Structural Biology of Cell Surface Mucin Domains

描述（由申请人提供）： 粘蛋白糖蛋白结构域是在包括免疫系统的细胞类型的各种细胞上普遍存在的细胞表面景观的重要组分。这些的特征在于其序列中高水平的O-糖基化丝氨酸和苏氨酸。具有这种粘蛋白结构域的两种蛋白质CD 43和CD 45占T细胞表面的约30%。这些结构域在细胞-细胞相互作用和识别中是重要的，并且与这些事件相关的分子定位对由其胞内结构域介导的信号转导事件具有影响。糖蛋白的碳水化合物和多肽组分都有助于分子识别，其中O-糖基化具有深刻的构象效应，诱导蛋白质骨架的延伸排列。这些糖蛋白上的碳水化合物表位的重要性通过其随细胞状态、发育阶段和疾病的特定变化而得到证实，为细胞信号传导的多样性提供了额外的维度，并为细胞特异性治疗干预提供了靶标。CD 43的延伸结构使其成为外部环境遇到的第一个细胞成分之一。由于分子识别对这些糖蛋白的作用至关重要，因此拟议的研究将研究它们的结构，以了解功能和相互作用。这些分子在很大程度上抵制详细的结构分析，因为难以从天然来源中分离出合适的均质材料。最初，我们的研究表明，化学合成和核磁共振光谱技术可以结合起来，以获得高分辨率的描述粘蛋白基序从CD 43。我们的目标是扩展这一点，第一，以确定其他代表性的图案的结构，并进一步阐明控制分子组织的原则，第二，使用这一特性较大的粘蛋白片段，第三，将其与其他分子，如抗体和半乳糖凝集素的识别。CD 43和CD 45与半乳糖凝集素-1的相互作用导致它们分离成单独的斑块，并最终导致T细胞程序性细胞死亡。我们的研究将检查这种相互作用，提供深入了解这一过程和可能的控制自身免疫性疾病。在肿瘤细胞上，这些糖蛋白的特征在于它们的异常糖基化，并且对结构的理解可以帮助进一步开发糖肽抗肿瘤疫苗。

DESCRIPTION (provided by applicant): Mucin glycoprotein domains are important components of the cell surface landscape prevalent on various cell types including those of the immune system. These are characterized by a high level of O-glycosyalted serine and threonine in their sequences. Two proteins with such mucin domains, CD43 and CD45, comprise about 30% of the surface of T-cells. Such domains are significant in cell-cell interactions and recognition, and molecular localization related to these events have consequences for the signal transduction events mediated by their intracellular domains. Both carbohydrate and polypeptide components of the glycoproteins contribute to molecular recognition, with O-glycosylation having a profound conformational effect, inducing an extended arrangement of the protein backbone. The significance of the carbohydrate epitopes on these glycoproteins is born out by their specific variation with the state of the cell, stage of development and disease, offering an additional dimension to the diversity for cellular signaling and a target for cell specific therapeutic intervention. The extended structure of CD43 makes it one of the first cellular components encountered by the outside environment. Since molecular recognition is central to the roles of these giycoproteins, the proposed research will investigate their structure, required to understand function and interactions. These molecules have resisted detailed structural analysis in large part because of difficulties in isolating suitable homogeneous material from natural sources. Initially, our studies have demonstrated that chemical synthesis and nuclear magnetic resonance spectroscopy techniques can be joined to obtain a high resolution description of a mucin motif from CD43. Our aims are to extend this, first, to determine structures of other representative motifs and further elucidate the principles controlling molecular organization, second, to use this in characterizing larger segments of mucins, and third to relate this to their recognition by other molecules such as antibodies and galectin. Interactions of CD43 and CD45 with galectin-1 causes their segregation into separate patches and ultimately T-cell programmed cell death. Our studies will examine this interaction, providing insight into this process and into possible control of autoimmune disease. On tumor cells, these glycoproteins are characterized by their aberrant glycosylation, and a structural understanding could aid in further development of glycopeptide anti-tumor vaccines.