The unfolded protein response (UPR) is a critical cellular signaling pathway that helps maintain endoplasmic reticulum (ER) homeostasis by responding to stressors such as protein misfolding, oxidative stress, and inflammatory signals. The UPR is essential for the proper folding and secretion of proteins and plays a significant role in various diseases, including metabolic disorders, neurodegenerative diseases, inflammatory conditions, and cancer. The UPR consists of three main branches: IRE1α, PERK, and ATF6α, each contributing to different aspects of cellular adaptation and survival. IRE1α is involved in splicing of XBP1 mRNA, which enhances ER protein folding and degradation. PERK regulates protein synthesis by phosphorylating eIF2α, which reduces global translation and promotes the expression of stress-responsive genes. ATF6α, upon ER stress, is processed to activate transcription factors that regulate ER function and stress responses. These pathways work together to maintain cellular homeostasis, but their dysregulation can lead to apoptosis and disease. In diabetes, the UPR is crucial for β-cell function and insulin production. Mutations in PERK or other UPR components can lead to β-cell failure and diabetes. The UPR also plays a role in metabolic syndrome by influencing lipid and glucose homeostasis. In cancer, the UPR supports tumor growth under hypoxic conditions and can promote tumor progression by enhancing angiogenesis and cell survival. In neurodegenerative diseases, the UPR is involved in the pathogenesis of conditions such as Alzheimer's and Parkinson's. The UPR's role in these diseases is complex and disease-specific, with some pathways promoting cell survival while others contribute to cell death. In infectious and inflammatory diseases, the UPR is involved in immune responses and can influence the progression of conditions such as atherosclerosis and inflammatory bowel disease. The UPR is a dynamic and adaptable system that responds to various physiological and pathological conditions. Understanding the UPR's role in disease is crucial for developing therapeutic strategies targeting the UPR to treat a wide range of conditions. Current research focuses on modulating UPR activity to achieve therapeutic benefits, particularly in diseases where UPR dysregulation contributes to pathogenesis.The unfolded protein response (UPR) is a critical cellular signaling pathway that helps maintain endoplasmic reticulum (ER) homeostasis by responding to stressors such as protein misfolding, oxidative stress, and inflammatory signals. The UPR is essential for the proper folding and secretion of proteins and plays a significant role in various diseases, including metabolic disorders, neurodegenerative diseases, inflammatory conditions, and cancer. The UPR consists of three main branches: IRE1α, PERK, and ATF6α, each contributing to different aspects of cellular adaptation and survival. IRE1α is involved in splicing of XBP1 mRNA, which enhances ER protein folding and degradation. PERK regulates protein synthesis by phosphorylating eIF2α, which reduces global translation and promotes the expression of stress-responsive genes. ATF6α, upon ER stress, is processed to activate transcription factors that regulate ER function and stress responses. These pathways work together to maintain cellular homeostasis, but their dysregulation can lead to apoptosis and disease. In diabetes, the UPR is crucial for β-cell function and insulin production. Mutations in PERK or other UPR components can lead to β-cell failure and diabetes. The UPR also plays a role in metabolic syndrome by influencing lipid and glucose homeostasis. In cancer, the UPR supports tumor growth under hypoxic conditions and can promote tumor progression by enhancing angiogenesis and cell survival. In neurodegenerative diseases, the UPR is involved in the pathogenesis of conditions such as Alzheimer's and Parkinson's. The UPR's role in these diseases is complex and disease-specific, with some pathways promoting cell survival while others contribute to cell death. In infectious and inflammatory diseases, the UPR is involved in immune responses and can influence the progression of conditions such as atherosclerosis and inflammatory bowel disease. The UPR is a dynamic and adaptable system that responds to various physiological and pathological conditions. Understanding the UPR's role in disease is crucial for developing therapeutic strategies targeting the UPR to treat a wide range of conditions. Current research focuses on modulating UPR activity to achieve therapeutic benefits, particularly in diseases where UPR dysregulation contributes to pathogenesis.