Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
Int Immunol. 2010 Aug;22(8):637-49. doi: 10.1093/intimm/dxq048. Epub 2010 May 25.
Polymorphonuclear neutrophils (PMNs) are the first line of defense against invading organisms in humans; in addition, PMNs contribute to the linking of innate and adaptive immunity. To fulfill their biological behavior, PMNs utilize an arsenal of proteolytic enzymes, including members of the matrix metalloproteinase family of zinc-dependent endopeptidases. PMNs express high levels of MT6-MMP (MMP-25), a glycosyl-phosphatidylinositol-anchored MMP, that belongs to the subfamily of membrane-anchored matrix metalloproteinases. Due to the paucity of information on MT6-MMP in primary cells, we set to investigate the localization and potential function of MT6-MMP in human PMNs. We found that MT6-MMP is present in the membrane, granules and nuclear/endoplasmic reticulum/Golgi fractions of PMNs where it is displayed as a disulfide-linked homodimer of 120 kDa. Stimulation of PMNs resulted in secretion of active MT6-MMP into the supernatants. Membrane-bound MT6-MMP, conversely, is located in the lipid rafts of resting PMNs and stimulation does not alter this location. In addition, TIMP-2, a natural inhibitor of MT6-MMP, does not co-localize with it in the lipid rafts. Interestingly, living PMNs do not display MT6-MMP on the cell surface. However, induction of apoptosis induces MT6-MMP relocation on PMNs' cell surface. Our studies suggest that metalloproteinases may play a role in respiratory burst and IL-8 secretion, but not chemotaxis or granulocyte macrophage colony-stimulating factor-induced survival. Collectively, these results provide new insights on the role of MT6-MMP in the physiology of human PMNs.
多形核粒细胞(PMN)是人体抵御入侵生物的第一道防线;此外,PMN 有助于先天免疫和适应性免疫的联系。为了实现其生物学行为,PMN 利用了一系列的蛋白水解酶,包括基质金属蛋白酶家族的锌依赖性内肽酶成员。PMN 表达高水平的 MT6-MMP(MMP-25),一种糖基磷脂酰肌醇锚定的 MMP,属于膜锚定基质金属蛋白酶亚家族。由于关于原代细胞中 MT6-MMP 的信息很少,我们着手研究 MT6-MMP 在人 PMN 中的定位和潜在功能。我们发现 MT6-MMP 存在于 PMN 的膜、颗粒和核/内质网/高尔基体部分,在那里它显示为 120 kDa 的二硫键连接同源二聚体。PMN 的刺激导致活性 MT6-MMP 分泌到上清液中。相反,膜结合的 MT6-MMP 位于静止 PMN 的脂筏中,刺激不会改变这种位置。此外,MT6-MMP 的天然抑制剂 TIMP-2 不在脂筏中与它共定位。有趣的是,活 PMN 不在其细胞表面显示 MT6-MMP。然而,诱导细胞凋亡诱导 MT6-MMP 在 PMN 细胞表面的重新定位。我们的研究表明,金属蛋白酶可能在呼吸爆发和 IL-8 分泌中发挥作用,但在趋化性或粒细胞巨噬细胞集落刺激因子诱导的存活中不起作用。总的来说,这些结果提供了关于 MT6-MMP 在人 PMN 生理学中的作用的新见解。