Receptor Tyrosine Kinases

Understanding how groups of initially equivalent cells develop into complex tissues containing many cell types is an important goal for biologists. In recent years, it has become increasingly clear that the developmental fate of individual cells is often established by activating transmembrane receptors of the Receptor Tyrosine Kinase (RTK) family. RTKs dimerize in response to binding their specific ligand(s) (van der Geer et al. 1994). Dimerization leads to autophosphorylation of the RTK as well as the phosphorylation of other signaling molecules on specific tyrosine residues. As a result of these phosphorylation events, a number of intracellular signal transduction cascades are initiated. Perhaps the most important consequence of RTK activation is an increase in the activity of Ras, and thus, MAP kinase (MAPK). Activated MAPK can modulate the activity of various transcription factors and other cellular proteins.