ErbB4/HER4

ErbB4/HER4 is an EGFR/ErbB-family receptor tyrosine kinase that mediates responses to neuregulins and other EGF-like growth factors[1]. Mechanistically, ErbB4 regulates cardiovascular and neural development and mammary gland differentiation through ligand-dependent receptor signaling[1]. Alternative splicing generates four structurally and functionally distinct ErbB4 isoforms, defined by extracellular juxtamembrane domains and cytoplasmic tails[1]. Compared with related ErbB receptors, ErbB4 shows isoform-specific signaling: both cytoplasmic isoforms couple to Shc-MAPK, whereas one isoform cannot activate PI3K-Akt[1]. In mammary models, NRG3 regulates epithelial progenitor cell positioning, and activation of ErbB4 JM-a CYT-1 leads to mammary epithelial cell spreading and migration[2]. In 3D mammary organoids, culture conditions including Neuregulin1 and R-spondin 1 support maintenance and expansion for 2.5 months[3]. In cancer research, ERBB4 has context-dependent roles, with ERBB4 homodimers reviewed as tumor suppressive and ERBB4-EGFR or ERBB4-ERBB2 heterodimers reviewed as oncogenic[4]. For inhibitor design, structural work defined activation and inhibition mechanisms of the HER4/ErbB4 kinase, and imidazothiazole derivatives were reported as potent and selective ErbB4 inhibitors[5][6].