Platelet-derived growth factor (PDGF) is a mitogen for mesenchyme- and gliaderived
cells. PDGF consists of two chains, A and B, which dimerize to form
functionally distinct isoforms, PDGF-AA, PDGF-AB and PDGF-BB. These three
isoforms bind with different affinities to two receptor types, PDGFR-α and -β,
which are endowed with protein tyrosine kinase domains. PDGFR-α can bind
to both A and B subunits of PDGF, while PDGFR-β can only bind the B subunit.
Ligand binding promotes either homo- or heterodimerization of the PDGF
receptors in a specific manner. PDGF-AA induces the dimerization of two α
receptors, PDGF-AB induces dimerization of αα and αβ and PDGF-BB induces
the formation of three types of dimers, αα, αβ and ββ. The genes encoding
PDGFR-α and -β map to human chromosome 4q11-q13 and 5q31-32, respectively.
The expressed α and β receptor proteins migrate at 170 and 180 kDa,
respectively, by SDS-PAGE. Translocation of the PDGFR-β gene with the Tel
gene is linked to chronic myelomonocytic leukemia (CMML), a myelodysplastic
syndrome, and demonstrates the oncogenic potential of the PDGF receptors.