- Ligand-specific activation of HER4/p180erbB4, a fourth member of the epidermal growth factor receptor family. Plowman, G.D., Culouscou, J.M., Whitney, G.S., Green, J.M., Carlton, G.W., Foy, L., Neubauer, M.G., Shoyab, M. Proc. Natl. Acad. Sci. U.S.A. (1993)