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. May also be activated by CSPG5. Involved in the regulation of myeloid cell differentiation. 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, PA2G4, GRB7, MYOC and MUC1. Found in a ternary complex with NRG1 and ITGAV:ITGB3 or ITGA6:ITGB4 (By similarity). The cytoplasmic part of the receptor may interact with the SH2 or SH3 domains of many signal-transducing proteins. Autophosphorylated. Ligand-binding increases phosphorylation on tyrosine residues and promotes its association with the p85 subunit of phosphatidylinositol 3-kinase. Belongs to the protein kinase superfamily. Tyr protein kinase family. EGF receptor subfamily.