Cell-type-specific ATF6α programs regulate epithelial mitochondrial homeostasis and pericyte remodeling during physiological and exposure-accelerated lung aging

Proteostasis declines with lung aging, while the role of the Unfolded Protein Response (UPR) in lung aging and age-associated pulmonary diseases remains understudied. We investigated how deficiency in the UPR sensor ATF6 affects physiological and smoke exposure-accelerated lung aging. ATF6 -deficient mice exhibited accelerated alveolar simplification, a sign of lung parenchymal aging, which was exacerbated by smoking. Nevertheless, small airway vascular fibrotic remodeling, a prominent smoking-induced pathology, was not evident in smoke-exposed ATF6 -deficient mice. Mechanistically, these divergent phenotypes arose from cell-type-specific ATF6 programs. In alveolar epithelial type 2 cells (AEC2s), the facultative progenitors of the lung parenchyma, ATF6 maintained mitochondrial bioenergetics and sustained efficient redifferentiation into alveolar epithelial type 1 cells (AEC1s). In lung pericytes, ATF6 promoted extravasation, redifferentiation into myofibroblast-like cells, and production of collagens 1 and 3. These findings identify ATF6 as a cell-type-specific regulator of differentiation programs during lung aging and highlight the need to study ATF6 under defined physiological and pathological contexts before therapeutically targeting this pathway.