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

本项目是正在进行的通过MAP激酶信号通路作用的癌基因转化机制的研究的继续。在过去的一年中，我们将我们的研究集中在DRM（被Mos下调）/Gremlin上，这是我们最初鉴定的基因，并且其表达在由多种癌基因转化的细胞中被下调。我们推测，这种表达的缺失可能对特定肿瘤的发生或进展很重要。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，体外合成的DRM可以在微粒体膜系统中被切割和糖基化，产生加工形式的蛋白质，其迁移率与培养中DRM产生细胞中产生的形式相同。预测的N-连接的糖基化位点的突变在体内和体外阻断糖基化，但不影响通过ER/高尔基体的加工或蛋白质运输。我们对表达内源性DRM或由转染的表达构建体编码的外源性DRM的细胞的分析显示，虽然大部分蛋白质与细胞相关，但一部分以可溶性形式释放到培养基中。细胞相关和可溶形式都能够干扰BMP-4信号传导，其诱导培养的C2 C12细胞的成骨分化。直接免疫沉淀和蛋白质交联研究也表明，DRM结合BMP在一个相对稳定的复合物，这表明DRM/Gremlin功能作为BMP拮抗剂的可能机制。突变的非糖基化DRM在两种测定中都是功能性的，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的DRM的作用和DRM改变胶质瘤和胶质母细胞瘤细胞系的生长特性的能力。 - mos、癌基因、逆转录病毒、肿瘤抑制因子、骨形态发生蛋白、MAPK、-人体组织、体液、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.