Loss of Membrane Targeting of Vangl Proteins Causes Neural Tube Defects
Loss of Membrane Targeting of Vangl Proteins Causes Neural Tube Defects
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DOI：
10.1021/bi101286d
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发表时间：
2011-02-08
期刊：
影响因子：
2.9
通讯作者：
Gros, Philippe
中科院分区：
文献类型：
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作者：
Iliescu, Alexandra;Gravel, Michel;Gros, Philippe
在小鼠中，环尾突变（Lp）会导致非常严重的神经管缺陷，这是由 Vangl2 基因突变引起的。在哺乳动物中，Vangl1 和 Vangl2 编码整合膜蛋白，这些蛋白组装成不对称分布的膜复合物，在上皮细胞中建立平面细胞极性，并在胚胎发生过程中调节会聚延伸运动。迄今为止，VANGL 是唯一一个突变导致人类神经管缺陷的基因。 Vangl2 已描述了三个独立产生的 Lp 等位基因：D255E、S464N 和 R259L。在这里，我们报告了天然存在的 Lp (S464N) 和新的 ENU 诱导突变 Lp(m2Jus)(R259L) 的共同机制。我们发现，在极化 MDCK 肾细胞中稳定表达的 S464N 和 R259L 变体无法到达质膜，而质膜是其发挥生物学功能的部位。突变体保留在细胞内的内质网中，与内质网伴侣钙网蛋白共定位。此外，突变体还表现出半衰期显着缩短，约为 3 小时，而野生型蛋白的半衰期约为 22 小时，并且以蛋白酶体依赖性和 MG132 敏感的方式快速降解。将三个已知等位基因 Lp 变体与野生型蛋白单独共表达并不影响 WT 在质膜上的定位，这表明体内 Lp 性状的共显性性质是由于基因剂量依赖性途径部分功能丧失引起的单倍体不足，而不是显性失活表型。我们的研究为研究最近发现的散发性或家族性神经管缺陷病例中 hVANGL1 和 hVANGL2 突变的研究提供了一个生化框架。
In the mouse, the loop-tail mutation (Lp) causes a very severe neural tube defect, which is caused by mutations in the Vangl2 gene. In mammals, Vangl1 and Vangl2 code for integral membrane proteins that assemble into asymmetrically distributed membrane complexes that establish planar cell polarity in epithelial cells and that regulate convergent extension movements during embryogenesis. To date, VANGL are the only genes in which mutations cause neural tube defects in humans. Three independently arising Lp alleles have been described for Vangl2: D255E, S464N, and R259L. Here we report a common mechanism for both the naturally occurring Lp (S464N) and a novel ENU-induced mutation Lp(m2Jus)(R259L). We show that the S464N and R259L variants stably expressed in polarized MDCK kidney cells fail to reach the plasma membrane, their site for biological function. The mutant variants are retained intracellularly in the endoplasmic reticulum, colocalizing with ER chaperone calreticulin. Furthermore, the mutants also show a dramatically reduced half-life of similar to 3 h, compared to similar to 22 h for the wild-type protein, and are rapidly degraded in a proteasome-dependent and MG132-sensitive fashion. Coexpressing individually the three known allelic Lp variants with the wild-type protein does not influence the localization of the WT at the plasma membrane, suggesting that the codominant nature of the Lp trait in vivo is due to haploid insufficiency caused by a partial loss of function in a gene dosage-dependent pathway, as opposed to a dominant negative phenotype. Our study provides a biochemical framework for the study of recently identified mutations in hVANGL1 and hVANGL2 in sporadic or familial cases of neural tube defects.