Major histocompatibility complex class I-presented antigenic peptides are degraded in cytosolic extracts primarily by thimet oligopeptidase
Major histocompatibility complex class I-presented antigenic peptides are degraded in cytosolic extracts primarily by thimet oligopeptidase
复制标题
DOI：
10.1074/jbc.m105517200
复制
发表时间：
2001-09-28
影响因子：
4.8
通讯作者：
Goldberg, AL
中科院分区：
文献类型：
--
作者：
Saric, T;Beninga, J;Goldberg, AL
几乎所有由蛋白酶体在蛋白质降解过程中产生的肽都会快速消化为氨基酸，但少数蛋白酶体产物逃脱了这种命运，并在细胞表面主要组织相容性复合物 I 类分子上呈递给免疫系统。为了测试这些抗原肽是否可能对胞质肽酶具有固有的抗性，将六种不同的抗原肽与 HeLa 细胞提取物一起孵育。所有六种物质都通过邻菲咯啉敏感金属肽酶的过程迅速降解。提取物中的一种抗原肽 FAPGNYPAL 被贝斯汀敏感的外肽酶（显然是嘌呤霉素敏感的氨肽酶）迅速破坏。胞浆内肽酶的特异性抑制剂、蒂美特寡肽酶 (TOP) (EC 3.4.24.15) 可将其他五种酶的消失减少 30-90%，但其生理功能尚不清楚且存在争议。所有这些肽都对纯重组 TOP 敏感。此外，在分离提取物时，降解卵清蛋白衍生表位的主要肽酶峰 SIINFEKL 与 TOP 共同纯化。在提取物中，TOP 还催化 SIINFEKL 的 N 延伸变体和其他抗原肽的快速降解，这些抗原肽在体内可以作为这些主要组织相容性复合物呈递的表位的前体。这种酶（与促进抗原肽产生的细胞蛋白不同）不受干扰素-γ 的调节。 TOP 似乎主要负责细胞质提取物中抗原肽的快速分解，我们的相关研究（A. X. Y. Mo、K. Lemerise、W. Zeng、Y. Shen、C. R. Abraham、A. L. Goldberg 和 K. L. Rock，已提交发表）表明 TOP 通过破坏此类肽来限制体内抗原呈递。
Nearly all peptides generated by proteasomes during protein degradation are digested rapidly to amino acids, but a few proteasomal products escape this fate and are presented to the immune system on cell surface major histocompatibility complex class I molecules. To test whether these antigenic peptides may be inherently resistant to cytosolic peptidases, six different antigenic peptides were incubated with HeLa cell extracts. All six were degraded rapidly by a process involving o-phenanthroline-sensitive metallopeptidases. One antigenic peptide, FAPGNYPAL, was rapidly destroyed in the extracts by a bestatin-sensitive exopeptidase, apparently by the puromycin-sensitive aminopeptidase. The disappearance of the other five was reduced 30-90% by a specific inhibitor of the cytosolic endopeptidase, thimet oligopeptidase (TOP) (EC 3.4.24.15), whose physiological function(s) have been unclear and controversial. All these peptides were sensitive to pure recombinant TOP. Furthermore, upon fractionation of the extracts, the major peptidase peak that degraded the ovalbumin-derived epitope, SIINFEKL, co-purified with TOP. In the extracts, TOP also catalyzed rapid degradation of N-extended variants of SIINFEKL and of other antigenic peptides, which in vivo can serve as precursors of these major histocompatibility complex-presented epitopes. This enzyme (unlike cell proteins that promote production of antigenic peptides) is not regulated by interferon-gamma. TOP seems to be primarily responsible for the rapid breakdown of antigenic peptides in cytosolic extracts, and our related studies (A. X. Y. Mo, K. Lemerise, W. Zeng, Y. Shen, C. R. Abraham, A. L. Goldberg, and K. L. Rock, submitted for publication) indicate that TOP by destroying such peptides limits antigen presentation in vivo.