Serum-dependent phosphorylation of human MAP4 at Ser696 in cultured mammalian cells
Serum-dependent phosphorylation of human MAP4 at Ser696 in cultured mammalian cells
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DOI：
10.1247/csf.24.321
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发表时间：
1999-10-01
影响因子：
1.5
通讯作者：
Hisanaga, S
中科院分区：
文献类型：
--
作者：
Srsen, V;Kitazawa, H;Hisanaga, S
在先前的论文中{Ookata et al.，（1997）Biochemistry，36：249-259}，我们在人MAP 4的富含脯氨酸的区域中鉴定了两个有丝分裂cdc 2激酶磷酸化位点（Ser 696和Ser 787）。其中一个（Ser 696）在间期也被磷酸化。负责Ser 696的间期磷酸化的蛋白激酶必然不同于cdc 2/细胞周期蛋白B激酶。为了深入了解Ser 696磷酸化的生理作用，我们寻找Ser 696激酶和Ser 696去磷酸化的细胞条件。因为Ser 696符合MAP激酶磷酸化共有基序（PXSP），所以MAP激酶被测试为可能的激酶磷酸化Ser 696。事实上，MAP激酶在体外确实磷酸化了MTB 3中的Ser 696，MTB 3是人类MAP 4的羧基末端的一半。HeLa细胞提取物中Ser 696的磷酸化被MAP激酶抑制剂DBTM-0004抑制。与Ser 696是MAP激酶位点的概念一致的还有以下事实：血清饥饿诱导HeLa细胞、TIG-3和MRC-5-30人成纤维细胞中Ser 696的去磷酸化，而血清再加入恢复了Ser 696的磷酸化，尽管经过了令人惊讶的长时间间隔。因此，MAP 4的Ser 696的磷酸化，最有可能由MAP激酶进行，可能在增殖与静止细胞中的MAP 4活性的调节中起作用。
In the previous paper {Ookata et al., (1997) Biochemistry, 36: 249-259}, we identified two mitotic cdc2 kinase phosphorylation sites (Ser696 and Ser787) in the proline-rich region of human MAP4. One (Ser696) of them was also phosphorylated during interphase. A protein kinase responsible for interphase phosphorylation of Ser696 could necessarily be distinct from cdc2/cyclin B kinase, To get insights into a physiological role for Ser696 phosphorylation, we searched for a Ser696 kinase and for cellular conditions under which Ser696 is dephosphorylated. Because Ser696 conforms to the MAP kinase phosphorylation consensus motif (PXSP), MAP kinase was tested as a possible kinase phosphorylating Ser696. MAP kinase, in fact, did phosphorylate Ser696 in MTB3, the carboxy-terminal half of human MAP4 in vitro. Phosphorylation of Ser696 in HeLa cell extract was suppressed by a MAP kinase inhibitor, DBTM-0004. Also consistent with the notion that Ser696 is a MAP kinase site were the fact that serum-starvation induced dephosphorylation of Ser696 in HeLa cells, TIG-3 and MRC-5-30 human fibroblasts, while readdition of serum recovered Ser696 phosphorylation, albeit after a surprisingly long interval. Thus, phosphorylation of Ser696 of MAP4, most likely carried out by MAP kinase, may play a role in modulation of MAP4 activity in proliferating versus quiescent cells.