A role for cathepsin E in the processing of mast-cell carboxypeptidase A
A role for cathepsin E in the processing of mast-cell carboxypeptidase A
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DOI：
10.1242/jcs.02333
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发表时间：
2005-05-01
影响因子：
4
通讯作者：
Pejler, G
中科院分区：
文献类型：
--
作者：
Henningsson, F;Yamamoto, K;Pejler, G
在肥大细胞脱粒时，与一系列其他炎症介质一起释放。羧基肽酶A，像所有肥大细胞蛋白酶一样，作为一种活性酶（即去除前肽）储存在颗粒中。尽管其他种类的肥大细胞蛋白酶（尤其是乳糜酶）的加工机制已经在一定程度上得到了阐明，但对原羧肽酶A的加工机制却知之甚少。在这里，我们发现缺乏天冬氨酸蛋白酶组织蛋白酶E的小鼠肥大细胞显示出原羧肽酶A的积累，表明羧肽酶A加工的缺陷。相比之下，缺乏组织蛋白酶B、L或D的肥大细胞具有正常的羧肽酶- a加工。此外，重组组织蛋白酶E被发现在体外处理重组原羧肽酶A，条件类似于肥大细胞颗粒。免疫组织化学分析显示，正常小鼠肥大细胞中有组织蛋白酶E染色，而缺乏肝素的小鼠肥大细胞中没有，表明组织蛋白酶E与肥大细胞颗粒内的肝素蛋白聚糖结合。根据这一观点，亲和层析显示重组组织蛋白酶E在酸性条件下（肥大细胞颗粒中普遍存在的条件）与肝素强烈结合，而在中性ph下则不会。此外，肥大细胞脱粒导致组织蛋白酶E的释放。综合来看，我们的结果表明，组织蛋白酶E与肝素蛋白聚糖复合物位于肥大细胞分泌颗粒中。并且它在原羧肽酶a转化为活性蛋白酶的过程中起作用。
granule and is released, together with a range of other inflammatory mediators, upon mast-cell degranulation. Carboxypeptidase A, like all mast-cell proteases, is stored in the granule as an active enzyme (i.e. with its propeptide removed). Although the processing mechanisms for the other classes of mast-cell proteases (in particular the chymases) have been clarified to some extent, the processing of procarboxypeptidase A is poorly characterized. Here, we show that mast cells from mice lacking the aspartic protease cathepsin E display an accumulation of procarboxypeptidase A, indicating a defect in carboxypeptidase-A processing. By contrast, mast cells lacking cathepsins B, L or D have normal carboxypeptidase-A processing. Furthermore, recombinant cathepsin E was found to process recombinant procarboxypeptidase A in vitro, under conditions resembling those found in mast-cell granules. Immunohistochemical analysis revealed staining for cathepsin E in mast cells from normal mice but not in mast cells from mice lacking heparin, indicating that cathepsin E is bound to heparin proteoglycan within mast-cell granules. In accordance with this notion, affinity chromatography showed that recombinant cathepsin E bound strongly to heparin under acidic conditions (the conditions prevailing in mast-cell granules) but not at neutral pH. Moreover, mast-cell degranulation resulted in the release of cathepsin E. Taken together, our results indicate that cathepsin E is located in mast-cell secretory granules in complex with heparin proteoglycans, and that it has a role in the processing of procarboxypeptidase A into active protease.