The kinase-impaired ErbB3 is known to form active heterodimers with other members of the ErbB family, most notably the ligand binding-impaired ErbB2.

[5] During human development, ERBB3 is expressed in skin, bone, muscle, nervous system, heart, lungs, and intestinal epithelium.

Subdomains II and IV are cysteine-rich and most likely contribute to protein conformation and stability through the formation of disulfide bonds.

[13] This heterodimer conformation allows the signaling complex to activate multiple pathways including the MAPK, PI3K/Akt, and PLCγ.

While no evidence has been found that ErbB3 overexpression, constitutive activation, or mutation alone is oncogenic,[18] the protein as a heterodimerization partner, most critically with ErbB2, is implicated in growth, proliferation, chemotherapeutic resistance, and the promotion of invasion and metastasis.

ErbB3 null mouse embryos show severely underdeveloped atrioventricular valves, leading to death at embryonic day 13.5.