Selective disactivation of neurofibromin GAP activity in neurofibromatosis type 1 (NF1)
Selective disactivation of neurofibromin GAP activity in neurofibromatosis type 1 (NF1)
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DOI：
10.1093/hmg/7.8.1261
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发表时间：
1998-08-01
影响因子：
3.5
通讯作者：
Nurnberg, P
中科院分区：
文献类型：
--
作者：
Klose, A;Ahmadian, MR;Nurnberg, P
1型神经纤维瘤病（NF 1）是一种常见的家族性肿瘤综合征，具有多种临床特征，如神经纤维瘤、黄斑斑（CLS）、虹膜Lisch结节、腋窝雀斑、视神经胶质瘤、特异性骨病变和恶性肿瘤风险增加。它是由影响NF 1基因的广谱突变引起的，大多数突变导致DNA上一个等位基因的丢失，mRNA或蛋白质水平，从而在基因产物神经纤维蛋白的任何功能的损失，几个不同的神经纤维蛋白功能的同时损失的想法已被假定来解释其损失的多效性效应。然而，我们已经在一个具有典型的多症状NF 1表型的家族（包括恶性神经鞘瘤）中鉴定出一种新的错义突变，该突变特异性地消除了神经纤维蛋白的Ras-GT β激活功能。在该家族中，Arg 1276突变为脯氨酸，基于复杂的生化研究以及对GTP酶激活蛋白（GAP）晶体结构的分析，p120 GAP结构域的Ras存在下，我们明确地确定了这个氨基酸作为神经纤维蛋白GAP相关结构域（GRD）的精氨酸指-RasGAP活性的最基本的催化元件，在这里，我们提出的数据表明，突变R1276 P，不像以前报道的GRD区域的错义突变，不损害蛋白质的二级和三级结构。它既不降低细胞神经纤维蛋白的水平，也不显著影响其与Ras的结合，但它确实完全使GAP活性失效。我们的研究结果提供了直接的证据表明，神经纤维蛋白GAP活性的失败是NF 1发病机制的关键因素，因此，旨在降低神经嵴源性细胞中Ras.GTP水平的治疗方法有望缓解大部分NF 1症状。
0Neurofibromatosis type 1 (NF1) is a common familial tumour syndrome with multiple clinical features such as neurofibromas, cafe-au-lait spots (CLS), iris Lisch nodules, axillary freckling, optic glioma, specific bone lesions and an increased risk of malignant tumours, It is caused by a wide spectrum of mutations affecting the NF1 gene, Most mutations result in the loss of one allele at the DNA, mRNA or protein level and thus in the loss of any function of the gene product neurofibromin, The idea of the simultaneous loss of several different neurofibromin functions has been postulated to explain the pleiotropic effects of its loss. However, we have identified a novel missense mutation in a family with a classical multi-symptomatic NF1 phenotype, including a malignant schwannoma, that specifically abolishes the Ras-GTPase-activating function of neurofibromin, In this family, Arg1276 had mutated into proline, Based on complex biochemical studies as well as the analysis of the crystal structure of the GTPase-activating protein (GAP) domain of p120GAP in the presence of Ras, we unequivocally identified this amino acid as the arginine finger of the neurofibromin GAP-related domain (GRD)-the most essential catalytic element for RasGAP activity, Here, we present data demonstrating that the mutation R1276P, unlike previously reported missense mutations of the GRD region, does not impair the secondary and tertiary protein structure. It neither reduces the level of cellular neurofibromin nor influences its binding to Ras substantially, but it does completely disable GAP activity. Our findings provide direct evidence that failure of neurofibromin GAP activity is the critical element of NF1 pathogenesis, Thus, therapeutic approaches aimed at the reduction of Ras.GTP levels in neural crest-derived cells can be expected to relieve most of the NF1 symptoms.