Protein-Specific Polysialylation

说明（由申请人提供）：α 2长链的存在， 8-细胞表面糖蛋白上的多聚唾液酸（PSA）负性调节细胞 通过防止细胞彼此紧密贴壁来粘附。期间 发育，PSA在轴突导向、轴突寻路和细胞增殖中的作用 迁移在成年动物中，它的表达持续存在于大脑的区域中， 需要形态功能可塑性，并且在各种癌症中重新表达 细胞，它被认为有助于他们的高转移性行为。 PSA是一种蛋白质特异性修饰，存在于一小群人的前列腺中。 包括神经细胞粘附分子（NCAM）、α亚基 的电压依赖性钠通道，和聚唾液酸转移酶PST和 STX。是什么引导聚唾液酸转移酶识别特定的 糖蛋白是未知的。我们假设聚唾液酸转移酶 识别糖蛋白的某些氨基酸序列或结构特征 底物，并且这种初始的蛋白质-蛋白质相互作用允许 寡糖的特异性聚唾液酸化。本提案的第一个目的是 我们将阐明介导NCAM多聚唾液酸化的蛋白信号。我们有 确定了两种多聚唾液酸转移酶PST和STX， 在细胞中自我解唾液酸化。在本提案的第二个目标中，我们将 研究酶自聚唾液酸化的过程以及 PST的自聚唾液酸化影响NCAM聚唾液酸化。我们证明了 MCF 7人乳腺癌细胞系和RBL大鼠嗜碱性白血病细胞系 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正在修饰内源性PST。 在第三个具体目标中，我们将确定什么是聚唾液酸化蛋白质 存在于这些细胞中，以检验自聚唾液酸化的PST是 在适当的级别和地点表达，以影响 这些细胞。这些和未来研究的总体目标是了解 蛋白质特异性聚唾液酸化的机制以及PSA在 它所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.