{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Receptor tyrosine-protein kinase erbB-3, also known as HER-3 (Human Epidermal Growth Factor Receptor 3), is a membrane bound protein that in humans is encoded by the ERBB3 gene. HER-3 has been shown to bind the ligands heregulin and NRG-2. Ligand binding causes a change in conformation that allows for dimerization, phosphorylation, and activation of signal transduction. HER-3 can heterodimerize with any of the other three ErbB family members."}]},{"type":"paragraph","children":[{"type":"text","value":"During human development, HER-3 is expressed in skin, bone, muscle, nervous system, heart, lungs, and intestinal epithelium and is expressed in normal adult human gastrointestinal tract, reproductive system, skin, nervous system, urinary tract, and endocrine system. HER-3 is overexpressed in a variety of tumors including breast, stomach, pancreas, and colon. While no evidence has been found that HER-3 overexpression, constitutive activation, or mutation alone is oncogenic, the protein as a heterodimerization partner, most critically with HER-2, is implicated in growth, proliferation, resistance, and the promotion of invasion and metastasis."}]}]}