Interferon gamma stimulation modulates the proteolytic activity and cleavage site preference of 20S mouse proteasomes.
Interferon gamma stimulation modulates the proteolytic activity and cleavage site preference of 20S mouse proteasomes.
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DOI：
10.1084/jem.179.3.901
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发表时间：
1994-03-01
期刊：
影响因子：
--
通讯作者：
Kloetzel PM
中科院分区：
文献类型：
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作者：
Boes B;Hengel H;Ruppert T;Multhaup G;Koszinowski UH;Kloetzel PM
蛋白酶体是一个700 kD的多亚基酶复合物，具有几个蛋白水解活性位点。该酶复合物参与泛素依赖性和非依赖性蛋白质降解，并可能有助于处理由主要组织相容性复合物（MHC）I类分子呈递的抗原。在这里，我们证明，治疗小鼠成纤维细胞与20 U干扰素γ（IFN-γ）3天诱导蛋白酶体亚基组成的变化，β-型亚基LMP 2，这是在MHC II类区域编码，被纳入酶复合物。这是通过同源δ亚基的减少来实现的。IFN-γ刺激导致20 S蛋白酶体的胰凝乳蛋白酶样Suc-LLVY-MCA肽水解活性下调，而胰蛋白酶样活性保持不受影响。当将合成的25-mer多肽作为底物进行测试时，其序列覆盖MCMV pp 89的抗原性九肽YPHFMPTNL，IFN-γ诱导的细胞的20 S蛋白酶体表现出改变的胰凝乳蛋白酶样切割位点偏好。在没有IFN-γ诱导的情况下，由MHC I类分子呈递的天然加工的九聚体肽表现为次要的切割产物。IFN-γ活化不会导致最终肽的增加，但会产生一组不同的肽。我们假设，这些肽代表前体肽，可以修剪到最终的肽大小。
The proteasome is a 700-kD multisubunit enzyme complex with several proteolytically active sites. The enzyme complex is involved in both ubiquitin-dependent and -independent protein degradation and may contribute to the processing of antigens presented by major histocompatibility complex (MHC) class I molecules. Here we demonstrate that treatment of mouse fibroblast cells with 20 U interferon gamma (IFN-gamma) for 3 d induces a change in the proteasome subunit composition and that the beta-type subunit LMP2, which is encoded in the MHC class II region, is incorporated into the enzyme complex. This is paralleled by reduction of the homologous delta-subunit. IFN-gamma stimulation results in a downregulation of the chymotrypsin-like Suc- LLVY-MCA peptide hydrolyzing activity of 20S proteasomes whereas the trypsin-like activity remains unaffected. When tested as a substrate a synthetic 25-mer polypeptide whose sequence covers the antigenic nonapeptide YPHFMPTNL of the MCMV pp89, 20S proteasomes of IFN-gamma- induced cells exhibit altered chymotrypsin-like cleavage site preferences. In the absence of IFN-gamma induction, the naturally processed nonamer peptide that is presented by MHC class I molecules appears as a minor cleavage product. IFN-gamma activation does not result in an increase of the final peptide but results in a different set of peptides. We hypothesize that these peptides represent precursor peptides that can be trimmed to final peptide size.