The Arabidopsis J-Protein AtDjC5 Facilitates Thermotolerance Likely by Aiding in the ER Stress Response.

AtDjC5 belongs to the J-protein family in Arabidopsis thaliana. Its biological functions remain unclear. In this study, we examined the roles of AtDjC5 in resisting heat stress using reverse genetic analysis. After the seedlings were exposed directly to 44 °C for 90 min, AtDjC5 knockout seedlings displayed decreases in the survival rate, membrane system stability, and cell vitality compared to WT seedlings, indicating that AtDjC5 is involved in plant basal thermotolerance. The AtDjC5 knockout seedlings pre-exposed to 37 °C for 30 min exhibited decreases in the survival rate and total chlorophyll contents and increased cell death when they were subsequently exposed to 45 °C compared to the WT seedlings, indicating that AtDjC5 plays an important role in plant acquired thermotolerance. AtDjC5 was found to localize to the endoplasmic reticulum. The expression of the AtDjC5 gene was induced by heat and TM (an ER stress inducer) treatment. Furthermore, we found that the knockout of AtDjC5 inhibited ER stress-induced autophagy and the expression of ER stress-related genes. Taken together, these results suggest that AtDjC5 facilitates thermotolerance, likely by aiding in the ER stress response.

Cisplatin-induced necroptosis in TNFα dependent and independent pathways.

Cisplatin is a chemotherapeutic drug for treatment of many solid tumors. It has been shown to induce apoptosis and/or necrosis in different types of cancer cells. However, the underlying mechanisms remain elusive. In this study, we provide evidences that cisplatin induces necroptosis in receptor-interacting protein 3 (RIP3)-expressing cell lines, but not in cell lines lacking RIP3 protein expression. Deficiency of core components of necroptotic pathway, RIP1, RIP3, or mixed lineage kinase domain-like protein (MLKL) blocked cisplatin-induced cell death in L929 cells. This phenomenon is dependent on RIP1/RIP3/MLKL necrosome formation and translocation to mitochondria-associated membrane (MAM), but only partially via autocrine production of tumor necrosis factor α (TNFα). Moreover, we demonstrate that the mitochondrial permeability transition pore opening (mPTP) opening and reactive oxygen species (ROS) generation is a critical downstream event of the formation of necrosome in cisplatin-induced necroptosis, which is TNFα independent. Deficiency of cyclophilin-D (CypD) partially reduced cisplatin-induced cell death, indicating CypD mediated-mPTP opening plays an important role during cisplatin-induced necroptosis. Both deletion of CypD and TNFα completely blocked cisplatin-induced cell death, suggesting that cisplatin could induce necroptosis through TNFα dependent and independent pathway. These findings provide new insight into the molecular mechanisms underlying cisplatin-induced necroptosis.