A Rapid Bioassay for Platelet–Derived Growth Factor β-Receptor Tyrosine Kinase Function

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Abstract
We have extended a melanophore–based bioassay for G–protein coupled receptors to include the functional expression of the murine platelet–derived growth factor (PDGF) β–receptor. The homodimeric ligand PDGF–BB induced activation of the transiently expressed receptor in melanophore cells. This led to dose dependent pigment dispersion whereas it did not induce pigment dispersion in wild type cells. The effective concentration of PDGF–BB giving half–maximal pigment dispersion (EC50) was 1 nM after 30 minutes exposure. PDGF–AA had no abiltity to induce pigment dispersion in melanophore cells transiently expressing the β–PDGF receptor. PDGF–BB–induced pigment dispersion could be blocked by the bisindolylmaleimide Ro 31–8220 which is an inhibitor of protein kinase C isoenzymes. Functional expression of the PDGF β–receptor extends the use of the pigment translocation assay to include transmembrane signaling receptor tyrosine kinases. It opens the opportunity for the discovery of potent agonists and antagonists through massive drug screening and investigations of functional ligand–receptor interactions for single transmembrane domain receptors.