Activating transcription factor 6 (ATF6)

Activating transcription factor 6 (ATF6) is a type II transmembrane protein located in the endoplasmic reticulum. It is one of the three primary ER stress sensors and regulators of the unfolded protein response (UPR), alongside PERK and IRE1. ATF6 exists as two main isoforms, ATF6α and ATF6β, which differ in transcriptional activation potency and stability. Under normal conditions, ATF6 is retained in the ER by interaction with the chaperone GRP78/BiP. Upon accumulation of unfolded proteins (cellular stress), GRP78 dissociates, allowing ATF6 to be transported to the Golgi apparatus, where it is proteolytically cleaved by site-1 and site-2 proteases. The cleaved cytosolic fragment translocates to the nucleus, triggering transcription of genes involved in protein folding (chaperones), ERAD, and cell survival. Prolonged or severe ER stress can shift ATF6 downstream signaling from protective to pro-apoptotic.\n\nDisease relevance is pronounced in conditions characterized by aberrant proteostasis, misfolded protein accumulation, and chronic cellular stress. Experimental modulators of ATF6 are under investigation for metabolic, degenerative, inflammatory, and fibrotic diseases. The lack of high-resolution crystal structure for ATF6 presents ongoing challenges for rational drug design.

Other names

ATF6αATF6βUnfolded protein response (UPR) factorER stress transducer

Modulating ATF6 activation and nuclear translocation to either enhance protective UPR/adaptive chaperone expression or suppress pathological prolonged ER stress signaling leading to apoptosis. Small molecules may block or enhance ATF6 cleavage, nuclear import, or DNA binding.