Uliana Andrea S, Giraudo Claudio G, Maccioni Hugo J F
Centro de Investigaciones en Química Biológica de Córdoba, CIQUIBIC (UNC-CONICET), Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
Traffic. 2006 May;7(5):604-12. doi: 10.1111/j.1600-0854.2006.00413.x.
Complex glycolipid synthesis is catalyzed by different glycosyltransferases resident of the Golgi complex. Most of them are type II membrane proteins comprising a lumenal, C-terminal domain linked to an N-terminal domain (Ntd) constituted by a short cytoplasmic tail (ct), a transmembrane, and a lumenal stem regions. They concentrate selectively in different sub-Golgi compartments, in an overlapped manner, acting in succession in the addition of sugars to acceptor glycolipids. The Ntds are sufficient to localize glycosyltransferases in the Golgi complex, but it is not clear whether they also confer selective concentration in sub-Golgi compartments. Here, we studied whether the Ntd of SialT2, localized in the proximal Golgi, and the one of GalNAcT, a trans/TGN Golgi-concentrated enzyme, concentrate reporter proteins in the corresponding sub-Golgi compartment. The sub-Golgi concentration of the Ntds fused to spectral variants of the GFP was determined in CHO-K1 cells from their behavior upon addition of brefeldin A. Fluorescence microscopy and subcellular fractionation showed that the SialT2 Ntd concentrates in a proximal sub-Golgi compartment - and that of GalNAcT in TGN elements. Exchanging the transmembrane region and the cts of SialT2 and GalNAcT indicates that information for proximal or distal Golgi concentration is associated with the cts.
复杂糖脂的合成由高尔基体复合物中的不同糖基转移酶催化。它们中的大多数是II型膜蛋白，由一个腔面的C末端结构域与一个由短细胞质尾巴（ct）、一个跨膜结构域和一个腔面茎区组成的N末端结构域（Ntd）相连。它们以重叠的方式选择性地集中在不同的高尔基体亚区室中，依次作用于将糖添加到受体糖脂上。Ntd足以将糖基转移酶定位在高尔基体复合物中，但尚不清楚它们是否也赋予在高尔基体亚区室中的选择性集中。在这里，我们研究了位于高尔基体近端的SialT2的Ntd以及一种集中在反式/反式高尔基体网络（TGN）的GalNAcT的Ntd是否能将报告蛋白集中在相应的高尔基体亚区室中。在CHO-K1细胞中，通过添加布雷菲德菌素A后绿色荧光蛋白（GFP）光谱变体融合的Ntd的行为来确定其在高尔基体亚区室中的浓度。荧光显微镜和亚细胞分级分离表明，SialT2的Ntd集中在高尔基体近端亚区室中，而GalNAcT的Ntd集中在TGN元件中。交换SialT2和GalNAcT的跨膜区域和细胞质尾巴表明，高尔基体近端或远端集中的信息与细胞质尾巴有关。
