Niemann-Pick C1 disease:: Correlations between NPC1 mutations, levels of NPC1 protein, and phenotypes emphasize the functional significance of the putative sterol-sensing domain and of the cysteine-rich luminal loop
Niemann-Pick C1 disease:: Correlations between NPC1 mutations, levels of NPC1 protein, and phenotypes emphasize the functional significance of the putative sterol-sensing domain and of the cysteine-rich luminal loop
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DOI：
10.1086/320606
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发表时间：
2001-06-01
影响因子：
9.8
通讯作者：
Vanier, MT
中科院分区：
文献类型：
--
作者：
Millat, G;Marçais, C;Vanier, MT
为了获得NPC1蛋白功能域的更多信息，研究了30例无关的尼曼-匹克C1病患者皮肤成纤维细胞的突变谱和免疫反应蛋白水平。其中9例的特点是细胞胆固醇转运的轻微改变（“变异”生化表型）。突变广泛分布于几乎所有的NPC1结构域，在保守的富含半胱氨酸的NPC1管腔环中有一个簇（11/32）。14例患者的纯合子突变和表型定义的等位基因，加上另外10例患者的新突变，允许基因型/表型相关。过早终止密码子突变、固醇感应域（SSD）的三个错义突变和富含半胱氨酸的腔内环的A1054T突变都发生在婴儿神经系统发病和“典型”（严重）胆固醇转运改变的患者中。通过western blot检测，NPC1蛋白在研究的SSD错义突变（L724P和Q775P）中检测不到，在A1054T错义等位基因中基本不存在。因此，我们的研究结果增强了SSD的功能意义，并证明了NPC1蛋白缺失与最严重的神经系统形式之间的相关性。在研究的其余错义突变中，对应于其他疾病表现（包括两名患有非神经系统疾病的成年人），NPC1蛋白以正常大小的大量存在，与临床表型或“经典”/“变异”生化表型没有明确的相关性。富含半胱氨酸的管腔环的错义突变导致广泛的临床和生化表型。值得注意的是，所有五个突变等位基因（I943M, V950M, G986S， G992R和复发性P1007A）都与聚集在该环内的“变异”表型明确相关，为后一结构域的功能复杂性提供了新的见解。
To obtain more information of the functional domains of the NPC1 protein, the mutational spectrum and the level of immunoreactive protein were investigated in skin fibroblasts from 30 unrelated patients with Niemann-Pick C1 disease. Nine of them were characterized by mild alterations of cellular cholesterol transport (the "variant" biochemical phenotype). The mutations showed a wide distribution to nearly all NPC1 domains, with a cluster (11/32) in a conserved NPC1 cysteine-rich luminal loop. Homozygous mutations in 14 patients and a phenotypically defined allele, combined with a new mutation, in a further 10 patients allowed genotype/phenotype correlations. Premature-termination-codon mutations, the three missense mutations in the sterol-sensing domain (SSD), and A1054T in the cysteine-rich luminal loop all occurred in patients with infantile neurological onset and "classic" (severe) cholesterol-trafficking alterations. By western blot, NPC1 protein was undetectable in the SSD missense mutations studied (L724P and Q775P) and essentially was absent in the A1054T missense allele. Our results thus enhance the functional significance of the SSD and demonstrate a correlation between the absence of NPC1 protein and the most severe neurological form. In the remaining missense mutations studied, corresponding to other disease presentations (including two adults with nonneurological disease), NPC1 protein was present in significant amounts of normal size, without clear-cut correlation with either the clinical phenotype or the "classic"/"variant" biochemical phenotype. Missense mutations in the cysteine-rich luminal loop resulted in a wide array of clinical and biochemical phenotypes. Remarkably, all five mutant alleles (I943M, V950M, G986S, G992R, and the recurrent P1007A) definitively correlated with the "variant" phenotype clustered within this loop, providing new insight on the functional complexity of the latter domain.