Prydz Kristian, Simm Roger, Davydova Erna, Aasheim Hans-Christian
Section for Physiology and Cell Biology, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway.
Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway.
Glycobiology. 2025 Apr 23;35(6). doi: 10.1093/glycob/cwaf020.
The ephrin family of membrane proteins mediate intracellular signalling as ligands of transmembrane Eph tyrosine kinase receptors during cell-cell interactions. Ephrin/Eph signalling regulates processes like cell migration and angiogenesis and is of particular importance during embryonic development. Ephrins-A3 and -B3 can also bind to cell surface-associated and soluble heparan sulfate proteoglycans (HSPGs) that also play important roles during early development. Here we show that ephrins-B1, -B2, and -B3 all can bind in cis to cell surface HSPGs, while only ephrin-B1 interacts with cell surface HSPGs in a way that retards HSPG endocytosis. Expressing ephrin-B1 in HEK293T cells, using polyethyleneimine (PEI) as transfection agent, increased cell surface levels of HSPGs which were detected by an anti-heparan sulfate (HS) antibody or by ephrin-B3-Fc binding. Ephrin-B1 in the plasma membrane seemed to retard PEI-induced HSPG internalisation and degradation. Binding of HSPGs by ephrin-B1 was observed for the human, mouse, xenopus, and zebrafish homologs, and did not require the cytoplasmic tail of ephrin-B1 that contains tyrosines shown to be involved in intracellular signalling. Furthermore, ephrin-B1 could bind the HSPG variant of CD44 (CD44V3-10), a complex that could further associate with fibroblast growth factor receptors (1 and 4) after co-expression with one of these receptors. In summary, our data indicate that ephrin-B1 can regulate cellular HSPG turnover and is able to form complexes of potential biological importance with CD44V3-10 and fibroblast growth factor receptors.
膜蛋白 Ephrin 家族在细胞间相互作用过程中作为跨膜 Eph 酪氨酸激酶受体的配体介导细胞内信号传导。Ephrin/Eph 信号传导调节细胞迁移和血管生成等过程，在胚胎发育过程中尤为重要。Ephrins-A3 和 -B3 还可以与细胞表面相关的和可溶性硫酸乙酰肝素蛋白聚糖（HSPG）结合，这些蛋白聚糖在早期发育过程中也发挥着重要作用。在这里，我们表明 Ephrins-B1、-B2 和 -B3 都可以顺式结合到细胞表面 HSPG，而只有 Ephrin-B1 以一种减缓 HSPG 内吞作用的方式与细胞表面 HSPG 相互作用。使用聚乙烯亚胺（PEI）作为转染剂在 HEK293T 细胞中表达 Ephrin-B1，通过抗硫酸乙酰肝素（HS）抗体或 Ephrin-B3-Fc 结合检测到 HSPG 的细胞表面水平增加。质膜中的 Ephrin-B1 似乎减缓了 PEI 诱导的 HSPG 内化和降解。在人、小鼠、非洲爪蟾和斑马鱼的同源物中都观察到了 Ephrin-B1 与 HSPG 的结合，并且不需要 Ephrin-B1 含有已证明参与细胞内信号传导的酪氨酸的细胞质尾巴。此外，Ephrin-B1 可以结合 CD44 的 HSPG 变体（CD44V3-10），该复合物在与这些受体之一共表达后可以进一步与成纤维细胞生长因子受体（1 和 4）结合。总之，我们的数据表明 Ephrin-B1 可以调节细胞 HSPG 的周转，并能够与 CD44V3-10 和成纤维细胞生长因子受体形成具有潜在生物学重要性的复合物。
