The role of the propeptide for processing and sorting of human myeloperoxidase
The role of the propeptide for processing and sorting of human myeloperoxidase
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DOI：
10.1074/jbc.273.8.4747
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发表时间：
1998-02-20
影响因子：
4.8
通讯作者：
Olsson, I
中科院分区：
文献类型：
--
作者：
Andersson, E;Hellman, L;Olsson, I
髓过氧化物酶（MPO），储存在嗜中性粒细胞的嗜天青颗粒，是这些细胞的最佳氧依赖性杀微生物活性的关键。Pro-MPO经历逐步蛋白水解修剪，消除氨基末端前肽，产生一条重链和一条轻链多肽。MPO的前肽可能在新生蛋白质保留和折叠成其三级结构中或在靶向MPO前体用于颗粒中的加工和储存中起作用。构建前肽缺失的MPO前体突变体（MPO Delta pro）以确定前肽的缺失是否干扰转染至髓样32 D细胞系后的加工和靶向。人MPO全长cDNA的转染导致MPO的正常加工和靶向细胞质致密细胞器。虽然MPO Delta pro的掺入效率较低，但pro-MPO和MPO Delta pro均显示血红素掺入，表明前肽对该过程并不重要。前肽的缺失导致蛋白质的合成，所述蛋白质缺乏加工成成熟的双链形式，而是在细胞内降解或分泌。在溶酶体营养剂或布雷菲德菌素A存在下MPO δ原的持续降解的发现排除了所观察到的降解发生在转移到颗粒之后。细胞内MPO原具有高甘露糖寡糖侧链，而通过对糖苷内切酶H的部分敏感性判断，发现储存的成熟MPO具有高甘露糖和复杂的寡糖侧链。前肽通常可干扰某些复杂寡糖链的产生，这一点得到了分泌型MPO前体中高甘露糖侧链的发现以及仅含有复杂寡糖侧链的MPO Delta pro中缺乏甘露糖侧链的发现的支持。总之，前MPO的前肽的消除阻断了成熟过程并消除了最终产物在颗粒中的积累，这表明前肽对于前MPO的后期加工和靶向颗粒中的储存具有关键作用。
Myeloperoxidase (MPO), stored in azurophil granules of neutrophils, is critical for an optimal oxygen-dependent microbicidal activity of these cells. Pro-MPO goes through a stepwise proteolytic trimming with elimination of an amino-terminal propeptide to yield one heavy and one light polypeptide chain. The propeptide of MPO may have a role in retention and folding of the nascent protein into its tertiary structure or in targeting of pro-MPO for processing and storage in granules, A propeptide-deleted pro-MPO mutant (MPO Delta pro) was constructed to determine if deletion of the propeptide interferes with processing and targeting after transfection to the myeloid 32D cell line. Transfection of full-length cDNA for human MPO results in normal processing and targeting of MPO to cytoplasmic dense organelles. Although the efficiency of incorporation was lower for MPO Delta pro, both pro-MPO and MPO Delta pro showed heme incorporation indicating that the propeptide is not critical for this process. Deletion of the propeptide results in synthesis of a protein that lacks processing into mature two-chain forms but rather is degraded intracellularly or secreted, The finding of continued degradation of MPO Delta pro in the presence of lysosomotrophic agents or brefeldin A rules out that the observed degradation takes place after transfer to granules, Intracellular pro-MPO has high mannose oligosaccharide side chains, whereas stored mature MPO was found to have both high mannose and complex oligosaccharide side chains as judged by only partial sensitivity to endoglycosidase H. The propeptide may normally interfere with the generation of certain complex oligosaccharide chain(s) supported by the finding of high mannose side chains in secreted pro-MPO and lack of them in MPO Delta pro that contained complex oligosaccharide side chains only. In conclusion, elimination of the propeptide of pro-MPO blocks the maturation process and abolishes accumulation of the final product in granules suggesting a critical role of the propeptide for late processing of pro-MPO and targeting for storage in granules.