Internalization of exogenous cystatin F supresses cysteine proteases and induces the accumulation of single-chain cathepsin L by multiple mechanisms.
Internalization of exogenous cystatin F supresses cysteine proteases and induces the accumulation of single-chain cathepsin L by multiple mechanisms.
复制标题
DOI：
10.1074/jbc.m111.253914
复制
发表时间：
2011-12-09
期刊：
影响因子：
--
通讯作者：
Watts C
中科院分区：
文献类型：
--
作者：
Colbert JD;Matthews SP;Kos J;Watts C
背景：半胱氨酸氨基转移酶F是一种蛋白水解酶抑制物，通常存在于内吞途径中，但可以分泌。结果：分泌的半胱氨酸氨基转移酶F可被内化，从而抑制多个靶点，引起组织蛋白酶L的积聚。结论：半胱氨酸氨基转移酶F抑制CATL转换酶AEP，稳定CATL蛋白水平。意义：分泌型半胱氨酸氨基转移酶F可被激活，反式扩展其抑制潜能，使其超出其合成部位。半胱氨酸氨基转移酶F是半胱氨酸氨基转移酶抑制剂家族中的一个特殊成员，它是一种非活性二聚体，在产生它的免疫细胞的内切/溶酶体途径中被蛋白分解激活。然而，有一部分是分泌的，可以被其他细胞摄取和激活。我们在这里显示，以这种方式获得的胱抑素F诱导组织蛋白L(CATL)的单链形式的戏剧性积累。共沉淀研究表明，胱抑素F与CATL在相同的细胞隔室中观察到，并且与CATL紧密结合。观察到的单链CATL的积累部分是由于cystatin F介导的可能的单链到双链CATL转换酶AEP/Legumain的抑制，部分是由于组织蛋白酶活性的普遍抑制。因此，胱抑素F稳定CATL，导致由单链或双链形式组成的非活性复合体的戏剧性积累，这取决于胱抑素F抑制AEP的能力。因此，将胱抑素F从一个细胞交叉转移到另一个细胞可能会减弱CATL活性过高的潜在有害影响，而矛盾的是，它会导致CATL蛋白的积累。最后，我们确认了之前的数据(Beers，C.，Honey，K.，Fink，S.，ForBush，K.和Rudensky，A.(2003)J.Exp.地中海医院。197,169-179)，显示在干扰素γ激活的巨噬细胞中，CATL活性丧失，但CATL蛋白没有丢失。然而，我们在野生型和cystatin F缺失的巨噬细胞中发现了CATL活性的同等损失，这表明除了cystatin F之外的一种抑制活性可以抑制激活的巨噬细胞中的CATL活性。
Background: Cystatin F is a protease inhibitor normally found within the endocytic pathway, but can be secreted. Results: Secreted cystatin F can be internalized thereby inhibiting multiple targets and causing the accumulation of cathepsin L. Conclusion: Cystatin F inhibits the CatL convertase AEP and stabilizes CatL protein levels. Significance: Secreted cystatin F can be activated in trans expanding its inhibitory potential beyond its site of synthesis. Cystatin F is an unusual member of the cystatin family of protease inhibitors, which is made as an inactive dimer and becomes activated by proteolysis in the endo/lysosome pathway of the immune cells that produce it. However a proportion is secreted and can be taken up and activated by other cells. We show here that cystatin F acquired in this way induces a dramatic accumulation of the single-chain form of cathepsin L (CatL). Cystatin F was observed in the same cellular compartments as CatL and was tightly complexed with CatL as determined by co-precipitation studies. The observed accumulation of single-chain CatL was partly due to cystatin F-mediated inhibition of the putative single-chain to two-chain CatL convertase AEP/legumain and partly to general suppression of cathepsin activity. Thus, cystatin F stabilizes CatL leading to the dramatic accumulation of an inactive complex composed either of the single-chain or two-chain form depending on the capacity of cystatin F to inhibit AEP. Cross-transfer of cystatin F from one cell to another may therefore attenuate potentially harmful effects of excessive CatL activity while paradoxically, inducing accumulation of CatL protein. Finally, we confirmed earlier data (Beers, C., Honey, K., Fink, S., Forbush, K., and Rudensky, A. (2003) J. Exp. Med. 197, 169–179) showing a loss of CatL activity, but not of CatL protein, in macrophages activated with IFNγ. However, we found equivalent loss of CatL activity in wild type and cystatin F-null macrophages suggesting that an inhibitory activity other than cystatin F quenches CatL activity in activated macrophages.