ERBB3

ERBB3, also known as HER3 (human epidermal growth factor receptor 3), is a member of the epidermal growth factor receptor (EGFR/ERBB) family of receptor tyrosine kinases. This protein family has been implicated in a variety of cancers, including breast, lung, and prostate cancer.

Structure

ERBB3 is a single-pass type I membrane protein. It is composed of an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular domain with tyrosine kinase activity. The extracellular domain of ERBB3 contains two cysteine-rich subdomains, which are necessary for ligand binding and receptor dimerization.

Function

ERBB3 is unique among the ERBB proteins in that it lacks intrinsic tyrosine kinase activity. Instead, it relies on heterodimerization with other ERBB proteins, particularly ERBB2/HER2, to activate downstream signaling pathways. Upon ligand binding, ERBB3 undergoes a conformational change that allows it to dimerize with another ERBB protein. This dimerization leads to the activation of the intracellular kinase domain of the partner protein, which in turn phosphorylates tyrosine residues on ERBB3. These phosphorylated residues serve as docking sites for signaling proteins, leading to the activation of pathways involved in cell proliferation, survival, and differentiation.

Clinical significance

Mutations and overexpression of ERBB3 have been implicated in a variety of cancers. In particular, ERBB3 has been shown to play a critical role in the development and progression of breast cancer, lung cancer, and prostate cancer. In these cancers, ERBB3 often works in concert with ERBB2/HER2, which is frequently amplified or overexpressed. As such, ERBB3 has emerged as a potential therapeutic target in these cancers.

See also

• Epidermal growth factor receptor
• ERBB
• ERBB2
• ERBB4