A human osteosarcoma cell line secretes a growth factor structurally related to a homodimer of PDGF A-chains.
Platelet-derived growth factor (PDGF), as purified from fresh human platelets, is a protein of relative molecular mass (Mr) 30,000 composed of two disulphide-linked subunit chains of similar size, named A and B (ref. 1). The dimer structure of PDGRF seems to be important for its biological effects, as reduction irreversibly inactivates the factor; it is not known, however, whether PDGF exists as a heterodimer or as a mixture of homodimers. Amino-acid sequence analysis has revealed that the A- and B-chains of human PDGF are related to each other, and that the B-chain is almost identical to part of the v-sis gene product of simian sarcoma virus (SSV). There is experimental evidence that a PDGF-like protein is indeed operational in SSV-induced transformation and the biologically active v-sis product is probably structurally similar to a putative dimer of PDGF B-chains. PDGF-like growth factors and/or a 4.2-kilobase (kb) c-sis transcript are present in several transformed mammalian cell lines and in certain nontransformed cells; cloned c-sis complementary DNA from human T cells transformed with human T-lymphotropic virus (HTLV) or from human endothelial cells contains the coding sequence for a putative PDGF B-chain precursor, but apparently lacks PDGF A-chain sequences. We have previously partially purified and characterized a PDGF-like growth factor from U-2 OS cells (osteosarcoma-derived growth factor, ODGF) and shown that this factor has structural, functional and immunological characteristics in common with PDGF. We describe here a procedure for the preparation of homogeneous ODGF, and provide evidence that this factor, which binds to the PDGF receptor, has a structure similar to a homodimer of PDGF A-chains.
Heldin
C H
CH
Johnsson
A
A
Wennergren
S
S
Wernstedt
C
C
Betsholtz
C
C
Westermark
B
B
D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D006133:Growth Substances / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D012516:Osteosarcoma / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor
D006133:Growth Substances; D046911:Macromolecular Substances; D010982:Platelet-Derived Growth Factor