Receptor binding of PDGF-AA and PDGF-BB, and the modulation of PDGF receptors by TGF-beta, in human periodontal ligament cells.
The growth factors PDGF-AA and PDGF-BB have previously been shown to be potent mitogens for human periodontal ligament (hPDL) cells in vitro. Additionally, the mitogenic response to PDGF-AA has been shown to be specifically inhibited by TGF-beta. The purpose of the present investigation was to examine the binding of PDGF-AA and PDGF-BB, and the modulation of PDGF binding by TGF-beta, in hPDL cells. Scatchard analysis identified an average of 32,000 PDGF-AA high-affinity binding sites per cell with a dissociation constant (Kd) of 0.66 nM and an average of 36,000 PDGF-BB binding sites per cell with a dissociation constant (kd) of 0.44 nM. After treatment with TGF-beta, the receptor number for PDGF-AA was found to specifically decrease by approximately 50%, with no change in binding affinity. This reduced number of binding sites was shown to correlate with both a decrease in levels of receptor tyrosine phosphorylation and a decreased number of alpha receptor subunits. Northern blot analysis identified the TGF-beta-mediated decrease in PDGF alpha receptor subunit mRNA levels. PDGF-BB showed little change in the number of binding sites or in the binding affinity with TGF-beta treatment, and the data were consistent with an increase in the number of beta receptor subunits. These results demonstrate nearly equivalent numbers of receptors for both PDGF-AA and PDGF-BB in hPDL cells. Also, modulation of PDGF binding, by TGF-beta, was shown to result in a reduced number of alpha receptor subunits with an increase in the number of beta receptor subunits.
Department of Periodontics, University of Texas Health Science Center at San Antonio 78284.
T W
TW
Oates
K N
KN
Kose
J F
JF
Xie
D T
DT
Graves
J M
JM
Collins
D L
DL
Cochran
D002478:Cells, Cultured; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D010513:Periodontal Ligament / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D011505:Protein-Tyrosine Kinases; D017479:Receptors, Platelet-Derived Growth Factor