Department of Chemistry, Umeå University, Umeå, Sweden.
VIB-UGent Center for Medical Biotechnology, VIB, Ghent, Belgium.
Physiol Plant. 2024 May-Jun;176(3):e14401. doi: 10.1111/ppl.14401.
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.
类半胱天冬氨酸蛋白酶存在于植物、真菌和原生生物中。虽然类半胱天冬氨酸蛋白酶与细胞死亡的关联在多种生物中都有研究，但它们的天然底物在很大程度上仍是未知的。在这里，我们使用基于质谱的降解组学方法，在对照条件和盐胁迫下，探索了绿色淡水藻类衣藻中存在的两种类半胱天冬氨酸蛋白酶 CrMCA-I 和 CrMCA-II 的体内蛋白水解景观。CrMCA-I 和 CrMCA-II 在类半胱天冬氨酸蛋白酶突变体中的切割事件的比较揭示了独特的切割偏好和底物特异性。降解组分析表明，预测的类半胱天冬氨酸蛋白酶底物与衣藻细胞的生理学及其在盐胁迫下的适应有关。功能富集分析表明，CrMCA-I 参与了羧酸的分解代谢，而 CrMCA-II 在光合作用和翻译中发挥重要作用。总之，我们的研究结果表明，在盐胁迫响应期间，两种类半胱天冬氨酸蛋白酶在衣藻中具有不同的细胞功能。
