Natural processing sites for human cathepsin E and cathepsin D in tetanus toxin: implications for T cell epitope generation.
Natural processing sites for human cathepsin E and cathepsin D in tetanus toxin: implications for T cell epitope generation.
复制标题
破伤风毒素中人组织蛋白酶 E 和组织蛋白酶 D 的自然加工位点：对 T 细胞表位生成的影响。
作者：
E. Hewitt;A. Treumann;N. Morrice;P. Tatnell;J. Kay;C. Watts
组织蛋白酶E是一种天冬氨酸氨基转移酶，在抗原加工过程中经常出现在II类MHC分子上，但目前还没有关于其在AGS内与已知T细胞表位相关的切割特异性的信息。我们分析了组织蛋白酶E对破伤风毒素的一个大的C末端结构域(残基872-1315)的加工，并将加工产物与组织蛋白酶D释放的产物进行了比较，组织蛋白酶D是一种相关的天冬氨酸蛋白酶，也被认为参与了II类MHC限制性抗原的加工。利用反相高效液相色谱分离多肽，对加工产物进行N-末端Edman降解和质谱分析。共鉴定了28个切割位点，其中11个被组织蛋白E和D识别。大多数(尽管不是全部)位于两对疏水残基之间，位于已知含有几个人类T细胞表位的200个氨基酸的C末端区域。以前描述的T细胞表位，例如，在残基1273和1284之间，侧翼有组织蛋白酶E和D裂解位点。这些数据与组织蛋白E和/或D在人类免疫系统的抗原加工中的重要作用是一致的。
Cathepsin E is an aspartic proteinase that has been implicated frequently in Ag processing for presentation on class II MHC molecules, but no information exists on its cleavage specificity within Ags in relation to known T cell epitopes. We have analyzed the processing by cathepsin E of a large C-terminal domain of tetanus toxin (residues 872-1315), and we have compared the processing products with those liberated by cathepsin D, a related aspartic proteinase also thought to be involved in class II MHC-restricted Ag processing. Processing products were analyzed by N-terminal Edman degradation and mass spectrometry following reverse-phase HPLC separation of peptides. A total of 28 cleavage sites was identified, 11 of which were recognized by both cathepsins E and D. Most, although not all, sites were between pairs of hydrophobic residues and were located within the 200-amino-acid C terminal region known to contain several human T cell epitopes. Previously described T cell epitopes, for example, between residues 1273 and 1284, were flanked by cathepsin E and D cleavage sites. These data are consistent with an important role for cathepsins E and/or D in Ag processing in the human immune system.