Sialic acid specificity of myelin-associated glycoprotein binding
Sialic acid specificity of myelin-associated glycoprotein binding
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DOI：
10.1074/jbc.272.2.1248
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发表时间：
1997-01-10
影响因子：
4.8
通讯作者：
Schnaar, RL
中科院分区：
文献类型：
--
作者：
Collins, BE;Yang, LJS;Schnaar, RL
髓鞘相关糖蛋白（MAG）是一种神经系统细胞粘附分子，是一种i型凝集素，与唾液化糖缀合物结合，包括具有特征结构决定因素的神经节苷脂(Yang， L. J.-S。， Zeller, c.b., Shaper, n.l., Kiso， M, Hasegawa， A., Shapiro, r.e., and Schnaar, r.l. (1996) Proc. Natl。学会科学。美国93,814-818)。利用瞬时转染表达MAG的COS-1猴肾成纤维细胞和稳定转染表达MAG的中国仓鼠卵巢（CHO）细胞两种细胞粘附系统，探讨MAG-神经节苷脂结合的结构特异性。两种细胞类型结合相同的神经节苷脂：GQ1b α (IV(3)NeuAc)，III(6)NuAc,II3(NeuAc)(2)Gg(4)Cer) > GT1b = GD1a > GM3 > GM1， GD1b和GQ1b（后者不支持粘附）。用神经氨酸酶预处理表达mag的细胞，可增强细胞与mag的结合。表达MAG的中国仓鼠卵巢细胞直接与神经节苷结合，在薄层色谱上分离，允许在混合物中检测MAG结合种。MAG最简单的神经节苷配体是含n -乙酰神经氨酸的GM3，而含n -糖基神经氨酸的GM3不支持粘附。n -乙酰神经氨酸残基的化学修饰（在GD1a上）取消了MAG的结合。唾液酸被轻度高碘酸氧化成相应的七碳（或八碳）唾液酸醛，就像进一步转化成相应的伯醇一样，可以消除MAG结合。通过乙基酯化、酰胺化或还原来消除阴离子电荷也可以消除mag介导的细胞粘附。这些数据表明，mag -神经节苷脂结合具有高度特异性，并定义了mag介导的细胞粘附到神经节苷脂的关键碳水化合物结构决定因素。
Myelin associated glycoprotein (MAG), a nervous system cell adhesion molecule, is an I-type lectin that binds to sialylated glycoconjugates, including gangliosides bearing characteristic structural determinants (Yang, L. J.-S., Zeller, C. B., Shaper, N. L., Kiso, M., Hasegawa, A., Shapiro, R. E., and Schnaar, R. L. (1996) Proc. Natl. Acad. Sci. U.S.A. 93, 814-818). Two cell adhesion systems, COS-1 monkey kidney fibroblasts transiently transfected to express MAG and Chinese hamster ovary (CHO) cells stably transfected to express MAG, were used to probe the structural specificity of MAG-ganglioside binding. Both cell types bound to the same gangliosides: GQ1b alpha (IV(3)NeuAc),III(6)NuAc,II3(NeuAc)(2)Gg(4)Cer) > GT1b = GD1a > GM3 > GM1, GD1b, and GQ1b (the latter do not support adhesion). Binding was enhanced by pretreatment of MAG-expressing cells with neuraminidase. MAG-expressing Chinese hamster ovary cells bound directly to gangliosides resolved on thin layer chromatograms, allowing detection of MAG binding species in a mixture. The simplest ganglioside ligand for MAG was GM3 bearing N-acetylneuraminic acid, whereas GM3 bearing N-glycolylneuraminic acid did not support adhesion. Chemical modifications of N-acetylneuraminic acid residues (on GD1a) abrogated MAG binding. Mild periodate oxidation of sialic acids to their corresponding seven carbon (or eight-carbon) sialic acid aldehydes abolished MAG binding, as did further conversion to the corresponding primary alcohols. Eliminating the anionic charge by ethyl esterification, amidation, or reduction also abolished MAG-mediated cell adhesion. These data demonstrate that MAG-ganglioside binding is highly specific and defines key carbohydrate structural determinants for MAG-mediated cell adhesion to gangliosides.