Mechanisms underlying preferential assembly of heparan sulfate on glypican-1
Mechanisms underlying preferential assembly of heparan sulfate on glypican-1
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DOI：
10.1074/jbc.m008283200
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发表时间：
2001-03-09
影响因子：
4.8
通讯作者：
Lander, AD
中科院分区：
文献类型：
--
作者：
Chen, RL;Lander, AD
磷脂酰肌醇蛋白聚糖是主要的细胞表面硫酸乙酰肝素蛋白聚糖，其结构特征在于存在富含半胱氨酸的球状结构域、短的糖胺聚糖（GAG）附着区和糖基磷脂酰肌醇膜锚。尽管glypicans的球状结构域具有很强的进化保守性，但还没有任何功能被归因于它们。通过使用一种新的定量方法来评估蛋白聚糖糖基化，我们在这里表明，从大鼠磷脂酰肌醇蛋白聚糖-1的球状结构域的去除将蛋白聚糖从一个类似于90%硫酸肝素（HS）的蛋白聚糖转化为一个类似于90%硫酸软骨素的蛋白聚糖。突变分析表明，序列至少70个氨基酸远离磷脂酰肌醇蛋白聚糖-1 GAG附着位点的优先HS组装所需的，虽然更多的附近的序列也发挥了作用。磷脂酰肌醇蛋白聚糖-1球状结构域对HS组装的影响也可以通过将该结构域与代表其他蛋白聚糖的GAG附着位点的序列融合来证明，或者令人惊讶的是，简单地通过在细胞中表达分离的球状结构域并分析对外源表达的磷脂酰肌醇蛋白聚糖1 GAG附着结构域或内源性蛋白聚糖的影响来证明。球状结构域对GAG除了蛋白聚糖核心蛋白的影响的定量分析表明，优先HS组装实现，至少部分地，通过抑制硫酸软骨素组装。这些数据将磷脂酰肌醇蛋白聚糖-1球状结构域鉴定为有效影响GAG类测定的结构基序，并表明磷脂酰肌醇蛋白聚糖球状结构域的重要作用是确保这些蛋白聚糖的高水平HS取代。
Glypicans are major cell surface heparan sulfate proteoglycans, the structures of which are characterized by the presence of a cysteine-rich globular domain, a short glycosaminoglycan (GAG) attachment region, and a glycosylphosphatidylinositol membrane anchor. Despite strong evolutionary conservation of the globular domains of glypicans, no function has yet been attributed to them. By using a novel quantitative approach for assessing proteoglycan glycosylation, we show here that removal of the globular domain from rat glypican-1 converts the proteoglycan from one that bears similar to 90% hepa ran sulfate (HS) to one that bears similar to 90% chondroitin sulfate. Mutational analysis shows that sequences at least 70 amino acids away from the glypican-1 GAG attachment site are required for preferential HS assembly, although more nearby sequences also play a role. The effects of the glypican-1 globular domain on HS assembly could also be demonstrated by fusing this domain to sequences representing the GAG attachment sites of other proteoglycans or, surprisingly, simply by expressing the isolated globular domain in cells and analyzing effects either on an exogenously expressed glypican l GAG; attachment domain or on endogenous proteoglycans. Quantitative analysis of the effect of the globular domain on GAG addition to proteoglycan core proteins suggested that preferential HS assembly is achieved, at least in part, through the inhibition of chondroitin sulfate assembly. These data identify the glypican-1 globular domain as a structural motif that potently influences GAG class determination and suggest that an important role of glypican globular domains is to ensure a high level of HS substitution of these proteoglycans.