V-ATPase-Driven Lysosomal Activation Orchestrates MEK2-Induced Endothelial Reprogramming

Direct lineage reprogramming holds therapeutic promise but often depends on transcription factor overexpression, resulting in unstable phenotypes. Here, we describe a novel strategy to convert fibroblasts into endothelial-like cells by activating lysosomal activity. Constitutively active MEK2 induces an endothelial gene program via sustained MAPK/ERK signaling, leading to enhanced vacuolar ATPase (V-ATPase) activity, lysosomal acidification, extracellular matrix degradation, and angiogenic behavior. V-ATPase inhibition impairs these effects, whereas pharmacologic activation with EN6 recapitulates key features of reprogramming and promotes nuclear translocation of TFEB, a master lysosomal regulator. Consistently, TFEB overexpression–particularly a phospho-deficient mutant–boosts lysosomal function and endothelial gene expression. These findings define a MAPK–V-ATPase–TFEB axis that drives endothelial reprogramming and highlight the lysosome as a central hub for cell fate transitions, offering an organelle-centric framework for regenerative medicine.