Torin2

In eukaryotes, target of rapamycin (TOR), a conserved protein sensor kinase, integrates diverse environmental cues, including growth factor signals, energy availability, and nutritional status, to direct cell growth. In plants, TOR is activated by light and sugars and regulates a wide range of cellular processes, including protein synthesis and metabolism. Fatty acid (FA) synthesis is a key to membrane biogenesis that is required for cell growth. To elucidate the primary regulatory role(s) of TOR in lipid metabolism, we followed FA and lipid changes in plants with altered TOR protein levels or activity for short durations, using Nicotiana benthamiana leaves, Arabidopsis seedlings, and Brassica napus cell suspension cultures. Transient expression of TOR significantly elevated the levels of total FA (TFA) in N. benthamiana leaves. Conversely, treatment of Arabidopsis seedlings with the TOR-specific inhibitor Torin 2 for 1 d caused significant reductions in FA and membrane lipids. Similarly, incubating oil–producing B. napus suspension culture cells with Torin 2 for 8 h led to significant decreases in the levels of TFA and triacylglycerol. The results from 3 independent systems presented here establish that TOR positively regulates lipid synthesis in plants, consistent with its role in animals. Furthermore, RNA-seq analysis of Torin 2-treated Arabidopsis seedlings showed that TOR promotes the upregulation of several genes involved in de novo FA synthesis while downregulating several genes involved in lipid turnover, which we propose as a mechanistic explanation for its promotion of lipid synthesis and accumulation.

Bisphenol A (BPA) is a common endocrine disruptor chemical that is widely used in the production of food plastic packaging, and it has been shown to potentially harm the reproductive system. However, the specific mechanism by which BPA induces apoptosis of Leydig cells (LCs) and inhibits testosterone synthesis in these cells is unclear. In the present study, TM3 cells were used as an experimental model in combination with a reactive oxygen species (ROS) scavenger (N-acetylcysteine), Caspase-3 inhibitor (Ac-DEVD-CHO), autophagy activator (Torin2), and autophagy inhibitor (Chloroquine) to investigate the potential mechanisms by which BPA causes TM3 cell damage in vitro. BPA treatment increased ROS production, which led to a marked decrease in antioxidant enzyme activity and the expression levels of antioxidant-related genes and proteins in TM3 cells. Upregulated ROS cause excessive opening of the mitochondrial permeability transition pore and significantly decrease the expression levels of genes related to membrane potential and mitochondrial function in TM3 cells. The release of cytochrome C from damaged mitochondria into the cytoplasm activated a Caspase cascade reaction. In addition, excessive ROS levels impaired autophagic degradation by inhibiting the fusion of autophagosomes with lysosomes. These abnormalities eventually induced apoptosis and inhibited testosterone synthesis in TM3 cells. The collective findings suggest that BPA induces apoptosis and interferes with testosterone synthesis in TM3 cells by upregulating ROS production, thereby activating the mitochondrial apoptotic pathway and inhibiting autophagic flux. These findings provide novel mechanistic insights into male reproductive toxicity caused by BPA exposure.