Proconvertase proteolytic processing of an enzymatically active myeloperoxidase precursor
Proconvertase proteolytic processing of an enzymatically active myeloperoxidase precursor
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DOI：
10.1016/j.abb.2012.07.013
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发表时间：
2012-11-01
影响因子：
3.9
通讯作者：
Nauseef, William M.
中科院分区：
文献类型：
--
作者：
McCormick, Sally;Nelson, Angela;Nauseef, William M.
人嗜中性粒细胞对摄入的微生物的最佳和有效的杀灭在很大程度上是由吞噬体中的髓过氧化物酶-H2 O2-氯化物系统产生的次氯酸的作用介导的。髓过氧化物酶基因转录仅限于骨髓中的早期髓样前体，此时髓过氧化物酶被合成并储存在嗜天青颗粒中，随后从刺激的中性粒细胞释放。前髓过氧化物酶是在内质网（ER）中合成的90 kDa髓过氧化物酶前体，含有125个氨基酸的前区，其在髓过氧化物酶生物合成过程中的功能和命运尚不清楚。在髓过氧化物酶生物合成过程中，前髓过氧化物酶具有两种命运;大多数经历蛋白水解加工以产生成熟的髓过氧化物酶，而其余部分从骨髓中的细胞组成性分泌。我们使用的早幼粒细胞细胞系，产生内源性髓过氧化物酶，以及稳定表达正常和突变形式的髓过氧化物酶的人胚肾细胞检查蛋白水解加工的早幼粒过氧化物酶。我们证明，CMK-RVKR，枯草杆菌蛋白酶样蛋白酶的抑制剂，阻断切割的前髓过氧化物酶的前肽在后ER室。突变体丙氨酸取代预测的蛋白酶裂解位点的碱性残基未能经历成熟正常髓过氧化物酶亚基，并在前髓过氧化物酶阶段被捕。而具体的突变体变化，以他们的稳定性，分泌的原髓过氧化物酶的突变体保留的能力，产生次氯酸。总之，这些研究表明，前髓过氧化物酶的前转化酶依赖性裂解作为髓过氧化物酶的正常蛋白水解加工和颗粒靶向的重要步骤。此外，虽然蛋白酶切割位点的突变降低了突变体的细胞内稳定性，但血红素基团的完整性并未受到损害，因为氯化活性保留在分泌的前髓过氧化物酶中。爱思唯尔公司出版
Optimal and efficient killing of ingested microbes by human neutrophils is mediated in large part by the action of hypochlorous acid produced by the myeloperoxidase-H2O2-chloride system in phagosomes. Myeloperoxidase gene transcription is limited to early myeloid precursors in the bone marrow, when myeloperoxidase is synthesized and stored in azurophilic granules for subsequent release from stimulated neutrophils. Promyeloperoxidase, the 90 kDa myeloperoxidase precursor synthesized in the endoplasmic reticulum (ER), contains a 125-amino acid pro-region whose function and fate during myeloperoxidase biosynthesis are unknown. Promyeloperoxidase has two fates during myeloperoxidase biosynthesis; the majority undergoes proteolytic processing to generate mature myeloperoxidase, while the remainder is constitutively secreted from the cells in bone marrow. We used a promyelocytic cell line that produces endogenous myeloperoxidase as well as human embryonic kidney cells stably expressing normal and mutant forms of myeloperoxidase to examine proteolytic processing of promyeloperoxidase. We demonstrated that CMK-RVKR, an inhibitor of subtilisin-like proteinases, blocked cleavage of the propeptide of promyeloperoxidase in a post-ER compartment. Mutants with alanine substitution of basic residues in the predicted proteinase cleavage site failed to undergo maturation to normal myeloperoxidase subunits and were arrested at the promyeloperoxidase stage. Whereas specific mutants varied as to their stability, secreted promyeloperoxidase from the mutants retained the capacity to generate hypochlorous acid. Taken together, these studies demonstrate proconvertase-dependent cleavage of promyeloperoxidase as an essential step in normal proteolytic processing and granule targeting of myeloperoxidase. Furthermore, although mutations in the proteinase cleavage site reduced intracellular stability of the mutants, the integrity of the heme group was not compromised, as chlorinating activity was retained in the secreted promyeloperoxidase. Published by Elsevier Inc.