Autoactivation of Mouse Trypsinogens Is Regulated by Chymotrypsin C via Cleavage of the Autolysis Loop
Autoactivation of Mouse Trypsinogens Is Regulated by Chymotrypsin C via Cleavage of the Autolysis Loop
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DOI：
10.1074/jbc.m113.478800
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发表时间：
2013-08-16
影响因子：
4.8
通讯作者：
Sahin-Toth, Miklos
中科院分区：
文献类型：
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作者：
Nemeth, Balazs Csaba;Wartmann, Thomas;Sahin-Toth, Miklos
胰凝乳蛋白酶C（CTRC）是人体胰蛋白酶原自激活的蛋白水解调节因子。胰蛋白酶原活化肽的CTRC裂解刺激自活化，而钙结合环的裂解促进胰蛋白酶原降解。胰蛋白酶原突变改变了这些调节裂解，导致胰腺内胰蛋白酶原激活增加，并引起遗传性胰腺炎。本研究的目的是表征小鼠Ctrc对小鼠胰蛋白酶原自激活的调节。我们发现小鼠胰腺表达四种高水平的胰蛋白酶原亚型，T7，T8，T9和T20。只有T7激活肽被小鼠Ctrc切割，导致可忽略的自激活刺激。令人惊讶的是，小鼠Ctrc在所有小鼠胰蛋白酶原中切割钙结合环较差。相比之下，小鼠Ctrc容易切割T8和T9的自溶环中的Phe-150-Gly-151肽键并抑制自活化。小鼠胰凝乳蛋白酶B也裂解相同的肽键，但慢7倍。T7对胰凝乳蛋白酶调节不太敏感，胰凝乳蛋白酶调节涉及自溶环中Leu-149-Ser-150肽键的缓慢裂解。建模表明空间接近的自溶环和胰蛋白酶原中的激活肽，这表明裂解的自溶环可能直接干扰激活。我们的结论是，自激活的小鼠胰蛋白酶原的控制下，小鼠Ctrc与一些显着的差异，从人类的情况。因此，胰蛋白酶原活化肽或钙结合环被Ctrc切割是不重要的。相反，通过裂解自溶环抑制自激活是可以减轻胰腺内胰蛋白酶原激活的主要机制。
Chymotrypsin C (CTRC) is a proteolytic regulator of trypsinogen autoactivation in humans. CTRC cleavage of the trypsinogen activation peptide stimulates autoactivation, whereas cleavage of the calcium binding loop promotes trypsinogen degradation. Trypsinogen mutations that alter these regulatory cleavages lead to increased intrapancreatic trypsinogen activation and cause hereditary pancreatitis. The aim of this study was to characterize the regulation of autoactivation of mouse trypsinogens by mouse Ctrc. We found that the mouse pancreas expresses four trypsinogen isoforms to high levels, T7, T8, T9, and T20. Only the T7 activation peptide was cleaved by mouse Ctrc, causing negligible stimulation of autoactivation. Surprisingly, mouse Ctrc poorly cleaved the calcium binding loop in all mouse trypsinogens. In contrast, mouse Ctrc readily cleaved the Phe-150-Gly-151 peptide bond in the autolysis loop of T8 and T9 and inhibited autoactivation. Mouse chymotrypsin B also cleaved the same peptide bond but was 7-fold slower. T7 was less sensitive to chymotryptic regulation, which involved slow cleavage of the Leu-149-Ser-150 peptide bond in the autolysis loop. Modeling indicated steric proximity of the autolysis loop and the activation peptide in trypsinogen, suggesting the cleaved autolysis loop may directly interfere with activation. We conclude that autoactivation of mouse trypsinogens is under the control of mouse Ctrc with some notable differences from the human situation. Thus, cleavage of the trypsinogen activation peptide or the calcium binding loop by Ctrc is unimportant. Instead, inhibition of autoactivation via cleavage of the autolysis loop is the dominant mechanism that can mitigate intrapancreatic trypsinogen activation.