Commentary to: "Post-translational processing of hepcidin in human hepatocytes is mediated by the prohormone convertase furin," by Erika Valore and Tomas Ganz.
Commentary to: "Post-translational processing of hepcidin in human hepatocytes is mediated by the prohormone convertase furin," by Erika Valore and Tomas Ganz.
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对“人类肝细胞中铁调素的翻译后加工是由激素原转化酶弗林蛋白酶介导”的评论，作者：Erika Valore 和 Tomas Ganz。
DOI：
10.1016/j.bcmd.2007.07.010
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Lee,Pauline
中科院分区：
文献类型：
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作者：
Lee,Pauline
由于铁调素在调节铁稳态中的中心作用，该肽的翻译后加工具有潜在的重要性，但迄今为止很少受到关注。因此，我们发现Valore和Ganz报道的结果表明，弗林蛋白酶前体蛋白转化酶的抑制剂影响在弗林蛋白酶共有序列RXRR处将原铁调素加工成成熟铁调素。我们还从两个角度探讨了这一过程。首先，我们已经详细研究了这种切割的序列要求，特别是基于已知的人类突变。第二，我们提出了铁调素产生的调控不仅发生在转录水平上的可能性，这一点已经在几个实验室中得到了广泛的研究，而且还发生在翻译后水平上，这一点几乎完全被忽视。值得注意的是，Jacolot et al [1]报道的铁调素中存在先前描述的突变，R59 G，即弗林蛋白酶切割共有序列P1位点的预测精氨酸。由于突变留下4个完整的弗林蛋白酶，可以预测弗林蛋白酶仍然能够切割R59 G突变体铁调素，只要P1'位点的甘氨酸是可接受的。我们已经制备了几种铁调素原的突变体，以检查铁调素原向成熟铁调素的加工（图1）。我们的研究表明，R59 G突变（QRRRR↓ GDTHF）不能有效切割，但D 60 G突变（QRRRR ↓ GTHF）可以有效切割。这表明在P1'位点存在一个甘氨酸是可以接受的，但可能存在四个甘氨酸是不够的。事实上，我们发现铁调素双突变体R58 G/R59 G的切割只留下共有序列的三个碱基（QRRR↓ GGDTHF），与具有四个碱基的R59 G突变体没有区别。我们进一步研究了P1 '、P2'、P4'和P4'位点的重要性。具有识别序列RRRRR↓ FPIC的缺失的氨基酸60-62（22聚体）和缺失的60-64（20聚体）（RRRRR↓ ICIF）的原肝素酶突变体分别被低效加工和完全不加工。T61 I（RRRRR↓ DIHF）和H62 W（RRRRR↓ DTWF）铁调素原突变体的裂解产物与F63 F（RRRRR↓ DTHY）铁调素原突变体不同，后者更大。T61 I（P2 '）和H62 W（P3'）突变体的迁移表明它们被加工成20-和22聚体形式，因为它们与22聚体切割产物共迁移，但F63 Y（P4 '）突变体被切割成更大形式（可能是25聚体）的铁调素，其对进一步加工成铁调素具有抗性。
Because of the central role of hepcidin in the regulation of iron homeostasis, the posttranslational processing of the peptide is of potential importance, but has heretofore received scant attention. We therefore find the results reported by Valore and Ganz demonstrating that inhibitors of furin proprotein convertases affect processing of prohepcidin to mature hepcidin at the furin consensus sequence RXRR of special interest. We have also explored this process from two points of view. First of all, we have studied the sequence requirements for this cleavage in some detail, particularly based upon a known human mutation. Secondly, we have addressed the possibility that regulation of hepcidin production occurs not only at the transcriptional level, which has been studied extensively in several laboratories, but also at the posttranslational level, which has been almost entirely neglected.The sequence surrounding the human hepcidin cleavage site is QRRRRR↓ DTHF and the mouse hepcidin cleavage site is QKRRKR↓ DTNF. It is notable that there is a previously described mutation in hepcidin reported by Jacolot et al [1], R59G, the predicted arginine in the P1 site of the furin cleavage consensus sequence. Since the mutation leaves 4 intact arginines, one would predict that furin would still be able to cleave R59G mutant hepcidin provided the glycine in the P1’site is acceptable. We have made several mutants of prohepcidin in order to examine processing of prohepcidin to mature hepcidin (Figure 1). Our studies have shown that the R59G mutation (QRRRR↓ GDTHF) is not cleaved efficiently but a D60G mutation (QRRRRR↓ GTHF) is cleaved efficiently. This suggests that the presence of a glycine in the P1’site is acceptable but, possibly, the presence of four arginines is not sufficient. In fact, we found that cleavage of a hepcidin double mutant R58G/R59G that would leave only three arginines of the consensus sequence (QRRR↓ GGDTHF) was indistinguishable from the R59G mutant with four arginines. We further examined the importance of the P1’, P2’, P4’and P4’sites. The prohepcicin mutants with deleted amino acids 60–62 (22mer) with the recognition sequence RRRRR↓ FPIC and deleted 60–64 (20mer)(RRRRR↓ ICIF) were inefficiently processed and not processed at all, respectively. The T61I (RRRRR↓ DIHF) and the H62W (RRRRR↓ DTWF) prohepcidin mutants cleavage products were different from the F63F (RRRRR↓ DTHY) prohepcidin mutant, the latter being larger. The migration of the T61I (P2’) and H62W (P3’) mutants suggested that they were processed to the 20-and 22 mer forms since they comigrated with the 22mer cleavage products but the F63Y (P4’) mutant was cleaved to a larger form (possibly 25mer) of hepcidin that was resistant to further processing to the