Abstract：
Metacaspases are cysteine proteases present in plants, fungi and protists. While the association of metacaspases with cell death is studied in a range of organisms, their native substrates are largely unknown. Here, we explored the in vivo proteolytic landscape of the two metacaspases, CrMCA-I and CrMCA-II, present in the green freshwater alga Chlamydomonas reinhardtii, using mass spectrometry-based degradomics approach, during control conditions and salt stress. Comparison between the cleavage events of CrMCA-I and CrMCA-II in metacaspase mutants revealed unique cleavage preferences and substrate specificity. Degradome analysis demonstrated the relevance of the predicted metacaspase substrates to the physiology of C. reinhardtii cells and its adaptation during salt stress. Functional enrichment analysis indicated an involvement of CrMCA-I in the catabolism of carboxylic acids, while CrMCA-II plays an important role in photosynthesis and translation. Altogether, our findings suggest distinct cellular functions of the two metacaspases in C. reinhardtii during salt stress response.
摘要：
Metacaspases是存在于植物中的半胱氨酸蛋白酶,真菌和原生生物。虽然在一系列生物体中研究了β-半胱天冬酶与细胞死亡的关联，它们的天然底物在很大程度上是未知的。这里,我们探索了两种谷冬酶的体内蛋白水解景观，CrMCA-I和CrMCA-II,存在于绿色淡水藻类莱茵衣藻中，使用基于质谱的降解组学方法，在控制条件和盐胁迫期间。在超半胱氨酸蛋白酶突变体中CrMCA-I和CrMCA-II的裂解事件之间的比较揭示了独特的裂解偏好和底物特异性。降解体分析证明了预测的β-半胱天冬酶底物与莱茵衣原体细胞的生理学及其在盐胁迫期间的适应性的相关性。功能富集分析表明CrMCA-I参与羧酸的分解代谢，而CrMCA-II在光合作用和翻译中起着重要作用。总之,我们的发现表明，在盐应激反应过程中，莱茵衣原体中的两种β-胱天蛋白酶具有不同的细胞功能。
