Mechanisms regulating glycan expression and function

描述(申请人提供)：所有真核细胞的表面都富含复杂的糖结合物。细胞表面的多聚糖与它们所连接的蛋白质和脂类骨架一起形成了细胞与细胞相互作用的界面。与它们的亚细胞位置和巨大的结构多样性相一致，特定的多糖作为细胞表面标签，允许细胞彼此适当地相互作用，并与当地环境相互作用。因此，控制多糖表达的机制也控制着发育、免疫和病理细胞行为。利用遗传和分子技术，我们发现果蝇Toll样受体(TLR)，称为Tollo/Toll-8，是导致组织特异性多糖表达的机制的关键组成部分。Tollo的活性诱导了一组N-连接的寡糖的神经特异性表达，称为HRP表位。Tollo在神经元上不表达，但在接触分化神经元的外胚层细胞上发现。TLR的这一新功能为理解细胞间的相互作用如何影响组织特异性糖基化提供了手段。Tollo信号传播的分子途径将通过产生影响HRP表位表达的新突变来确定和表征。除了我们的突变筛选外，我们还将确定以前发现的基因是否也活跃在调节多糖表达的过程中，这些基因在其他情况下是TLR信号通路的组成部分。为了放置新的基因并确定Tollo功能的细胞机制，我们将研究改变形式的Tollo诱导神经特异性糖基化的能力。最后，将通过测定胚胎中HRP表位的多样性和表征Tollo功能丧失引起的糖链变化来评估Tollo诱导的多糖表达的特异性。特异性糖基化对正常组织功能的重要性表明，控制多糖表达的机制最终应该为治疗包括中枢神经系统损伤、炎症/免疫紊乱和肿瘤细胞转移在内的广泛的人类病理提供新的靶点。

DESCRIPTION (provided by applicant): The surfaces of all eukaryotic cells are richly endowed with complex glycoconjugates. Cell surface glycans, together with the protein and lipid backbones to which they are linked, form the interfaces at which cell-cell interactions occur. Consistent with their subcellular location and immense structural diversity, specific glycans function as cell surface tags that allow cells to appropriately interact with each other and with their local environment. Therefore, mechanisms that control glycan expression also control developmental, immunological, and pathological cellular behaviors. Using genetic and molecular techniques, we discovered that a Drosophila Toll-like receptor (TLR), called Tollo/Toll-8, is a key component of a mechanism that leads to tissue-specific glycan expression. Tollo activity induces the neural-specific expression of a set of N-linked oligosaccharides known as the HRP-epitope. Tollo is not expressed on neurons but is found on ectodermal cells that contact differentiating neurons. This new function for a TLR provides the means to understand how cell-cell interactions influence tissue-specific glycosylation. The molecular pathway through which the Tollo signal is propagated will be identified and characterized by generating new mutations that affect expression of the HRP-epitope. In addition to our mutagenesis screen, we will determine whether previously identified genes, that are components of TLR signaling pathways in other contexts, are also active in regulating glycan expression. To place new genes in context and to determine the cellular mechanism of Tollo function, the ability of altered forms of Tollo to induce neural-specific glycosylation will be investigated. Finally, the specificity of Tollo induced glycan expression will be assessed by determining the diversity of HRP-epitopes in the embryo and by characterizing the full extent of glycan changes caused by loss of Tollo function. The importance of specific glycosylation for normal tissue function indicates that mechanisms controlling glycan expression should ultimately provide new targets for therapeutic intervention in a broad range of human pathologies, including CNS injury, inflammatory/immune disorders, and tumor cell metastasis.