Matrix assembly and homeostasis in collagen-rich tissues are mediated by interactions with proteoglycans (PGs) substituted with sulfated glycosaminoglycans (GAGs). The major GAG in cornea is keratan sulfate (KS), which is N-linked to one of three PG core proteins. To ascertain the importance of the carbohydrate chain sulfation step in KS functionality, we generated a strain of mice with a targeted gene deletion in Chst5, which encodes an N-acetylglucosamine-6-O-sulfotransferase that is integral to the sulfation of KS chains. Corneas of homozygous mutants were significantly thinner than those of WT or heterozygous mice. They lacked high-sulfated KS, but contained the core protein of the major corneal KSPG, lumican. Histochemically stained KSPGs coassociated with fibrillar collagen in WT corneas, but were not identified in the Chst5-null tissue. Conversely, abnormally large chondroitin sulfate/dermatan sulfate PG complexes were abundant throughout the Chst5-deficient cornea, indicating an alteration of controlled PG production in the mutant cornea. The corneal stroma of the Chst5-null mouse exhibited widespread structural alterations in collagen fibrillar architecture, including decreased interfibrillar spacing and a more spatially disorganized collagen array. The enzymatic sulfation of KS GAG chains is thus identified as a key requirement for PG biosynthesis and collagen matrix organization.

译文

:胶原蛋白丰富的组织中的基质组装和体内平衡是通过与被硫酸化的糖胺聚糖(GAG)取代的蛋白聚糖(PG)的相互作用而介导的。角膜中的主要GAG是硫酸角质素(KS),它与三种PG核心蛋白之一进行N-连接。为了确定碳水化合物链硫酸化步骤在KS功能中的重要性,我们生成了在Chst5中具有靶向基因缺失的小鼠品系,该菌株编码了KS链硫酸化所必需的N-乙酰氨基葡萄糖-6-O-磺基转移酶。纯合突变体的角膜明显比野生型或杂合小鼠的角膜薄。他们缺乏高硫酸盐化的KS,但含有主要角膜KSPG的核心蛋白lumican。组织化学染色的KSPG与野生型角膜中的原纤维胶原蛋白相关联,但在Chst5无组织中未发现。相反,在整个Chst5缺陷型角膜中,异常大的硫酸软骨素/硫酸皮肤素PG复合物丰富,表明突变体角膜中受控PG产生的改变。 Chst5-null小鼠的角膜基质在胶原纤维结构中表现出广泛的结构变化,包括减小的纤维间间距和空间上更混乱的胶原阵列。因此,KS GAG链的酶促硫酸化被确定为PG生物合成和胶原基质组织的关键要求。

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