RTK

RTK or Receptor Tyrosine Kinase is a high-affinity cell surface receptor for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins.

Structure

RTKs are composed of an extracellular domain, which is able to bind a specific growth factor, a single transmembrane helix, and an intracellular domain, which possesses tyrosine kinase activity. The extracellular domain is often rich in cysteine residues, which form disulfide bonds to stabilize the receptor structure.

Function

Upon binding of a ligand to the extracellular domain, RTKs form dimers. Dimerization leads to a close proximity of the intracellular domains stimulating autophosphorylation of tyrosines within the tyrosine kinase domains of the RTK monomers. This autophosphorylation leads to the activation of the RTKs, initiating a variety of intracellular signaling cascades.

Signaling Pathways

RTKs are key regulators of normal cellular processes, but may also lead to cancer and other diseases when they are overexpressed or mutated. RTKs activate several signaling pathways, including the RAS/MAPK, PI3K/AKT and JAK/STAT pathways.

Clinical Significance

Several RTKs have been classified as oncogenes, and mutations in these genes often lead to uncontrolled cell growth and cancer. Therefore, RTKs have become popular targets for the development of anti-cancer drugs.