Moesin Regulates the Trafficking of Nascent Clathrin-coated Vesicles

• Published in: The Journal of biological chemistry Vol. 284; no. 4; pp. 2419 - 2434
• Main Authors: Barroso-González, Jonathan, Machado, José-David, García-Expósito, Laura, Valenzuela-Fernández, Agustín
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 23.01.2009; American Society for Biochemistry and Molecular Biology
• Subjects: Clathrin-Coated Vesicles - metabolism; HeLa Cells; Humans; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Protein Binding; Protein Transport; Receptors, Transferrin - metabolism; RNA, Small Interfering - genetics; Transferrin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M805311200

Clathrin-coated vesicles are responsible for the trafficking of several internalized biological cargos. We have observed that the endogenous F-actin-linker moesin co-distributes with constitutive components of clathrin-coated structures. Total internal reflection fluorescence microscopy studies have shown that short interference RNA of moesin enhances the lateral movement of clathrin-coated structures and provokes their abnormal clustering. The aggregation of clathrin-coated structures has also been observed in cells overexpressing N-moesin, a dominant-negative construct unable to bind to F-actin. Only overexpressed moesin constructs with an intact phosphatidylinositol 4,5-bisphosphate-binding domain co-distribute with clathrin-coated structures. Hence, this N-terminal domain is mostly responsible for moesin/clathrin-coated structure association. Biochemical endosome fractioning together with total internal reflection fluorescence microscopy comparative studies, between intact cells and plasma-membrane sheets, indicate that moesin knockdown provokes the accumulation of endocytic rab5-clathrin-coated vesicles carrying the transferrin receptor. The altered trafficking of these endocytic rab5-clathrin-coated vesicles accounts for a transferrin receptor recycling defect that reduces cell-surface expression of the transferrin receptor and increases the amount of sequestered transferrin ligand. Therefore, we propose that moesin is a clathrin-coated vesicle linker that drives cargo trafficking and acts on nascent rab5-clathrin-coated vesicles by simultaneously binding to clathrin-coated vesicle-associated phosphatidylinositol 4,5-bisphosphate and actin cytoskeleton. Hence, functional alterations of moesin may be involved in pathological disorders associated with clathrin-mediated internalization or receptor recycling.