LC3-linked Golgi-bypass exocytosis fortifies epithelial barrier defense

Cells dynamically regulate membrane protein delivery to meet physiological demands, yet how external cues rapidly mobilize unconventional Golgi-bypass exocytic routes in vivo remains unclear. Here we define LC3/Atg8-associated carrier exocytosis (LACES), a conserved program that couples microbial cues to accelerated surface delivery. In the Caenorhabditis elegans intestine, phenazine-1-carboxamide (PCN) triggers VPS-34-dependent PtdIns3P generation at ILE-1/ERGIC-53 subdomains, enabling Atg8ylation on preexisting single-membrane RAB-8 carriers. This route accelerates delivery of the ABC transporter PGP-1 and improves host survival during infection, while operating independently of the unfolded protein response, canonical macroautophagy/autophagy initiation modules, and LC3-associated phagocytosis regulators. The pathway is engaged by multiple extracellular bacteria and also functions in mammalian epithelia, where PCN increases apical ΔF508-CFTR delivery in polarized Caco-2 cysts with measurable functional improvement and enhances LC3-RAB8 interactions in mouse intestinal epithelium. These findings establish a conserved LC3-linked Golgi-bypass route and illustrate how microbial cues can rapidly rewire epithelial membrane trafficking to fortify barrier defense.Abbreviations: ABC: ATP-binding cassette; BFA: brefeldin A; CFTR: CF transmembrane conductance regulator; ERGIC: ER-Golgi intermediate compartment; FRAP: fluorescence recovery after photobleaching; LACES: LC3/Atg8-Associated Carrier Exocytosis; LAP: LC3-associated phagocytosis; PCA: phenazine-1-carboxylic acid; PCN: phenazine-1-carboxamide; PYO: pyocyanin; 1-HP: 1-hydroxyphenazine; ROS: reactive oxygen species; UPR: unfolded protein response