Tyrosine-protein kinase that plays an essential role as cell surface receptor for neuregulins. Binds to neuregulin-1 (NRG1) and is activated by it; ligand-binding increases phosphorylation on tyrosine residues and promotes its association with the p85 subunit of phosphatidylinositol 3-kinase (PubMed:20682778). May also be activated by CSPG5 (PubMed:15358134). Involved in the regulation of myeloid cell differentiation (PubMed:27416908). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Monomer and homodimer. Heterodimer with each of the other ERBB receptors (Potential). Interacts with CSPG5 (PubMed:15358134). Interacts with GRB7 (PubMed:9516479). Interacts with MUC1 (PubMed:12939402). Interacts with MYOC (By similarity). Interacts with isoform 2 of PA2G4 (PubMed:11325528, PubMed:16832058). Found in a ternary complex with NRG1 and ITGAV:ITGB3 or ITGA6:ITGB4 (PubMed:20682778). Epithelial tissues and brain. Overexpressed in a subset of human mammary tumors. The cytoplasmic part of the receptor may interact with the SH2 or SH3 domains of many signal-transducing proteins. Autophosphorylated (PubMed:20351256). Ligand-binding increases phosphorylation on tyrosine residues and promotes its association with the p85 subunit of phosphatidylinositol 3-kinase (PubMed:20682778). The disease is caused by variants affecting the gene represented in this entry. Disease susceptibility may be associated with variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the protein kinase superfamily. Tyr protein kinase family. EGF receptor subfamily.