酸化在质膜上调节多种细胞过程。最近，我们发现核酪氨酸激酶引起整体核结构的改变，我们称之为染色质结构改变。然而，其机制尚不完全清楚。在本研究中，我们鉴定了蛋白激酶A锚定蛋白8(AKAP8/AKAP95)，它与染色质和核基质有关，是一种核酪氨酸磷酸化蛋白。AKAP8的酪氨酸磷酸化被几种酪氨酸激酶诱导，如Src、Fyn和c-Abl，但不能诱导Syk。核靶向的Lyn和c-Src以一种依赖于激酶活性的方式强烈地将AKAP8从染色质和核基质中分离出来。通过将AKAP8上的多个酪氨酸残基替换为苯丙氨酸，降低了AKAP8的酪氨酸磷酸化水平。重要的是，AKAP8的苯丙氨酸突变抑制了它与核结构的解离，这表明AKAP8与核结构的结合/解离受其酪氨酸磷酸化的调节。此外，AKAP8的苯丙氨酸突变抑制了核酪氨酸激酶诱导的染色质结构变化。相反，AKAP8基因敲除会增加染色质结构变化的水平。有趣的是，过氧化氢刺激导致染色质结构改变，并伴随着AKAP8从核结构中解离。这些结果表明，AKAP8通过核酪氨酸磷酸化参与了染色质结构变化的调节。
Protein-tyrosine phosphorylation regulates a wide variety of cellular processes at the plasma membrane. Recently, we showed that nuclear tyrosine kinases induce global nuclear structure changes, which we called chromatin structural changes. However, the mechanisms are not fully understood. In this study we identify protein kinase A anchoring protein 8 (AKAP8/AKAP95), which associates with chromatin and the nuclear matrix, as a nuclear tyrosine-phosphorylated protein. Tyrosine phosphorylation of AKAP8 is induced by several tyrosine kinases, such as Src, Fyn, and c-Abl but not Syk. Nucleus-targeted Lyn and c-Src strongly dissociate AKAP8 from chromatin and the nuclear matrix in a kinase activity-dependent manner. The levels of tyrosine phosphorylation of AKAP8 are decreased by substitution of multiple tyrosine residues on AKAP8 into phenylalanine. Importantly, the phenylalanine mutations of AKAP8 inhibit its dissociation from nuclear structures, suggesting that the association/dissociation of AKAP8 with/from nuclear structures is regulated by its tyrosine phosphorylation. Furthermore, the phenylalanine mutations of AKAP8 suppress the levels of nuclear tyrosine kinase-induced chromatin structural changes. In contrast, AKAP8 knockdown increases the levels of chromatin structural changes. Intriguingly, stimulation with hydrogen peroxide induces chromatin structural changes accompanied by the dissociation of AKAP8 from nuclear structures. These results suggest that AKAP8 is involved in the regulation of chromatin structural changes through nuclear tyrosine phosphorylation.