Tamang David L, Alves Bryce N, Elliott Viki, Redelman Doug, Wadhwa Renu, Fraser Stephanie A, Hudig Dorothy
Department of Microbiology and Immunology MS320, University of Nevada, School of Medicine, Reno, NV 89557, USA.
Cell Immunol. 2009;255(1-2):82-92. doi: 10.1016/j.cellimm.2008.12.001. Epub 2009 Jan 14.
Perforin, a membrane-permeabilizing protein, is important to T cell cytotoxic action. Perforin has potential to damage the T cell in the endoplasmic reticulum (ER), is sequestered in granules, and later is exocytosed to kill cells. In the ER and after exocytosis, calcium and pH favor perforin activity. We found a novel perforin inhibitor associated with cytotoxic T cell granules and termed it Cytotoxic Regulatory Protein 2 (CxRP2). CxRP2 blocked lysis by granule extracts, recombinant perforin and T cells. Its effects lasted for hours. CxRP2 was calcium stable and refractory to inhibitors of granzyme and cathepsin proteases. Through mass spectrometric analysis of active 50-100 kDa proteins, we identified CxRP2 candidates. Protein disulfide isomerase A3 was the strongest candidate but was unavailable for testing; however, protein disulfide isomerase A1 had CxRP2 activity. Our results indicate that protein disulfide isomerases, in the ER or elsewhere, may protect T cells from their own perforin.
穿孔素是一种可使膜通透的蛋白质，对T细胞的细胞毒性作用至关重要。穿孔素有可能在内质网（ER）中损伤T细胞，被隔离在颗粒中，随后通过胞吐作用杀死细胞。在内质网和胞吐作用后，钙和pH值有利于穿孔素发挥活性。我们发现了一种与细胞毒性T细胞颗粒相关的新型穿孔素抑制剂，并将其命名为细胞毒性调节蛋白2（CxRP2）。CxRP2可阻断颗粒提取物、重组穿孔素和T细胞引起的细胞裂解。其作用可持续数小时。CxRP2对钙稳定，对颗粒酶和组织蛋白酶蛋白酶抑制剂具有抗性。通过对活性50 - 100 kDa蛋白质的质谱分析，我们确定了CxRP2的候选蛋白。蛋白质二硫键异构酶A3是最强的候选蛋白，但无法用于测试；然而，蛋白质二硫键异构酶A1具有CxRP2活性。我们的结果表明，内质网或其他部位的蛋白质二硫键异构酶可能保护T细胞免受自身穿孔素的损伤。
