Dumermuth Eric, Beuret Nicole, Spiess Martin, Crottet Pascal
Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
J Biol Chem. 2002 May 24;277(21):18687-93. doi: 10.1074/jbc.M109408200. Epub 2002 Mar 19.
9-O-Acetylation of sialic acid is known as a cell type-specific modification of secretory and plasma membrane glycoconjugates of higher vertebrates with important functions in modulating cell-cell recognition. Using a recombinant probe derived from influenza C virus hemagglutinin, we discovered 9-O-acetylated protein in the Golgi complex of various cell lines, most of which did not display 9-O-acetylated sialic acid on the cell surface. All cell lines expressed a sulfated glycoprotein of 50 kDa (sgp50) carrying 9-O-acetylated sialic acids, which was used as a model substrate. Like gp40, the major receptor for influenza C virus of Madin-Darby canine kidney I cells, sgp50 is 9-O-acetylated on O-linked glycans. However, gp40 was not 9-O-acetylated when expressed in Madin-Darby canine kidney II or COS-7 cells. The results demonstrate the existence of two 9-O-acetylation machineries for O-glycosylated proteins with distinct substrate specificities. The widespread occurrence of 9-O-acetylated protein in the Golgi furthermore suggests an additional intracellular role for this modification.
唾液酸的9-O-乙酰化是高等脊椎动物分泌性和质膜糖缀合物的一种细胞类型特异性修饰，在调节细胞间识别方面具有重要功能。利用源自丙型流感病毒血凝素的重组探针，我们在各种细胞系的高尔基体复合物中发现了9-O-乙酰化蛋白，其中大多数细胞系在细胞表面未显示9-O-乙酰化唾液酸。所有细胞系均表达一种携带9-O-乙酰化唾液酸的50 kDa硫酸化糖蛋白（sgp50），其用作模型底物。与Madin-Darby犬肾I细胞的丙型流感病毒主要受体gp40一样，sgp50在O-连接聚糖上发生9-O-乙酰化。然而，当在Madin-Darby犬肾II或COS-7细胞中表达时，gp40未发生9-O-乙酰化。结果表明存在两种具有不同底物特异性的O-糖基化蛋白9-O-乙酰化机制。此外，高尔基体中广泛存在的9-O-乙酰化蛋白表明这种修饰在细胞内还有其他作用。
