SESN1 (sestrin 1) functions as a stress-responsive metabolic regulator with multiple cellular roles. As an intracellular leucine sensor, SESN1 negatively regulates mTORC1 signaling through the GATOR complex, binding to GATOR2 in leucine-depleted conditions to prevent mTORC1 activation 1. Beyond mTORC1 regulation, SESN1 controls cell proliferation and death through STAT3 suppression by downregulating the PTPRD phosphatase 2. The protein serves as a crucial immune homeostasis regulator by targeting STING1 for autophagic degradation through SQSTM1/p62, balancing antiviral responses with autoimmune prevention 3. In vascular biology, SESN1 protects endothelial cells against oxidative stress and inflammation by activating AMPK/SIRT1 signaling and suppressing LOX1 expression 45. Clinically, SESN1 expression correlates with prognosis in TP53-mutated head and neck squamous cell carcinoma 6 and mediates resistance to cisplatin and hyperthermia treatments through ROS regulation 7. The protein's protective functions against oxidative stress and its role in autophagy regulation make it significant for cancer therapy and cardiovascular disease management.