Functional Organization of Golgi N- and O-Glycosylation Pathways Involves pH-dependent Complex Formation That Is Impaired in Cancer Cells
Functional Organization of Golgi N- and O-Glycosylation Pathways Involves pH-dependent Complex Formation That Is Impaired in Cancer Cells
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DOI：
10.1074/jbc.m111.277681
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发表时间：
2011-11-04
影响因子：
4.8
通讯作者：
Kellokumpu, Sakari
中科院分区：
文献类型：
--
作者：
Hassinen, Antti;Pujol, Francois M.;Kellokumpu, Sakari
糖基化是蛋白质和脂质最常见的修饰之一，也是真核生物生物多样性的主要来源。它对许多基本的细胞功能和识别事件至关重要，从蛋白质折叠到细胞信号传导，免疫防御和多细胞生物体的发育。糖基化主要发生在内质网和高尔基体中，涉及数十种功能不同的糖苷酶和糖基转移酶。这些酶的功能是如何协调的，以忠实地合成大量不同的聚糖结构，目前还不清楚。在这里，我们调查的超分子组织高尔基体N-和O-糖基化途径在活细胞中使用FRET流式细胞定量方法。我们表明，酶形成酶活性的同源和/或异源复合物内的每个途径。然而，没有检测到由在不同途径中操作的酶组成的复合物，这表明这些途径在物理上是不同的。此外，我们表明，复合物的形成几乎完全介导的相互作用的酶的催化结构域。我们的数据还表明，异聚体复合物的功能更重要的比酶同聚体。异聚体复合物的形成被认为是依赖于高尔基体的酸度，显着受损的酸化缺陷的癌细胞，并需要有效的细胞表面聚糖的合成。总的来说，这些结果强调高尔基体糖基化途径在功能上被组织成对聚糖合成很重要的复合物。
Glycosylation is one of the most common modifications of proteins and lipids and also a major source of biological diversity in eukaryotes. It is critical for many basic cellular functions and recognition events that range from protein folding to cell signaling, immunological defense, and the development of multicellular organisms. Glycosylation takes place mainly in the endoplasmic reticulum and Golgi apparatus and involves dozens of functionally distinct glycosidases and glycosyltransferases. How the functions of these enzymes, which act sequentially and often competitively, are coordinated to faithfully synthesize a vast array of different glycan structures is currently unclear. Here, we investigate the supramolecular organization of the Golgi N- and O-glycosylation pathways in live cells using a FRET flow cytometric quantification approach. We show that the enzymes form enzymatically active homo- and/or heteromeric complexes within each pathway. However, no complexes composed of enzymes that operate in different pathways, were detected, which suggests that the pathways are physically distinct. In addition, we show that complex formation is mediated almost exclusively by the catalytic domains of the interacting enzymes. Our data also suggest that the heteromeric complexes are functionally more important than enzyme homomers. Heteromeric complex formation was found to be dependent on Golgi acidity, markedly impaired in acidification-defective cancer cells, and required for the efficient synthesis of cell surface glycans. Collectively, the results emphasize that the Golgi glycosylation pathways are functionally organized into complexes that are important for glycan synthesis.