The unfolded protein response (UPR) is a cellular mechanism that helps maintain protein quality within the endoplasmic reticulum (ER). When proteins misfold or accumulate, the UPR activates to restore normal function by halting protein synthesis, enhancing the production of chaperone proteins, and promoting the degradation of misfolded proteins. This process is crucial for cell health and function. If the stress on the ER is too severe or prolonged, the UPR can trigger programmed cell death, or apoptosis, to prevent damaged cells from causing harm. The UPR is essential in various conditions, including neurodegenerative diseases and diabetes, where protein misfolding is prevalent.