The Efficiency of Human Cytomegalovirus pp65495–503 CD8+ T Cell Epitope Generation Is Determined by the Balanced Activities of Cytosolic and Endoplasmic Reticulum-Resident Peptidases
The Efficiency of Human Cytomegalovirus pp65495–503 CD8+ T Cell Epitope Generation Is Determined by the Balanced Activities of Cytosolic and Endoplasmic Reticulum-Resident Peptidases
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DOI：
10.4049/jimmunol.1101886
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发表时间：
2012-07
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通讯作者：
S. Urban;K. Textoris-Taube;B. Reimann;K. Janek;Tanja Dannenberg;F. Ebstein;Christin Seifert;F. Zhao;J. Kessler;A. Halenius;P. Henklein;J. Paschke;S. Cadel;H. Bernhard;F. Ossendorp;T. Foulon;D. Schadendorf;A. Paschen;U. Seifert
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作者：
S. Urban;K. Textoris-Taube;B. Reimann;K. Janek;Tanja Dannenberg;F. Ebstein;Christin Seifert;F. Zhao;J. Kessler;A. Halenius;P. Henklein;J. Paschke;S. Cadel;H. Bernhard;F. Ossendorp;T. Foulon;D. Schadendorf;A. Paschen;U. Seifert
人CMV（HCMV）感染的控制取决于CD 8 + CTL的细胞毒性活性。在HLA-A*0201感染的个体中，HCMV磷蛋白（pp）65是主要的CTL靶抗原，pp 65495 -503是免疫显性CTL表位。由于免疫显性由特定表位的表面丰度强烈决定，因此我们要求确定pp 65495 -503生成效力的细胞Ag加工机制的组分，特别是蛋白酶体、胞质肽酶和内质网（ER）驻留肽酶。体外Ag处理实验表明，标准蛋白酶体和免疫蛋白酶体产生最小的9-mer肽表位以及不同长度的N-末端延长的表位前体。这些肽在很大程度上被胞质肽酶亮氨酸氨肽酶和三肽基肽酶II降解，如亮氨酸氨肽酶和三肽基肽酶II敲低后pp 65495 -503表位呈递增加所证明的。此外，利用脯氨酰寡肽酶和氨肽酶B，我们鉴定了两种新的Ag加工机制组分，其通过破坏pp 65495 -503表位限制了特异性肽库的可用性。与胞质肽酶相反，ER氨基肽酶1和2的沉默强烈损害pp 65495 -503特异性T细胞活化，表明ER氨基肽酶在pp 65495 -503生成中的重要性。因此，胞质肽酶主要干扰pp 65495 -503表位的产生，而ER-驻留氨基肽酶增强这种产生。因此，我们的实验表明，胞质和ER驻留肽酶活性的组合强烈地塑造了特异性抗原肽的库，从而调节MHC I类表位呈递效率。
Control of human CMV (HCMV) infection depends on the cytotoxic activity of CD8+ CTLs. The HCMV phosphoprotein (pp)65 is a major CTL target Ag and pp65495–503 is an immunodominant CTL epitope in infected HLA-A*0201 individuals. As immunodominance is strongly determined by the surface abundance of the specific epitope, we asked for the components of the cellular Ag processing machinery determining the efficacy of pp65495–503 generation, in particular, for the proteasome, cytosolic peptidases, and endoplasmic reticulum (ER)-resident peptidases. In vitro Ag processing experiments revealed that standard proteasomes and immunoproteasomes generate the minimal 9-mer peptide epitope as well as N-terminal elongated epitope precursors of different lengths. These peptides are largely degraded by the cytosolic peptidases leucine aminopeptidase and tripeptidyl peptidase II, as evidenced by increased pp65495–503 epitope presentation after leucine aminopeptidase and tripeptidyl peptidase II knockdown. Additionally, with prolyl oligopeptidase and aminopeptidase B we identified two new Ag processing machinery components, which by destroying the pp65495–503 epitope limit the availability of the specific peptide pool. In contrast to cytosolic peptidases, silencing of ER aminopeptidases 1 and 2 strongly impaired pp65495–503-specific T cell activation, indicating the importance of ER aminopeptidases in pp65495–503 generation. Thus, cytosolic peptidases primarily interfere with the generation of the pp65495–503 epitope, whereas ER-resident aminopeptidases enhance such generation. As a consequence, our experiments reveal that the combination of cytosolic and ER-resident peptidase activities strongly shape the pool of specific antigenic peptides and thus modulate MHC class I epitope presentation efficiency.