Proteoglycan forms of the lymphocyte homing receptor CD44 are alternatively spliced variants containing the v3 exon.
Proteoglycan forms of the lymphocyte homing receptor CD44 are alternatively spliced variants containing the v3 exon.
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DOI：
10.1083/jcb.128.4.673
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发表时间：
1995-02
期刊：
影响因子：
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通讯作者：
Whittle N
中科院分区：
文献类型：
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作者：
Jackson DG;Bell JI;Dickinson R;Timans J;Shields J;Whittle N
CD 44细胞表面糖蛋白在广泛的不同组织中表达为多种同种型，含有1至10个插入胞外结构域的可变剪接外显子v1-v10。差异性糖基化产生更进一步的变异性，除了含有硫酸软骨素和硫酸乙酰肝素的蛋白聚糖样变体外，还产生N-和O-聚糖修饰形式的CD 44。这些高分子量的蛋白多糖样变异体，以前确定在淋巴细胞，黑色素瘤，角质形成细胞中涉及细胞-基质粘附，细胞运动性，和侵袭性。最近，推测携带糖胺聚糖链的单核细胞CD 44分子显示结合趋化因子MIP-1 β（Tanaka，Y.，D. H.亚当斯，S. Hubscher，H.平野大学Siebenlist和S.肖1993.自然（伦敦）。361：79-82.）提出了蛋白聚糖样CD 44变体可能在调节炎症反应中起作用的有趣的可能性。在这里，我们研究了这些蛋白聚糖样CD 44变体的分子身份，通过使用一种新的盒式克隆策略产生一组重组CD 44亚型。我们表明，软骨素和硫酸乙酰肝素修饰都与含有v3选择性外显子的亚型（CD 44 v3 -10和CD 44 v3，8-10）特异性相关，该外显子编码用于添加GAG的共有基序SGXG。其他同种型（CD 44 v10、CD 44 v8 - 10、CD 44 v7 -10和CD 44 v6 -10）显示缺乏这些GAG链，但携带广泛的O-聚糖修饰，最有可能在粘蛋白样选择性外显子插入物内。我们还证明，大多数内源性GAG修饰的CD 44亚型存在于上皮细胞构成V3亚型，从而建立在这些细胞中的蛋白聚糖样CD 44变体的大部分产生的选择性剪接。最后，我们使用转染的B淋巴瘤细胞证明，与CD 44 H不同，GAG修饰的CD 44亚型CD 44 v3 -10和CD 44 v3，8-10仅与透明质酸弱结合。连同随附论文中的演示（班尼特，K.，D. G.杰克逊，J.C.西蒙，E.坦佐斯河桃子，B。莫德雷尔岛Stamenkovic，G. Plowman和A.阿鲁福1995. 128：687-698），CD 44分子含有v3外显子结合生长因子，这些结果突出了一个新的和潜在的重要作用，CD 44可变剪接在控制细胞表面蛋白聚糖的表达。
The CD44 cell surface glycoprotein is expressed on a broad range of different tissues as multiple isoforms containing from one to ten alternatively spliced exons v1-v10 inserted within the extracellular domain. Differential glycosylation generates still further variability, yielding both N- and O-glycan-modified forms of CD44 in addition to proteoglycan-like variants containing chondroitin sulphate and heparan sulphate. These high molecular mass proteoglycan-like variants, previously identified in lymphocytes, melanomas, and keratinocytes have been implicated in cell-matrix adhesion, cell motility, and invasiveness. More recently, monocyte CD44 molecules presumed to carry glycosaminoglycan chains were shown to bind the chemokine MIP-1 beta (Tanaka, Y.,D. H. Adams, S. Hubscher, H. Hirano, U. Siebenlist, and S. Shaw. 1993. Nature (Lond). 361:79-82.) raising the intriguing possibility that proteoglycan-like CD44 variants might play a role in regulating inflammatory responses. Here we have investigated the molecular identity of these proteoglycan-like CD44 variants by generating a panel of recombinant CD44 isoforms using a novel cassette cloning strategy. We show that both chondroitin and heparan sulphate modifications are associated specifically with isoforms (CD44v3-10 and CD44v3,8-10) containing the v3 alternative exon which encodes a consensus motif SGXG for GAG addition. Other isoforms (CD44v10, CD44v8- 10, CD44v7-10, and CD44v6-10) are shown to lack these GAG chains but to carry extensive O-glycan modifications, most likely within the mucin- like alternative exon inserts. We also demonstrate that the majority of endogenous GAG-modified CD44 isoforms present in epithelial cells constitute v3 isoforms thus establishing that in these cells the majority of proteoglycan-like CD44 variants are generated by alternative splicing. Finally we present evidence using transfected B lymphoma cells that the GAG-modified CD44 isoforms CD44v3-10 and CD44v3,8-10, unlike CD44H, bind only weakly to hyaluronan. Together with the demonstration in the accompanying paper (Bennett, K., D. G. Jackson, J.C. Simon, E. Tanczos, R. Peach, B. Modrell, I. Stamenkovic, G. Plowman, and A. Aruffo. 1995. J. Cell Biol. 128:687-698.), that CD44 molecules containing the v3 exon bind growth factors, these results highlight a new and potentially important role for CD44 alternative splicing in the control of cell-surface proteoglycan expression.