Non-autophagic Golgi-LC3 lipidation facilitates TFE3 stress response against Golgi dysfunction.

Lipidated ATG8/LC3 proteins are recruited to single membrane compartments as well as autophagosomes, supporting their functions. Although recent studies have shown that Golgi-LC3 lipidation follows Golgi damage, its molecular mechanism and function under Golgi stress remain unknown. Here, by combining DLK1 overexpression as a new strategy for induction of Golgi-specific LC3 lipidation, and the application of Golgi-damaging reagents, we unravel the mechanism and role of Golgi-LC3 lipidation. Upon DLK1 overexpression, LC3 is lipidated on the Golgi apparatus in an ATG12-ATG5-ATG16L1 complex-dependent manner; a post-Golgi trafficking blockade is the primary cause of this lipidation. During Golgi stress, ATG16L1 is recruited through its interaction with V-ATPase for Golgi-LC3 lipidation. After post-Golgi trafficking inhibition, TFE3, a key regulator of the Golgi stress response, is translocated to the nucleus. Defects in LC3 lipidation disrupt this translocation, leading to an attenuation of the Golgi stress response. Together, our results reveal the mechanism and unexplored function of Golgi-LC3 lipidation in the Golgi stress response.