Phosphorylation of human keratin 18 serine 33 regulates binding to 14-3-3 proteins
Phosphorylation of human keratin 18 serine 33 regulates binding to 14-3-3 proteins
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DOI：
10.1093/emboj/17.7.1892
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发表时间：
1998-04-01
期刊：
影响因子：
11.4
通讯作者：
Omary, MB
中科院分区：
文献类型：
--
作者：
Ku, NO;Liao, J;Omary, MB
14-3-3蛋白家族的成员在体内以细胞周期和磷酸化依赖的方式与人中间丝蛋白K18(K18)结合。我们发现K18Ser33是一个间期磷酸化位点，在培养细胞和再生肝有丝分裂过程中增加其磷酸化，并在体外作为cdc2激酶的磷酸化位点。野生型与K18Ser33--&Gt；Ala/Asp转基因细胞的比较表明，K18Ser33的磷酸化对于K18与14-3-3蛋白的结合是必不可少的，并在角蛋白的组织和分布中发挥作用。K18的另一个主要磷酸化位点(Ser52)或K18糖基化位点的突变对K18与14-3-3蛋白的结合没有影响。K18磷酸-Ser33基序不同于已描述的几个14-3-3结合的磷酸化基序。针对K18磷酸化丝氨酸33或磷酸化丝氨酸52的抗体表明，尽管丝氨酸52和丝氨酸33磷酸化的K18分子表现出部分共存，但这些磷酸化事件主要存在于不同的K18分子上。我们的结果表明，一个独特的K18磷酸化位点是K18与14-3-3蛋白结合的必要条件，但不是充分条件。这种结合可能涉及一个或多个与K18Ser33磷酸化偶联的有丝分裂事件，并在角蛋白的亚细胞分布中发挥作用。不同K18分子上的生理性Ser52或Ser33磷酸化提示这些修饰的功能区隔。
Members of the 14-3-3 protein family bind the human intermediate filament protein keratin 18 (K18) in vivo, in a cell-cycle-and phosphorylation-dependent manner. We identified K18 Ser33 as an interphase phosphorylation site, which increases its phosphorylation during mitosis in cultured cells and regenerating liver, and as an in vitro cdc2 kinase phosphorylation site. Comparison of wild-type versus K18 Ser33-->Ala/Asp transfected cells showed that K18 Ser33 phosphorylation is essential for the association of K18 with 14-3-3 proteins, and plays a role in keratin organization and distribution. Mutation of another K18 major phosphorylation site (Ser52) or K18 glycosylation sites had no effect on the binding of K18 to 14-3-3 proteins. The K18 phospho-Ser33 motif is different from several 14-3-3-binding phosphomotifs already described. Antibodies that are specific to K18 phospho-Ser33 or phospho-Ser52 show that although Ser52 and Ser33 phosphorylated K18 molecules manifest partial colocalization, these phosphorylation events reside predominantly on distinct K18 molecules. Our results demonstrate a unique K18 phosphorylation site that is necessary but not sufficient for K18 binding to 14-3-3 proteins. This binding is likely to involve one or more mitotic events coupled to K18 Ser33 phosphorylation, and plays a role in keratin subcellular distribution. Physiological Ser52 or Ser33 phosphorylation on distinct K18 molecules suggests functional compartmentalization of these modifications.