Association of tetraspanin CD9 with transmembrane TGFα confers alterations in cell-surface presentation of TGFα and cytoskeletal organization (Publication with Expression of Concern. See vol. 135, 2022) (Publication with Expression of Concern. See vol. 135, 2022)

Ligand presentation is a major determinant of receptor activation. The epidermal growth factor receptor (EGFR), a tyrosine kinase receptor, is activated by growth factors of the transforming growth factor alpha (TGF alpha) family. The tetraspanin CD9 interacts with transmembrane TGFa and decreases its ectodomain shedding to release soluble TGF alpha. Here we report that CD9 has a role in the maturation of transmembrane TGF alpha and its stabilization at the cell surface, and in the cell-surface distribution in polarized epithelial cells. Furthermore, coexpression of CD9 and TGF alpha confers changes in cytoskeletal organization with a decrease in actin stress fibers and focal adhesions, and changes in RhoA and Rac1 GTPase activity. These alterations are reversed by blocking EGFR signaling. Finally, we demonstrate changes in cell adhesion and migration resulting from coexpression of TGF alpha with CD9. These results provide insight into the role of CD9 in the presentation of TGF alpha in epithelial and carcinoma cells, whose physiology is driven by ligand-induced EGFR activation.