Functional regulation of FEZ1 by the U-box-type ubiquitin ligase E4B contributes to neuritogenesis
Functional regulation of FEZ1 by the U-box-type ubiquitin ligase E4B contributes to neuritogenesis
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DOI：
10.1074/jbc.m402916200
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发表时间：
2004-12-17
影响因子：
4.8
通讯作者：
Nakayama, KI
中科院分区：
文献类型：
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作者：
Okumura, F;Hatakeyama, S;Nakayama, KI
E4b(也称为UFD2a)是酿酒酵母Ufd2的哺乳动物同源物，最初被描述为泛素链组装因子(E4)。E4B是一种U盒型泛素蛋白异肽连接酶(E3)，可能具有E3或E4的功能。通过酵母双杂交筛选，我们现在已经鉴定FEZ1(束状和延伸蛋白Zeta 1)是一种与E4B相互作用的蛋白质。当FEZ1被蛋白激酶ZETA(PKZETA)磷酸化时，FEZ1与神经发生有关。在哺乳动物细胞中，E4B和FEZ1之间的相互作用可以通过共表达组成活性的PKzzeta来增强。E4B介导了FEZ1的多泛素化，但不影响其细胞内的稳定性，提示FEZ1的这种修饰不是其蛋白降解的信号。E4B使FEZ1多泛素化需要泛素的Lys(27)。E4B显性-负性突变体在大鼠嗜铬细胞瘤PC12细胞中的表达可抑制神经生长因子或FEZ1与其固有活性的PKcheeta共表达所诱导的突起伸展。这些发现表明，E4B作为FEZ1的泛素连接酶，从而调节其功能，但不调节其降解。
E4B ( also known as UFD2a) is a mammalian homolog of Saccharomyces cerevisiae Ufd2, which was originally described as a ubiquitin chain assembly factor (E4). E4B is a U-box-type ubiquitin-protein isopeptide ligase (E3) and likely functions as either an E3 or an E4. With a yeast two-hybrid screen, we have now identified FEZ1 (fasciculation and elongation protein zeta 1) as a protein that interacts with E4B. FEZ1 is implicated in neuritogenesis when phosphorylated by protein kinase Czeta (PKCzeta). Interaction between E4B and FEZ1 in mammalian cells was enhanced by coexpression of constitutively active PKCzeta. E4B mediated the polyubiquitylation of FEZ1 but did not affect its intracellular stability, suggesting that such modification of FEZ1 is not a signal for its proteolysis. Polyubiquitylation of FEZ1 by E4B required Lys(27) of ubiquitin. Expression of a dominant-negative mutant of E4B in rat pheochromocytoma PC12 cells resulted in inhibition of neurite extension induced either by nerve growth factor or by coexpression of FEZ1 and constitutively active PKCzeta. These findings indicate that E4B serves as a ubiquitin ligase for FEZ1 and thereby regulates its function but not its degradation.