ATF6, or Activating Transcription Factor 6, is a protein that plays a key role in the unfolded protein response (UPR) pathway. The UPR is a cellular stress response mechanism that is activated when the endoplasmic reticulum (ER) is overwhelmed with misfolded or unfolded proteins. When activated, ATF6 translocates to the Golgi apparatus where it is cleaved by proteases, releasing its transcriptionally active domain. This domain then translocates to the nucleus and activates the expression of genes involved in protein folding, ER-associated degradation, and other processes to help restore ER homeostasis. Research in the ATF6 pathway often focuses on its role in ER stress response, its regulation, and its potential as a therapeutic target for diseases related to ER stress.