MECHANISMS OF INDUCTION AND SUPPRESSION OF VIRAL AND TUMOR-DERIVED ONCOGENE-DEPEN

这个项目是对癌基因转化机制的继续研究，这些癌基因通过MAP激酶信号通路发挥作用。在过去的一年里，我们的研究重点是DRM(Down-Regular by Mos)/Gremlin，这是我们最初发现的一个基因，它在多种癌基因转化的细胞中表达下调。我们推测，这种表达缺失可能在特定肿瘤的发生或发展中起重要作用。我们目前的工作集中在表征DRM的合成和性质，并分析其可能的功能。我们已经证明了体外合成的DRM可以在微粒体膜系统中被切割和糖基化，产生具有与在培养中产生的DRM产生的细胞相同的迁移率的蛋白质的加工形式。预测的N-连接糖基化位点的突变阻止了体内和体外的糖基化，但不影响加工或蛋白质通过内质网/高尔基体的运输。我们对表达内源性DRM或外源性DRM的细胞的分析表明，虽然大部分蛋白质是与细胞相关的，但一小部分以可溶性形式释放到介质中。细胞相关形式和可溶性形式均可干扰诱导C2C12细胞成骨分化的BMP-4信号转导。直接免疫沉淀和蛋白质交联研究也表明DRM与BMP以相对稳定的复合体结合，提示DRM/Gremlin可能作为BMP拮抗剂发挥作用。突变的非糖基化DRM在两种检测中都具有功能，表明BMP结合不需要糖基化。正在进行的工作集中在可溶性和细胞相关DRM的作用以及DRM改变胶质瘤和胶质母细胞瘤细胞系生长特性的能力上。-MOS，癌基因，逆转录病毒，肿瘤抑制因子，骨形成蛋白，MAPK，-人体组织，液体，细胞等

This project is a continuation of ongoing studies of the mechanism of transformation by oncogenes that act through the MAP kinase signaling pathway. During the past year we have focused our studies on DRM (Down- Regulated by Mos)/Gremlin, a gene which we initially identified and whose expression was down-regulated in cell transformed by a variety of oncogenes. We have theorized that this loss of expression may be important for the initiation or progression of specific tumors. Our current efforts have focused on characterizing the synthesis and properties of DRM and analyzing its possible function. We have demonstrated that in-vitro synthesized DRM can be cleaved and glycosylated in a microsomal membrane system, generating processed forms of the protein with mobilities identical to the forms generated in DRM producing cells in culture. Mutation of the predicted N-linked glycosylation site blocked glycosylation both in vivo and in vitro but did not affect processing or protein trafficking through the ER/Golgi. Our analysis of cells expressing either endogenous DRM, or exogenous DRM encoded by transfected expression constructs, revealed that while the bulk of the protein was cell associated, a fraction was released into the media in a soluble form. Both cell associated and soluble forms were capable of interfering with BMP-4 signaling which induced osteogenic differentiation of C2C12 cells in culture. Direct immunoprecipitation and protein crosslinking studies also demonstrated that DRM bound BMP in a relatively stable complex, suggesting a possible mechanism of DRM/Gremlin function as a BMP antagonist. Mutant non-glycosylated DRM was functional in both assays, indicating that glycosylation was not required for BMP binding. Ongoing work is focusing on the role of soluble and cell associated DRM and the ability of DRM to alter the growth properties of gliomas and glioblastoma cell lines. - mos, Oncogene, retrovirus, Tumor Suppressor, Bone Morphogenetic Proteins, MAPK, - Human Tissues, Fluids, Cells, etc.