Garton Kyle J, Gough Peter J, Philalay Julie, Wille Paul T, Blobel Carl P, Whitehead Robert H, Dempsey Peter J, Raines Elaine W
Department of Pathology, University of Washington, Harborview Medical Center, Seattle, Washington 98104-2499, USA.
J Biol Chem. 2003 Sep 26;278(39):37459-64. doi: 10.1074/jbc.M305877200. Epub 2003 Jul 23.
A variety of cell surface adhesion molecules can exist as both transmembrane proteins and soluble circulating forms. Increases in the levels of soluble adhesion molecules have been correlated with a variety of inflammatory diseases, suggesting a pathological role. Although soluble forms are thought to result from proteolytic cleavage from the cell surface, relatively little is known about the proteases responsible for their release. In this report we demonstrate that under normal culture conditions, cells expressing vascular cell adhesion molecule 1 (VCAM-1) release a soluble form of the extracellular domain that is generated by metalloproteinase-mediated cleavage. VCAM-1 release can be rapidly simulated by phorbol 12-myristate 13-acetate (PMA), and this induced VCAM-1 shedding is mediated by metalloproteinase cleavage of VCAM-1 near the transmembrane domain. PMA-induced VCAM-1 shedding occurs as the result of activation of a specific pathway, as the generation of soluble forms of three other adhesion molecules, E-selectin, platelet-endothelial cell adhesion molecule 1, and intercellular adhesion molecule 1, are not altered by PMA stimulation. Using cells derived from genetically deficient mice, we identify tumor necrosis factor-alpha-converting enzyme (TACE or ADAM 17) as the protease responsible for PMA-induced VCAM-1 release, including shedding of endogenously expressed VCAM-1 by murine endothelial cells. Therefore, TACE-mediated shedding of VCAM-1 may be important for the regulation of VCAM-1 function at the cell surface.
多种细胞表面黏附分子既可以以跨膜蛋白的形式存在，也可以以可溶性循环形式存在。可溶性黏附分子水平的升高与多种炎症性疾病相关，提示其具有病理作用。尽管可溶性形式被认为是由细胞表面的蛋白水解切割产生的，但对于负责其释放的蛋白酶却知之甚少。在本报告中，我们证明在正常培养条件下，表达血管细胞黏附分子1（VCAM-1）的细胞会释放一种细胞外结构域的可溶性形式，该形式是由金属蛋白酶介导的切割产生的。佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）可迅速模拟VCAM-1的释放，这种诱导的VCAM-1脱落是由跨膜结构域附近的金属蛋白酶对VCAM-1的切割介导的。PMA诱导的VCAM-1脱落是特定途径激活的结果，因为其他三种黏附分子E-选择素、血小板内皮细胞黏附分子1和细胞间黏附分子1的可溶性形式的产生不受PMA刺激的影响。利用来自基因缺陷小鼠的细胞，我们确定肿瘤坏死因子-α转化酶（TACE或ADAM 17）是负责PMA诱导的VCAM-1释放的蛋白酶，包括小鼠内皮细胞内源性表达的VCAM-1的脱落。因此，TACE介导的VCAM-1脱落可能对细胞表面VCAM-1功能的调节很重要。
