Regulation of CD44 binding to hyaluronan by glycosylation of variably spliced exons.
Regulation of CD44 binding to hyaluronan by glycosylation of variably spliced exons.
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DOI：
10.1083/jcb.131.6.1623
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发表时间：
1995-12
期刊：
影响因子：
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通讯作者：
Aruffo A
中科院分区：
文献类型：
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作者：
Bennett KL;Modrell B;Greenfield B;Bartolazzi A;Stamenkovic I;Peach R;Jackson DG;Spring F;Aruffo A
白细胞归巢受体CD 44的透明质酸（HA）结合功能（凝集素功能）受到严格调控。在这里，我们解决可能的机制，调节CD 44亚型特异性HA结合。用表达CD 44 H、CD 44 E的黑素瘤转染子或用CD 44 H和CD 44 E的可溶性免疫球蛋白融合物（CD 44 H-Rg、CD 44 E-Rg）的结合研究显示，尽管两种CD 44同种型都可以结合HA，但CD 44 H比CD 44 E更有效地结合HA。使用CD 44-Rg融合蛋白，我们发现CD 44 E中的剪接外显子V8-V10特异性地降低了CD 44的凝集素功能，而ICAM-1免疫球蛋白结构域对V8-V10的取代使结合恢复到与CD 44 H相当的水平。相反，当外显子V8-V10被替换为CD 34粘蛋白结构域时，CD 44与HA的结合非常弱，所述粘蛋白结构域被O-连接的聚糖严重修饰。在存在O-连接糖基化抑制剂的情况下，产生CD 44 E-Rg或孵育表达CD 44 E的转染子分别恢复了HA与CD 44 H-Rg的结合和与细胞表面CD 44 H水平的结合。我们的结论是，差异剪接提供了一个调节机制，CD 44凝集素的功能，这种效果是由于部分O-连接的碳水化合物部分，这是添加到Ser/Thr丰富的区域编码的CD 44外显子。选择性剪接导致蛋白质糖基化的变化，为凝集素活性的调节提供了一种新的机制。
The hyaluronan (HA)-binding function (lectin function) of the leukocyte homing receptor, CD44, is tightly regulated. Herein we address possible mechanisms that regulate CD44 isoform-specific HA binding. Binding studies with melanoma transfectants expressing CD44H, CD44E, or with soluble immunoglobulin fusions of CD44H and CD44E (CD44H-Rg, CD44E-Rg) showed that although both CD44 isoforms can bind HA, CD44H binds HA more efficiently than CD44E. Using CD44-Rg fusion proteins we show that the variably spliced exons in CD44E, V8-V10, specifically reduce the lectin function of CD44, while replacement of V8-V10 by an ICAM-1 immunoglobulin domain restores binding to a level comparable to that of CD44H. Conversely, CD44 bound HA very weakly when exons V8-V10 were replaced with a CD34 mucin domain, which is heavily modified by O- linked glycans. Production of CD44E-Rg or incubation of CD44E- expressing transfectants in the presence of an O-linked glycosylation inhibitor restored HA binding to CD44H-Rg and to cell surface CD44H levels, respectively. We conclude that differential splicing provides a regulatory mechanism for CD44 lectin function and that this effect is due in part to O-linked carbohydrate moieties which are added to the Ser/Thr rich regions encoded by the variably spliced CD44 exons. Alternative splicing resulting in changes in protein glycosylation provide a novel mechanism for the regulation of lectin activity.