Tyrosine kinase signaling pathway

The tyrosine kinase signaling pathway, also known as TK or RTK pathways when referring specifically to receptors involved,[1] comprises a series of intracellular biochemical events initiated by activation of enzymes called tyrosine kinases, which transfer phosphate groups from ATP onto tyrosines on substrate proteins. This post-translational modification acts as an “on/off” switch regulating diverse cellular processes including proliferation, survival/apoptosis balance, differentiation and metabolism. Tyrosine kinases can be either cytoplasmic enzymes or membrane-bound receptors (receptor tyrosine kinases, RTKs). Upon ligand binding—often peptide hormones like EGF—RTKs dimerize and autophosphorylate their intracellular domains. This creates docking sites for adaptor/scaffold proteins that propagate signals through cascades such as RAS/MAPK and PI3K/Akt pathways.[5] Dysregulation through mutation/overexpression leads directly to oncogenesis; thus many modern cancer therapies inhibit key nodes/proteins within these cascades using small-molecule inhibitors or monoclonal antibodies.[1][2][6] However—as “tyrosine kinase signaling pathway” refers collectively to all these interconnected reactions—it is not itself considered a single molecular drug target suitable for structured pharmacological annotation.[1]

Other names

TK signalingProtein tyrosine kinase cascadeReceptor tyrosine kinase (RTK) pathwaysTyrosine phosphorylation pathways

Drugs targeting this system typically act by: - Inhibiting ATP binding at the catalytic site of tyrosine kinases/receptors ("kinase inhibitors"). - Blocking ligand binding or dimerization at extracellular domains ("monoclonal antibodies"). - Preventing downstream phosphorylation events required for signal propagation. These mechanisms block aberrant signal transduction that drives uncontrolled cell growth/proliferation in cancer.