Simultaneous induction of stimulatory and inhibitory signals by PDGF.

Platelet-derived growth factor (PDGF) exerts its effects on cells via binding to structurally similar alpha- and beta-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 beta-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.