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细胞表面景观的重要组成部分，普遍存在于包括免疫系统在内的各种细胞类型中。它们的特征是它们的序列中含有高水平的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CD43和CD45约占T细胞表面的30%。这些结构域在细胞间的相互作用和识别中具有重要意义，与这些事件相关的分子定位对其胞内结构域介导的信号转导事件产生影响。糖蛋白的碳水化合物和多肽成分都有助于分子识别，O-糖基化具有深刻的构象效应，导致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是由于它们随着细胞状态、发育阶段和疾病的特定变化而产生的，为细胞信号的多样性提供了额外的维度，并成为细胞特异性治疗干预的靶点。CD43的扩展结构使其成为外界环境最先遇到的细胞组件之一。由于分子识别是这些糖蛋白作用的核心，拟议的研究将调查它们的结构，这是了解功能和相互作用所必需的。这些分子在很大程度上抵制详细的结构分析，因为很难从自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技术可以结合起来，从CD43获得粘蛋白基序的高分辨率描述。我们的目标是扩展这一点，第一，确定其他代表性基序的结构，并进一步阐明控制分子组织的原理，第二，利用这一点来表征较大片段的粘蛋白，第三，将其与抗体和半乳糖凝集素等其他分子的识别联系起来。CD43和CD45与Galectin-1的相互作用导致它们分离成不同的斑块，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，提供对这一过程的洞察和对自身免疫性疾病的可能控制。在肿瘤细胞上，这些糖蛋白以其异常的糖基化为特征，对其结构的了解有助于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.