Heparan sulfate biosynthesis enzymes EXT1 and EXT2 affect NDST1 expression and heparan sulfate sulfation
Heparan sulfate biosynthesis enzymes EXT1 and EXT2 affect NDST1 expression and heparan sulfate sulfation
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DOI：
10.1073/pnas.0705807105
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发表时间：
2008-03-25
影响因子：
11.1
通讯作者：
Kjellen, Lena
中科院分区：
文献类型：
--
作者：
Presto, Jenny;Thuveson, Maria;Kjellen, Lena
硫酸乙酰肝素（HS）蛋白聚糖影响胚胎发育和成人生理。通过与蛋白质配体的相互作用。相互作用取决于HIS结构，这在很大程度上是由高尔基体酶的生物合成过程中决定的。生物合成是如何被调节的，或多或少是未知的。在HIS链的聚合过程中，由外生骨素蛋白EXT 1和EXT 2的复合物进行，第一个修饰酶，葡糖胺基N-脱乙酰基酶/N-磺基转移酶（NDST），将N-硫酸酯基团引入到生长的聚合物中。出乎意料的是，我们发现EXT 1和EXT 2的表达水平影响了细胞中存在的NDST 1的量，这反过来又极大地影响了HIS结构。而EXT 2在HEK 293细胞中的过表达增强NDST 1表达，增加NDST 1 N-糖基化，并导致HIS硫酸化升高，EXT 1的过表达具有相反的作用。因此，来自过表达EXT 2的转基因小鼠的心脏组织显示出增加的NDST活性。免疫沉淀实验表明，EXT 2和NDST 1之间的相互作用。我们推测NDST 1与EXT 1竞争结合EXT 2。在成纤维细胞中增加的NDST活性与EXT 1中的基因陷阱突变支持这一观点。这些结果支持HS生物合成的酶形成复合物或GAGosome的模型。
Heparan sulfate (HS) proteoglycans influence embryonic development and adult physiology. through interactions with protein ligands. The interactions depend on HIS structure, which is determined largely during biosynthesis by Golgi enzymes. How biosynthesis is regulated is more or less unknown. During polymerization of the HIS chain, carried out by a complex of the exostosin proteins EXT1 and EXT2, the first modification enzyme, glucosaminyl N-deacetylase/N-sulfotransferase (NDST), introduces N-sulfate groups into the growing polymer. Unexpectedly, we found that the level of expression of EXT1 and EXT2 affected the amount of NDST1 present in the cell, which, in turn, greatly influenced HIS structure. Whereas overexpression of EXT2 in HEK 293 cells enhanced NDST1 expression, increased NDST1 N-glycosylation, and resulted in elevated HIS sulfation, overexpression of EXT1 had opposite effects. Accordingly, heart tissue from transgenic mice overexpressing EXT2 showed increased NDST activity. Immunoprecipitaion experiments suggested an interaction between EXT2 and NDST1. We speculate that NDST1 competes with EXT1 for binding to EXT2. Increased NDST activity in fibroblasts with a gene trap mutation in EXT1 supports this notion. These results support a model in which the enzymes of HS biosynthesis form a complex, or a GAGosome.