ATG conjugation-dependent/independent mechanisms underlie lysosomal stress-induced TFEB regulation.

TFEB, a master regulator of autophagy and lysosomal biogenesis, is activated by several cellular stresses including lysosomal damage, but its underlying mechanism is unclear. TFEB activation during lysosomal damage depends on the ATG conjugation system, which mediates lipidation of ATG8 proteins. Here, we newly identify ATG conjugation-independent TFEB regulation that precedes ATG conjugation-dependent regulation, designated Modes I and II, respectively. We reveal unique regulators of TFEB in each mode: APEX1 in Mode I and CCT7 and/or TRIP6 in Mode II. APEX1 interacts with TFEB independently of the ATG conjugation system, and is required for TFEB stability, while both CCT7 and TRIP6 accumulate on lysosomes during lysosomal damage, and interact with TFEB mainly in ATG conjugation system-deficient cells, presumably blocking TFEB activation. TFEB activation by several other stresses also involves either Mode I or Mode II. Our results pave the way for a unified understanding of TFEB regulatory mechanisms from the perspective of the ATG conjugation system under a variety of cellular stresses.