Incomplete processing of proinsulin to insulin accompanied by elevation of des-31,32 proinsulin intermediates in islets of mice lacking active PC2
Incomplete processing of proinsulin to insulin accompanied by elevation of des-31,32 proinsulin intermediates in islets of mice lacking active PC2
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DOI：
10.1074/jbc.273.6.3431
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发表时间：
1998-02-06
影响因子：
4.8
通讯作者：
Steiner, DF
中科院分区：
文献类型：
--
作者：
Furuta, M;Carroll, R;Steiner, DF
激素原转化酶 PC2 (SPC2) 和 PC3/PC1 (SPC3) 是多种神经和内分泌组织中主要的前体加工内切蛋白酶。这两种酶通常在胰岛β细胞中表达并参与胰岛素原加工。最近，我们生成了由于 PC2 基因破坏而缺乏活性 PC2 的小鼠（Furuta, M.、Yano, H.、Zhou, A.、Rouille, Y.、Hoist, J. J.、Carroll, R. J.、Ravazzola, M.、Orci, L.、Furuta, H. 和 Steiner, D. F. (1997) Proc. Natl. Acad. Sci. U.S. A. 94， 6646-6651）。在这里，我们报告这些 PC2 突变小鼠的循环胰岛素原升高，其中包含 60% 的免疫反应性胰岛素样成分。从胰腺中酸乙醇提取的胰岛素原也显着升高，约占总免疫反应性胰岛素样成分的 35%。这些增加的胰岛素原主要储存在分泌颗粒中，导致电子显微镜下的外观发生改变。在脉冲追踪实验中，突变胰岛将比正常胰岛更少的同位素氨基酸掺入胰岛素相关成分中。在野生型和突变型胰岛中，胰岛素原 I 被更快地加工成胰岛素，这反映了 PC2 和 PC3 对具有位于裂解位点上游四个残基的碱性氨基酸的底物的偏好。在突变胰岛中，胰岛素原转化为胰岛素的总半衰期增加了约 3 倍，并且与 des-31,32 胰岛素原升高 4-5 倍相关，des-31,32 胰岛素原是一种中间体，由 PC3 在 B 链-C 肽连接处优先裂解胰岛素原形成，并在 C 末端被羧肽酶 E 加工以去除 Arg(31) 和 Arg(32)。在追踪的前 1-2 小时内，突变型和野生型胰岛新合成的胰岛素原的持续释放是正常的（
The prohormone convertases PC2 (SPC2) and PC3/PC1 (SPC3) are the major precursor processing endoproteases in a wide variety of neural and endocrine tissues. Both enzymes are normally expressed in the islet beta cells and participate in proinsulin processing. Recently we generated mice lacking active PC2 due to a disruption of the PC2 gene (Furuta, M., Yano, H., Zhou, A., Rouille, Y., Hoist, J. J., Carroll, R. J., Ravazzola, M., Orci, L., Furuta, H., and Steiner, D. F. (1997) Proc. Natl. Acad. Sci. U.S. A. 94, 6646-6651). Here we report that these PC2 mutant mice have elevated circulating proinsulin, comprising 60% of immunoreactive insulin-like components. Acid ethanol extractable proinsulin from pancreas is also significantly elevated, representing about 35% of total immunoreactive insulin-like components. These increased amounts of proinsulin are mainly stored in secretory granules, giving rise to an altered appearance on electron microscopy. In pulse-chase experiments, the mutant islets incorporate lesser amounts of isotopic amino acids into insulin-related components than normal islets. In both wild-type and mutant islets, proinsulin I was processed more rapidly to insulin, reflecting the preference of both PC2 and PC3 for substrates having a basic amino acid positioned four residues upstream of the cleavage site. The overall half-time for the conversion of proinsulin to insulin is increased approximately 3-fold in the mutant islets and is associated with a 4-5-fold greater elevation of des-31,32 proinsulin, an intermediate that is formed by the preferential cleavage of proinsulin at the B chain-C-peptide junction by PC3 and is C-terminally processed to remove Arg(31) and Arg(32) by carboxypeptidase E. The constitutive release of newly synthesized proinsulin from both mutant and wild-type islets during the first 1-2 h of chase was normal (