Syntaxin 9 Is Enriched in Skin Hair Follicle Epithelium and Interacts With the Epidermal Growth Factor Receptor

The study identified syntaxin 9 (Syn 9) as a novel molecule enriched in the epithelial cells of skin hair follicles and the stomach lining, interacting specifically with the epidermal growth factor receptor (EGFR). Syn 9 was associated with plasma and endosomal membranes and was developmentally regulated, suggesting a role in the development or maintenance of epithelial structures. Overexpression of Syn 9 in A431 and HeLa cells disrupted EGF endocytosis, indicating its specific involvement in EGFR trafficking, while not affecting transferrin receptor endocytosis. The findings suggested that Syn 9 might inhibit an early step in EGFR endocytosis, potentially affecting the fusion of EGFR-containing vesicles with early endosomes, highlighting its potential role in regulating EGFR trafficking and signaling in epithelial tissues.