Esford L E, Maiti A, Bader S A, Tufaro F, Johnson P
Department of Microbiology, University of British Columbia, Vancouver, B.C. V6T 1Z3, Canada.
J Cell Sci. 1998 Apr;111 ( Pt 7):1021-9. doi: 10.1242/jcs.111.7.1021.
CD44 is a widely expressed cell adhesion molecule that binds the extracellular matrix component, hyaluronan, in a tightly regulated manner. Previous studies have shown that the CD44-hyaluronan interaction is affected by changes in the glycosylation state of CD44. In this study, we take advantage of several well-characterized murine L cell mutants defective in heparan sulfate synthesis (gro2C cells), heparan sulfate and chondroitin sulfate synthesis (sog9 cells), and glycosaminoglycan and oligosaccharide processing (sog8 cells) to assess the effects of these defects on the hyaluronan binding ability of CD44. In parental L cells and gro2C cells, CD44 was induced to bind hyaluronan after addition of the activating, anti-CD44 monoclonal antibody, IRAWB 14. By contrast, no inducible binding was observed in sog9 cells. Treatment of L cells with sodium chlorate, an inhibitor of sulfation, also abolished inducible hyaluronan binding. However, inducible and some constitutive hyaluronan binding was observed in sog8 cells. This indicates that sulfation and, in particular, the addition of chondroitin sulfate are required for inducible hyaluronan binding by CD44 in L cells. However, in the absence of fully processed oligosaccharides, chondroitin sulfate is not essential for hyaluronan binding, indicating that the effect of chondroitin sulfate is dependent upon the glycosylation state of the cell. Thus, in addition to glycosylation, chondroitin sulfate biosynthesis is an important post-translational modification that can affect the hyaluronan binding ability of CD44.
CD44是一种广泛表达的细胞粘附分子，它以严格调控的方式结合细胞外基质成分透明质酸。先前的研究表明，CD44与透明质酸的相互作用受CD44糖基化状态变化的影响。在本研究中，我们利用了几种特性明确的小鼠L细胞突变体，这些突变体在硫酸乙酰肝素合成方面存在缺陷（gro2C细胞）、在硫酸乙酰肝素和硫酸软骨素合成方面存在缺陷（sog9细胞）以及在糖胺聚糖和寡糖加工方面存在缺陷（sog8细胞），以评估这些缺陷对CD44透明质酸结合能力的影响。在亲本L细胞和gro2C细胞中，添加激活型抗CD44单克隆抗体IRAWB 14后，CD44被诱导结合透明质酸。相比之下，在sog9细胞中未观察到诱导性结合。用硫酸化抑制剂氯酸钠处理L细胞也消除了诱导性透明质酸结合。然而，在sog8细胞中观察到了诱导性和一些组成性透明质酸结合。这表明硫酸化，尤其是硫酸软骨素的添加，是L细胞中CD44诱导性透明质酸结合所必需的。然而，在缺乏完全加工的寡糖的情况下，硫酸软骨素对于透明质酸结合并非必不可少，这表明硫酸软骨素的作用取决于细胞的糖基化状态。因此，除了糖基化之外，硫酸软骨素生物合成是一种重要的翻译后修饰，可影响CD44的透明质酸结合能力。
