Seidenfaden R, Gerardy-Schahn R, Hildebrandt H
Institut für Zoologie, Universität Hohenheim, Stuttgart, Germany.
Eur J Cell Biol. 2000 Oct;79(10):680-8. doi: 10.1078/0171-9335-00093.
Polysialic acid (PSA) is a developmentally regulated carbohydrate consisting of alpha-2,8-linked sialic acid residues attached to the neural cell adhesion molecule NCAM. PSA promotes plasticity of cell-cell interactions in the nervous system and appears linked to the malignant potential of several tumors. Two enzymes, the polysialyltransferases ST8SiaII (STX) and ST8SiaIV (PST) have been identified and shown to be independently able to synthesize PSA. However, in vivo studies have demonstrated that in the majority of PSA-positive tissues the two polysialyltransferases are expressed simultaneously. Therefore, this study was undertaken to elucidate in which way the individual enzymes contribute to PSA expression under in vivo conditions. Using a semiquantitative RT-PCR strategy PSA-positive human tumor cell lines were screened for expression of ST8SiaII and ST8SiaIV at the mRNA level. Divergent patterns observed in some cell lines suggest that polysialyltransferases are independently regulated at the transcriptional level. In subsequent analyses the different mRNA levels of ST8SiaII and ST8SiaIV in these tumor cells were correlated with the degree of PSA expression and the cellular capacity to rapidly synthesize PSA. Our data indicate that ST8SiaIV is the major regulator of NCAM polysialylation in vivo.
多唾液酸（PSA）是一种在发育过程中受到调控的碳水化合物，由连接在神经细胞黏附分子NCAM上的α-2,8-连接的唾液酸残基组成。PSA促进神经系统中细胞间相互作用的可塑性，并且似乎与几种肿瘤的恶性潜能有关。已经鉴定出两种酶，即多唾液酸转移酶ST8SiaII（STX）和ST8SiaIV（PST），并表明它们能够独立合成PSA。然而，体内研究表明，在大多数PSA阳性组织中，这两种多唾液酸转移酶同时表达。因此，本研究旨在阐明在体内条件下，这两种酶以何种方式对PSA表达起作用。使用半定量RT-PCR策略，在mRNA水平上筛选PSA阳性的人肿瘤细胞系中ST8SiaII和ST8SiaIV的表达。在一些细胞系中观察到的不同模式表明，多唾液酸转移酶在转录水平上是独立调节的。在随后的分析中，这些肿瘤细胞中ST8SiaII和ST8SiaIV的不同mRNA水平与PSA表达程度以及细胞快速合成PSA的能力相关。我们的数据表明，ST8SiaIV是体内NCAM多唾液酸化的主要调节因子。
