Characterization of the heparan sulfate and chondroitin sulfate assembly sites in CD44
Characterization of the heparan sulfate and chondroitin sulfate assembly sites in CD44
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DOI：
10.1074/jbc.274.4.2511
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发表时间：
1999-01-22
影响因子：
4.8
通讯作者：
Bennett, KL
中科院分区：
文献类型：
--
作者：
Greenfield, B;Wang, WC;Bennett, KL
CD 44的同种型被糖胺聚糖（GAGs）、硫酸软骨素（CS）、硫酸乙酰肝素（HS）和硫酸角质素差异性地修饰。GAG组装发生在丝氨酸，然后是甘氨酸（SG），但并非所有SG都被利用。七个SG基序分布在5个CD 44外显子，在本文中，我们确定了HS和CS的组装位点，利用CD 44。没有所有的CD 44 SG位点都被修饰。CD 44外显子V3中的SGSG基序是唯一的HS组装位点;该位点也被CS修饰，该位点的HS和CS附着通过将V3基序中的丝氨酸突变为丙氨酸（AGAG）而消除，外显子E5是唯一的其他CD 44外显子支持GAG组装并被CS修饰。使用大量的重组CD 44蛋白片段，我们在此表明，位于V3中SGSG位点下游的8个氨基酸负责将HS特异性添加到该位点。如果位于⑶ 44外显子E5中的第一SIG位点下游的八个氨基酸与位于外显子V3中的SGSG位点下游的那些氨基酸交换，则E5中的SG位点变为被HS和CS修饰。同样地，如果在E5中的第一SG下游发现的八个氨基酸位于V3中的SGSG下游，则该位点被CS而不是HS修饰。我们还表明，这些序列不能直接修改CD 44与HS从远处。含有⑶ 44外显子V3的构建体（其中SGSG基序突变为AGAG）不用HS修饰，即使它们含有其他SG基序。因此，已经鉴定了决定⑶ 44上的GAG合成的许多序列和结构要求。
Isoforms of CD44 are differentially modified by the glycosaminoglycans (GAGs) chondroitin sulfate (CS), heparan sulfate (HS), and keratan sulfate. GAG assembly occurs at serines followed by glycines (SG), but not all SG are utilized. Seven SG motifs are distributed in five CD44 exons, and in this paper we identify the HS and CS assembly sites that are utilized in CD44. Not. all the CD44 SG sites are modified. The SGSG motif in CD44 exon V3 is the only HS assembly site; this site is also modified with CS, HS and CS attachment at that site was eliminated by mutation of the serines in the V3 motif to alanine (AGAG), Exon E5 is the only other CD44 exon that supports GAG assembly and is modified with CS. Using a number of recombinant CD44 protein fragments we show herein that the eight amino acids located downstream of the SGSG site in V3 are responsible for the specific addition of HS to this site. If the eight amino acids located downstream from the first SIG site in CD44 exon E5 are exchanged with those located downstream of the SGSG site in exon V3, the SG site in E5 becomes modified with HS and CS, Likewise if the eight amino acids found downstream from the first SG in E5 are placed downstream from the SGSG in V3, this site is modified with CS but not HS. We also show that these sequences cannot direct the modification of CD44 with; HS from a distance. Constructs containing CD44 exon V3 in which the SGSG motif was mutated to AGAG were not modified with HS even though they contained other SG motifs. Thus, a number of sequence and structural requirements that dictate GAG synthesis on CD44 have been identified.