Study on cellular signal transduction of Neurofibromatosis Type 1 and Type 2 tumor suppressor gene products

神经纤维瘤病1型（NF 1）和2型（NF 2）是一种常染色体显性遗传疾病，与双侧前庭神经鞘瘤、脑膜瘤和胶质瘤等颅内肿瘤的发生密切相关。NF 1和NF 2基因最近在不同的基因座上被鉴定，并且发现它们编码的蛋白质（对于NF 1被称为神经纤维蛋白，对于NF 2被称为merlin）尽管它们的病理相似性，但没有同源性。为了阐明NF 1和NF 2蛋白的生物学功能，我们通过细胞蛋白质组学和生物学策略分析了它们的信号转导。1）NF 1：神经纤维蛋白具有充当GAP的结构域，并且被认为是重要的Ras调节剂。我们确定了35个新的细胞神经纤维蛋白相关蛋白。14-3-3被认为是NF 1调节剂最有趣的核心候选者之一。14-3-3主要作用于神经纤维蛋白的C末端结构域（CTD），与cAMP依赖性蛋白激酶（PKA）相互作用。 ...更多信息 在CTD-Ser（2576，2578，2580，2813）和Thr（2556）上聚集的ent磷酸化是相互作用所必需的。有趣的是，增加的磷酸化和14-3-3的缔合负调节神经纤维蛋白差距活性。这些发现表明，PKA磷酸化后的14-3-3蛋白和其他蛋白质簇的相互作用可能会调节细胞神经纤维蛋白的生化和生物学功能。（2）NF 2：经MAS分析鉴定，merlin的细胞结合蛋白为多聚ADP核糖聚合酶、DNA-PK亚基Ku抗原85和70。Merlin蛋白的N端（19-339）区域是它们相互作用的关键。merlin和PARP的亚细胞共定位主要在它们的核区域，并具有merlin的核输出信号（内斯）依赖性。而PARP基因缺陷的MEF即使经LMB或博莱霉素处理后，其细胞核内也不能积累merlin。这些结果表明，merlin是一种细胞质-核穿梭蛋白，其转运途径依赖于NES，与PARP有关。merlin的肿瘤抑制功能可能通过细胞merlin结合蛋白如PARP和DNA-PK的相互作用与细胞DNA修复和相关信号相关。少

The neurofibromatosis type 1 (NF1) and type 2 (NF2) are autosomal dominantly inherited disorders, and strongly associated with development of intracranial tumors including bilateral vestibular schwannomas, meningiomas and gliomas. NF1 and NF2 genes were recently identified on the different locus, and the proteins they encode (termed as neurofibromin for NF1 and merlin for NF2) were found to be no homologies despite of their pathological similarity. To elucidate the biological function of NF1 and NF2 proteins, we analyzed their signal transductions by cellular proteomic and biological strategies. 1)NF1 : Neurofibromin has a domain acting as a GAP and thought to be an important Ras regulator. We identified 35 novel cellular neurofibromin-associating proteins. 14-3-3 was identified as one of the most interesting core candidates of NF1 regulators. The interaction of 14-3-3 is mainly directed to the C-terminal domain (CTD) of neurofibromin, and the cAMP-dependent protein kinase (PKA)-depend … More ent phosphorylation clustered on CTD-Ser (2576, 2578, 2580, 2813) and Thr (2556) is required for the interaction. Interestingly, the increased phosphorylation and association of 14-3-3 negatively regulate the GAP activity of neurofibromin. These findings indicate that PKA phosphorylation followed by 14-3-3 protein and other protein cluster interactions may modulate the biochemical and biological functions of cellular neurofibromin. 2)NF2 ; Cellular binding proteins of merlin were identified as poly ADP-ribose polymerase, DNA-PK subunits Ku-antigen 85 and 70 by MAS spec analysis. The N-terminal (19-339) region of merlin is essential for their interaction. Subcellular co-localizations of merlin and PARP were observed mainly in their nuclear region with a nuclear export signal (NES) dependent manner of merlin. This nuclear accumulation increased with cellular DNA damages, whereas PARP gene deficient MEF could not accumulate merlin in their nuclear region, even after the treatments of LMB or bleomycin, These results suggest that merlin is a cytoplasmic-nuclear shuttling protein directed by its NES-dependent transport pathway being associated with PARP. The tumor suppressive function of merlin may be linked to cellular DNA-repair and related signals via the interaction of cellular merlin binding proteins such as PARP and DNA-PKs. Less