Salmi M, Jalkanen S
National Public Health Institute, Turku, Finland.
Eur J Immunol. 1995 Oct;25(10):2803-12. doi: 10.1002/eji.1830251014.
Vascular endothelium plays a pivotal role in controlling leukocyte extravasation from the blood into the tissues. Vascular adhesion protein-1 (VAP-1) is a novel endothelial cell molecule which mediates lymphocyte binding to the vascular lining (Salmi, M., and Jalkanen, S., Science 1992. 257:1407). In this study, we analyzed endothelial cell type-specific differences of VAP-1. In vivo, VAP-1 is a 90/170-kDa molecule which is mainly expressed on the lumenal surface and in cytoplasmic granules of peripheral lymph node-type postcapillary venules (high endothelial venules, HEV). In tonsil HEV, VAP-1 is modified with abundant sialic acids. VAP-1 is also detectable in the cytoplasm of human umbilical vein endothelial cells (HUVEC) and in an endothelial cell hybrid EaHy-926, although both cell types lack detectable surface VAP-1. Cultured endothelial cells do not express MECA-79-defined peripheral lymph node addressins either. VAP-1 was not translocated onto the endothelial cell surface after stimulation with multiple cytokines, mitogens or secretagogues which induced expression of other known endothelial adhesion molecules. Biochemical analyses revealed that VAP-1 is a approximately 180-kDa protein in these endothelial cell types. Digestions with neuraminidase, O-glycanase and N-glycanase, as well as treatment of cells with tunicamycin and benzyl-N-acetylgalactosaminide, did not alter the molecular mass of VAP-1 in EaHy-926. Pulse-chase experiments showed that VAP-1 is directly synthesized as a 180-kDa molecule without any detectable precursors. Thus, in cultured endothelial cells, VAP-1 is a 180-kDa protein which is devoid of post-translational modifications, and in particular, lacks the sialic acids crucial for the function of VAP-1 in tonsil vessels. Notably, the endothelial cell types commonly used as a model in studying lymphocyte-endothelial cell interactions lack surface expression of VAP-1 and peripheral node addressins, and hence are inherently of limited use in analyses of the initial adhesion of lymphocytes.
血管内皮在控制白细胞从血液外渗进入组织的过程中起着关键作用。血管黏附蛋白-1（VAP-1）是一种新型内皮细胞分子，可介导淋巴细胞与血管内膜结合（萨尔米，M.，和亚尔卡宁，S.，《科学》，1992年。257:1407）。在本研究中，我们分析了VAP-1在内皮细胞类型上的特异性差异。在体内，VAP-1是一种90/170 kDa的分子，主要表达于外周淋巴结型毛细血管后微静脉（高内皮微静脉，HEV）的管腔表面和细胞质颗粒中。在扁桃体HEV中，VAP-1带有丰富的唾液酸修饰。在人脐静脉内皮细胞（HUVEC）的细胞质以及内皮细胞杂交体EaHy-926中也可检测到VAP-1，尽管这两种细胞类型均未检测到表面VAP-1。培养的内皮细胞也不表达MECA-79定义的外周淋巴结地址素。在用多种细胞因子、丝裂原或促分泌剂刺激诱导其他已知内皮黏附分子表达后，VAP-1并未转位到内皮细胞表面。生化分析表明，在这些内皮细胞类型中，VAP-1是一种约180 kDa的蛋白质。用神经氨酸酶、O-聚糖酶和N-聚糖酶消化，以及用衣霉素和苄基-N-乙酰半乳糖胺处理细胞，均未改变EaHy-926中VAP-1的分子量。脉冲追踪实验表明，VAP-1直接合成时即为180 kDa的分子，没有任何可检测到的前体。因此，在培养的内皮细胞中，VAP-1是一种180 kDa的蛋白质，缺乏翻译后修饰，尤其是缺乏对扁桃体血管中VAP-1功能至关重要的唾液酸。值得注意的是，在研究淋巴细胞与内皮细胞相互作用时常用作模型的内皮细胞类型缺乏VAP-1和外周淋巴结地址素的表面表达，因此在分析淋巴细胞的初始黏附时其用途有限。
