Platelet-derived growth factor BB (PDGF) stimulates DNA synthesis through a mechanism that is at least partially dependent upon Src family tyrosine kinases, although the signal transduction pathway downstream of Src is poorly understood. We have studied the signaling between Src and different protein kinase C (PKC) isoforms and its possible role in the regulation of PDGF-stimulated DNA synthesis. We found that Src promoted the tyrosine phosphorylation of PKCδ, and its subsequent degradation. Enforced expression of PKCδ inhibited PDGF-stimulated DNA synthesis, whereas expression of PKCα and PKCε did not, a finding consistent with a model in which PKCδ negatively regulates G1-to-S-phase progression. We used mutagenesis to map a critical Src phosphorylation site on PKCδ to tyrosine 311. A mutant form of PKCδ in which tyrosine 311 was replaced with phenylalanine (Y311F) was more stable in the presence of Src, suggesting that Src-induced degradation was a direct result of PKCδ tyrosine phosphorylation. We conclude that PKCδ is downstream of Src but is unlikely to play a positive role in the signaling pathway by which Src promotes DNA synthesis.
|Original language||English (US)|
|Number of pages||11|
|Journal||Cell Growth and Differentiation|
|State||Published - Apr 1 1999|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology