ER stress occurs when the endoplasmic reticulum (ER), a cell organelle responsible for protein folding and processing, becomes overwhelmed. This can happen due to various factors, such as high demand for protein production, genetic mutations, or environmental stressors. When the ER is stressed, it struggles to maintain proper function, leading to an accumulation of misfolded proteins. To cope with ER stress, cells activate a protective response known as the unfolded protein response (UPR). This response aims to restore normal function by halting protein translation, degrading misfolded proteins, and enhancing the production of molecular chaperones. If the stress persists, however, it can lead to cell dysfunction or even cell death.