Protein-Specific Polysialylation

描述(由申请人提供)：存在长链的α2， 细胞表面糖蛋白上的8-聚唾液酸对细胞的负性调节作用 通过防止细胞彼此紧密相对而产生的粘连。在.期间 发育，PSA在轴突引导、轴突寻路和细胞中的作用 迁移。在成年动物中，它的表达持续存在于大脑的各个区域 需要形态功能可塑性，并且在各种癌症中重新表达 被认为对其高度转移行为有贡献的细胞。 PSA是一种蛋白质特异性修饰，存在于一小群 包括神经细胞黏附分子(NCAM)的蛋白质，a亚单位 以及多唾液酸转移酶PST和PST STX.是什么引导多唾液酸基转移酶识别特定的 糖蛋白尚不清楚。我们假设聚唾液酸基转移酶 识别糖蛋白的某些氨基酸序列或结构特征 底物，并且这种最初的蛋白质-蛋白质相互作用允许 低聚糖的特异性聚唾液酸解。在这项建议的第一个目标中 我们将阐明介导NCAM多唾液酸化的蛋白质信号。我们有 确定了两种聚唾液酸转移酶，PST和STX，是 在细胞内自聚唾液。在这项提议的第二个目标中，我们将 研究酶的自溶过程以及酶是如何 PST的自聚影响NCAM的聚唾液酸化。我们证明了这一点 人乳腺癌MCF7细胞株和RBL大鼠嗜碱性白血病细胞株 表达高水平的PSA和PST，但不表达NCAM或钠通道。我们 假设在这些细胞中检测到的PSA正在修改内源性PST。 在第三个特定目标中，我们将确定什么是多唾液酸化蛋白质 以检验自聚唾液酸化的PST是 在适当的级别和位置表达，以影响 这些细胞。这些研究和未来研究的总体目标是了解 蛋白质特异性多唾液酸化的机制及PSA在其中的作用 它修饰的蛋白质的功能。

DESCRIPTION (provided by applicant): The presence of long chains of alpha2, 8-polysialic acid (PSA) on cell surface glycoproteins negatively modulates cell adhesion by preventing cells from closely apposing one another. During development, PSA functions in axon guidance, axon pathfinding and cell migration. In the adult animal, its expression persists in areas of the brain requiring morphofunctional plasticity, and it is re-expressed in various cancer cells where it is thought to contribute to their highly metastatic behavior. PSA is a protein-specific modification that is found on a small group of proteins that includes the neural cell adhesion molecule (NCAM), the a subunit of the voltage-dependent sodium channel, and the polysialyltransferases PST and STX. What directs the polysialyltransferases to recognize specific glycoproteins is not known. We hypothesize that the polysialyltransferases recognize some amino acid sequence or structural feature of the glycoprotein substrate, and that this initial protein-protein interaction allows the specific polysialylation of oligosaccharides. In the first aim of this proposal we will elucidate the protein signals mediating NCAM polysialylation. We have established that the two polysialyltransferases, PST and STX, are autopolysialylated in cells. In the second aim of this proposal we will investigate the process of enzyme autopolysialylation and how the autopolysialylation of PST impacts NCAM polysialylation. We demonstrated that the MCF7 human breast carcinoma line and the RBL rat basophilic leukemia line express high levels of PSA and PST, but not NCAM or the sodium channel. We hypothesize that the PSA detected in these cells is modifying endogenous PST. In the third specific aim, we will determine what polysialylated proteins are present in these cells to test the hypothesis that autopolysialylated PST is expressed at appropriate levels and locations to impact the interactions of these cells. The overall goal of these and future studies is to understand the mechanism of protein-specific polysialylation and the role that PSA plays in the function of the proteins it modifies.