Absence of post-translational aspartyl β-hydroxylation of epidermal growth factor domains in mice leads to developmental defects and an increased incidence of intestinal neoplasia
Absence of post-translational aspartyl β-hydroxylation of epidermal growth factor domains in mice leads to developmental defects and an increased incidence of intestinal neoplasia
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DOI：
10.1074/jbc.m110389200
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发表时间：
2002-04-12
影响因子：
4.8
通讯作者：
Friedman, PA
中科院分区：
文献类型：
--
作者：
Dinchuk, JE;Focht, RJ;Friedman, PA
BAH基因组位点编码三种不同的蛋白质：连接蛋白、欺骗蛋白和BAH。所有三种蛋白质共享共同的外显子，但基于替代末端外显子的使用而显著不同。BAH和humbug的生物学作用及其与连接蛋白的功能关系尚不清楚。为了评估BAH在体内的作用，BAH的催化结构域被特异性靶向，使得连接蛋白和欺骗蛋白的编码区保持不受干扰。BAH敲除小鼠在几种组织中缺乏可测量的BAH蛋白，在肝脏制备物中缺乏乙酰β-羟化酶活性，并且凝血因子X的表皮生长因子（EGF）结构域没有羟基化。除了雌性生育力降低外，BAH基因敲除小鼠还表现出几种发育缺陷，包括并指畸形、面部畸形和硬腭形成的轻度缺陷。BAH缺失小鼠中存在的发育缺陷与Notch配体Serrate-2的敲除和亚型中观察到的缺陷相似。在这项工作中，EGF结构域中Asp残基的β-羟基化被证明是Notch配体的可溶形式，人Jagged-1。这些结果沿着最近的报道，即Notch基因家族成员中EGF结构域的另一种翻译后修饰（通过Fringe的糖基化）改变了Notch途径信号传导，这为如下建议提供了证据，即乙酰基β-羟基化可能代表可以调节Notch途径信号传导的EGF结构域的另一种翻译后修饰。先前的工作已经证明了在某些肿瘤组织中BAH水平的增加，并且已经提出了BAH在肿瘤发生中的作用。通过将BAH KO小鼠与肠肿瘤模型APCmin小鼠杂交直接测试羟化酶在肿瘤形成中的作用。令人惊讶的是，与BAH野生型/APCmin对照相比，BAH null/APCmin小鼠显示出肠息肉大小和数量的统计学显著增加。这些结果表明，与预期相反，BAH催化活性的丧失可能促进肿瘤形成。
The BAH genomic locus encodes three distinct proteins: junctin, humbug, and BAH. All three proteins share common exons, but differ significantly based upon the use of alternative terminal exons. The biological roles of BAH and humbug and their functional relationship to junctin remain unclear. To evaluate the role of BAH in vivo, the catalytic domain of BAH was specifically targeted such that the coding regions of junctin and humbug remained undisturbed. BAH null mice lack measurable BAH protein in several tissues, lack aspartyl beta-hydroxylase activity in liver preparations, and exhibit no hydroxylation of the epidermal growth factor (EGF) domain of clotting Factor X. In addition to reduced fertility in females, BAH null mice display several developmental defects including syndactyly, facial dysmorphology, and a mild defect in hard palate formation. The developmental defects present in BAH null mice are similar to defects observed in knock-outs and hypomorphs of the Notch ligand Serrate-2. In this work, beta-hydroxylation of Asp residues in EGF domains is demonstrated for a soluble form of a Notch ligand, human Jagged-1. These results along with recent reports that another post-translational modification of EGF domains in Notch gene family members (glycosylation by Fringe) alters Notch pathway signaling, lends credence to the suggestion that aspartyl beta-hydroxylation may represent another post-translational modification of EGF domains that can modulate Notch pathway signaling. Previous work has demonstrated increased levels of BAH in certain tumor tissues and a role for BAH in tumorigenesis has been proposed. The role of hydroxylase in tumor formation was tested directly by crossing BAH KO mice with an intestinal tumor model, APCmin mice. Surprisingly, BAH null/APCmin mice show a statistically significant increase in both intestinal polyp size and number when compared with BAH wild-type/APCmin controls. These results suggest that, in contrast to expectations, loss of BAH catalytic activity may promote tumor formation.