STARD3 is a sterol-binding protein that mediates cholesterol transport from the endoplasmic reticulum (ER) to endosomes 123. The transport mechanism is triggered by phosphorylation of its FFAT motif, enabling membrane tethering between the ER and late endosomes through interaction with VAP proteins (VAPA and VAPB) 435. This tethering facilitates cholesterol redistribution to endosomal membranes at the expense of the cell membrane 3. STARD3 also binds other lipids, notably lutein, a xanthophyll carotenoid that accumulates in retinal and brain tissue, where it correlates with cognitive function in infants 678. While STARD3 may mediate cholesterol transport to mitochondria, current evidence supports ER-endosome transport as its primary function 39. Clinically, STARD3 is co-amplified with HER2 in breast cancer, where high expression predicts worse survival outcomes in HER2+ tumors and correlates with disease progression 1011. Additionally, STARD3 regulates airway epithelial inflammation in COPD through cholesterol redistribution and mitochondrial dynamics regulation 12.