Department of Pathology, Hokkaido University Graduate School of Medicine, Sapporo, Japan,
Arch Immunol Ther Exp (Warsz). 2013 Oct;61(5):357-65. doi: 10.1007/s00005-013-0234-1. Epub 2013 May 7.
The thymoproteasome is a specialized type of proteasomes expressed exclusively in the thymic cortex. It has a unique catalytic subunit β5t with unusual enzymatic activity. The thymoproteasome exhibits lower chymotrypsin-like activity than other forms of proteasomes such as constitutive proteasomes and immunoproteasomes. Its cleavage specificity appears uniquely suited for the production of peptides that mediate positive selection of CD8⁺ T cells. Similar to major histocompatibility complex molecules and T/B-cell receptors, the thymoproteasome occurs only in jawed vertebrates, suggesting that it evolved concomitant with the cardinal elements of adaptive immunity. β5t can be used as a marker in the differential diagnosis of thymic tumors. It is expressed in most type B and some type AB thymomas, but not in type A thymoma, thymic carcinoma, or tumors of non-thymic epithelial origin.
胸腺蛋白酶体是一种专门的蛋白酶体，仅在胸腺皮质中表达。它具有独特的催化亚基β5t，具有异常的酶活性。胸腺蛋白酶体的糜蛋白酶样活性低于其他形式的蛋白酶体，如组成型蛋白酶体和免疫蛋白酶体。其切割特异性似乎特别适合产生介导 CD8⁺T 细胞阳性选择的肽。与主要组织相容性复合物分子和 T/B 细胞受体一样，胸腺蛋白酶体仅存在于有颌脊椎动物中，表明它与适应性免疫的关键要素同时进化。β5t 可作为胸腺瘤鉴别诊断的标志物。它在大多数 B 型和一些 AB 型胸腺瘤中表达，但在 A 型胸腺瘤、胸腺癌或非胸腺上皮来源的肿瘤中不表达。
