Department of Anatomy, Physiology, and Biochemistry, Swedish University of Agricultural Sciences, 75123 Uppsala, Sweden;
J Immunol. 2013 Oct 1;191(7):3931-8. doi: 10.4049/jimmunol.1301441. Epub 2013 Aug 23.
Mast cells are characterized by an abundance of secretory granules densely packed with inflammatory mediators such as bioactive amines, cytokines, serglycin proteoglycans with negatively charged glycosaminoglycan side chains of either heparin or chondroitin sulfate type, and large amounts of positively charged proteases. Despite the large biological impact of mast cell granules and their contents on various pathologies, the mechanisms that regulate granule composition are incompletely understood. In this study, we hypothesized that granule composition is dependent on a dynamic electrostatic interrelationship between different granule compounds. As a tool to evaluate this possibility, we generated mice in which mast cells are multideficient in a panel of positively charged proteases: the chymase mouse mast cell protease-4, the tryptase mouse mast cell protease-6, and carboxypeptidase A3. Through a posttranslational effect, mast cells from these mice additionally lack mouse mast cell protease-5 protein. Mast cells from mice deficient in individual proteases showed normal morphology. In contrast, mast cells with combined protease deficiency displayed a profound distortion of granule integrity, as seen both by conventional morphological criteria and by transmission electron microscopy. An assessment of granule content revealed that the distorted granule integrity in multiprotease-deficient mast cells was associated with a profound reduction of highly negatively charged heparin, whereas no reduction in chondroitin sulfate storage was observed. Taken together with previous findings showing that the storage of basic proteases conversely is regulated by anionic proteoglycans, these data suggest that secretory granule composition in mast cells is dependent on a dynamic interrelationship between granule compounds of opposite electrical charge.
肥大细胞的特征是含有大量的分泌颗粒，这些颗粒中充满了炎症介质，如生物活性胺、细胞因子、带有负电荷糖胺聚糖侧链的糖胺聚糖蛋白聚糖，以及大量的正电荷蛋白酶。尽管肥大细胞颗粒及其内容物对各种病理状态具有巨大的生物学影响，但调节颗粒组成的机制尚不完全清楚。在这项研究中，我们假设颗粒组成依赖于不同颗粒化合物之间动态的静电相互关系。作为评估这种可能性的工具，我们生成了一组缺乏多种正电荷蛋白酶的肥大细胞缺失型小鼠：糜酶（chymase）小鼠肥大细胞蛋白酶-4、类胰蛋白酶（tryptase）小鼠肥大细胞蛋白酶-6 和羧肽酶 A3。通过翻译后效应，这些小鼠的肥大细胞还缺乏小鼠肥大细胞蛋白酶-5 蛋白。缺乏单个蛋白酶的肥大细胞表现出正常的形态。相比之下，缺乏多种蛋白酶的肥大细胞显示出颗粒完整性的严重扭曲，这既可以通过传统的形态学标准，也可以通过透射电子显微镜观察到。对颗粒内容物的评估表明，在多蛋白酶缺乏型肥大细胞中，扭曲的颗粒完整性与高度带负电荷的肝素的严重减少有关，而硫酸软骨素的储存没有减少。结合先前的研究结果，表明碱性蛋白酶的储存反过来受到阴离子蛋白聚糖的调节，这些数据表明肥大细胞的分泌颗粒组成依赖于相反电荷的颗粒化合物之间的动态相互关系。
