Endomucin, a sialomucin expressed in high endothelial venules, supports L-selectin-mediated rolling
Endomucin, a sialomucin expressed in high endothelial venules, supports L-selectin-mediated rolling
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DOI：
10.1093/intimm/dxh128
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发表时间：
2004-09-01
影响因子：
4.4
通讯作者：
Miyasaka, M
中科院分区：
文献类型：
--
作者：
Kanda, H;Tanaka, T;Miyasaka, M
淋巴细胞归巢到淋巴结是由淋巴细胞和高内皮微静脉（HEVs）之间的短暂但特异性的相互作用调节的，其初始阶段主要由白细胞粘附分子L-选择素控制，L-选择素识别唾液粘蛋白核心蛋白上显示的硫酸化和唾液酸化O-连接寡糖。唾液粘蛋白之一，内粘蛋白，主要表达于多种组织的血管内皮细胞，包括淋巴结的HEV;然而，它是否作为L-选择素的配体发挥作用仍有待正式证明。在这里，我们表明，内粘蛋白剪接异构体a主要表达在III型HEV和MAdCAM-1（+）HEV中，如在非HEV型血管内皮细胞中所见。使用可溶性L-选择素的亲和纯化，我们发现HEV内粘蛋白被L-选择素反应性寡糖特异性修饰，并且可以结合L-选择素以及HEV特异性mAb MECA-79。我们的研究结果还表明，一个90-100 kDa的内粘蛋白种类优先装饰与L-选择素反应性糖链，而80 kDa的种类代表传统的形式在淋巴结中的非HEV型血管内皮细胞中表达。此外，表达内粘蛋白以及碳水化合物修饰酶[核心-2 β-1，6-N-乙酰葡糖胺基转移酶（C2 GnT）、α-1，3-岩藻糖基转移酶VII（FucTVII）和L-选择素配体磺基转移酶（LSST）]的特定组合的CHO细胞系在体外流动条件下显示L-选择素依赖性滚动。这些结果表明，当内粘蛋白是适当的修饰，由一组特定的糖基转移酶和磺基转移酶，它可以作为一个配体的L-选择素，并在HEV表达的内粘蛋白可能代表另一个唾液酸粘蛋白配体的L-选择素。
Lymphocyte homing to lymph nodes is regulated by transient but specific interactions between lymphocytes and high endothelial venules (HEVs), the initial phase of which is mainly governed by the leukocyte adhesion molecule L-selectin, which recognizes sulfated and sialylated O-linked oligosaccharides displayed on sialomucin core proteins. One of the sialomucin proteins, endomucin, is predominantly expressed in vascular endothelial cells of a variety of tissues including the HEVs of lymph nodes; however, whether it functions as a ligand for L-selectin remains to be formally proven. Here we show that the endomucin splice isoform a is predominantly expressed in Ill HEVs and MAdCAM-1(+) HEVs, as seen in non-HEV-type vascular endothelial cells. Using affinity purification with soluble L-selectin, we found that HEV endomucin is specifically modified with L-selectin-reactive oligosaccharides and can bind L-selectin as well as an HEV-specific mAb, MECA-79. Our results also indicated that a 90-100 kDa endomucin species is preferentially decorated with L-selectin-reactive sugar chains, whereas an 80 kDa species represents conventional forms expressed in non-HEV-type vascular endothelial cells in lymph nodes. Furthermore, a CHO cell line expressing endomucin together with a specific combination of carbohydrate-modifying enzymes [core-2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT), alpha-1,3-fucosyltransferase VII (FucTVII) and L-selectin ligand sulfotransferase (LSST)] showed L-selectin-dependent rolling under flow conditions in vitro. These results suggest that when endomucin is appropriately modified by a specific set of glycosyltransferases and a sulfotransferase, it can function as a ligand for L-selectin, and that the endomucin expressed in HEVs may represent another sialomucin ligand for L-selectin.