NoxO1 promotes endosome formation and reduces intracellular vesicle processing.

NADPH oxidase organizer 1 (NoxO1) is known as a scaffold cytoplasmic subunit of the reactive oxygen species (ROS) forming Nox1 complex. We previously identified an interaction between NoxO1 and Erbin, a cytosolic scaffold protein that associates with Epidermal Growth Factor Receptor (EGFR), but its ROS-independent roles remain poorly understood. Here, we demonstrate that NoxO1 overexpression remodels the endolysosomal system by expanding early endosomes and lysosomes. A calibrated six-compartment ordinary differential equation model of EGFR trafficking predicts a slowed down intracellular trafficking: NoxO1 overexpression increased internalization rates by 14 % while reducing degradative sorting by 48 %, lysosomal transfer by 24 %, and final degradation by 41 %. Using fluorescent cargo (EGF and BSA), we confirmed enhanced internalization and cargo accumulation in lysosomes, supporting the idea of prolonged lysosomal retention in NoxO1 overexpressing cells. Mechanistically, NoxO1 activated transcription factor EB (TFEB), the master regulator of lysosomal biogenesis, in an Erbin-dependent but ROS independent manner. Proximity ligation assays revealed spatial association of NoxO1, Erbin, EGFR, and TFEB, suggesting a multi-protein regulatory complex. Genetic ablation of Erbin abolished NoxO1-induced increases in early endosome (EEA1) and lysosome (LAMP1) markers, confirming Erbin's essential role. In conclusion, via its interaction with Erbin NoxO1 promotes activation of TFEB, contributes to lysosome formation while delaying cargo degradation.