Simultaneous induction of stimulatory and inhibitory signals by PDGF

Platelet‐derived growth factor (PDGF) exerts its effects on cells via binding to structurally similar α‐ and β‐tyrosine kinase receptors. Ligand binding induces receptor dimerization and autophosphorylation which allows docking of SH2 domain containing signal transduction molecules. At least 10 different SH2 domain molecules bind in a specific manner to 11 identified autophosphorylated tyrosine residues in the PDGF β‐receptor, thereby initiating signaling pathways leading to cell growth and motility. Available information indicates that there is considerable cross‐talk between different signaling pathways, and that stimulatory and inhibitory signals often are initiated in parallel.