Mori Airi, Hane Masaya, Niimi Yuki, Kitajima Ken, Sato Chihiro
Bioscience and Biotechnology Center.
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
Glycobiology. 2017 Sep 1;27(9):834-846. doi: 10.1093/glycob/cwx057.
Polysialic acid (polySia) is mainly found as a modification of neural cell adhesion molecule (NCAM) in whole embryonic brains, as well as restricted areas of adult vertebrate brains, including the hippocampus. PolySia shows not only repulsive effects on NCAM-involved cell-cell interactions due to its bulky and hydrated properties, but also attractive effects on the interaction with neurologically active molecules, which exerts a reservoir function. Two different polysialyltransferases, ST8SIA2 and ST8SIA4, are involved in the synthesis of polySia chains; however, to date, the differences of the properties between polySia chains synthesized by these two enzymes remain unknown. In this study, to clarify this point, we first prepared polySia-NCAMs from HEK293 cells stably expressing ST8SIA4 and ST8SIA2, or ST8SIA2 (SNP-7), a mutant ST8SIA2 derived from a schizophrenia patient. The conventional sensitive chemical and immunological characterizations showed that the quantity and quality (structural features) of polySia are not so much different between ST8SIA4- and ST8SIA2-synthesized ones, apart from those of ST8SIA2 (SNP-7). Then, we assessed the homophilic and heterophilic interactions mediated by polySia-NCAM by adopting a surface plasmon resonance measurement as an in vitro analytical method. Our novel findings are as follows: (i) the ST8SIA2- and ST8SIA4-synthesized polySia-NCAMs exhibited different attractive and repulsive effects than each other; (ii) both polySia- and oligoSia-NCAMs synthesized by ST8SIA2 were able to bind polySia-NCAMs; (iii) the polySia-NCAM synthesized by a ST8SIA2 (SNP-7) showed markedly altered attractive and repulsive properties. Collectively, polySia-NCAM is suggested to simultaneously possess both attractive and repulsive properties that are highly regulated by the two polysialyltransferases.
多唾液酸（polySia）主要作为神经细胞黏附分子（NCAM）的修饰物存在于整个胚胎大脑以及成年脊椎动物大脑的特定区域，包括海马体。由于其庞大且具有水合性的特性，polySia不仅对涉及NCAM的细胞间相互作用具有排斥作用，还对与神经活性分子的相互作用具有吸引作用，发挥着一种储存功能。两种不同的多唾液酸转移酶，ST8SIA2和ST8SIA4，参与了polySia链的合成；然而，迄今为止，由这两种酶合成的polySia链之间性质的差异仍不清楚。在本研究中，为了阐明这一点，我们首先从稳定表达ST8SIA4和ST8SIA2或ST8SIA2（SNP - 7，一种源自精神分裂症患者的ST8SIA2突变体）的HEK293细胞中制备了polySia - NCAM。传统的灵敏化学和免疫表征表明，除了ST8SIA2（SNP - 7）合成的polySia外，ST8SIA4和ST8SIA2合成的polySia在数量和质量（结构特征）上并没有太大差异。然后，我们采用表面等离子体共振测量作为体外分析方法，评估了由polySia - NCAM介导的同源和异源相互作用。我们的新发现如下：（i）由ST8SIA2和ST8SIA4合成的polySia - NCAM表现出彼此不同的吸引和排斥作用；（ii）由ST8SIA2合成的polySia - NCAM和寡唾液酸 - NCAM都能够结合polySia - NCAM；（iii）由ST8SIA2（SNP - 7）合成的polySia - NCAM表现出明显改变的吸引和排斥特性。总体而言，polySia - NCAM被认为同时具有吸引和排斥特性，且这些特性受到两种多唾液酸转移酶的高度调控。
