Related Experiment Videos
Protein kinase C-delta is an important signaling molecule in insulin-like growth factor I receptor-mediated cell
1Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA. Liwe@dc37a.nci.nih.gov
Abstract:
To investigate the potential role of protein kinase C-delta (PKC-delta) in insulin-like growth factor I receptor (IGF-IR)-mediated cell transformation, an oncogenic gag-IGF-IR beta-fusion receptor lacking the entire extracellular domain, which was designated NM1, and a full-length IGF-IR were coexpressed with either wild-type PKC-delta (PKC-deltaWT) or an ATP-binding mutant of PKC-delta (PKC-deltaK376R) in NIH 3T3 fibroblasts. While overexpression of PKC-deltaWT did not affect NM1- and IGF-IR-induced focus and colony formation of NIH 3T3 cells, expression of PKC-deltaK376R severely impaired these events. In contrast, NM1-mediated cell growth in monolayer was not affected by coexpressing PKC-deltaK376R. PKC-deltaWT and PKC-deltaK376R were constitutively phosphorylated on a tyrosine residue(s) in the NM1- and IGF-IR-expressing cells and were associated with them in an IGF-I-independent manner. Activated IGF-IR was able to phosphorylate purified PKC-delta in vitro and stimulated its kinase activity. Furthermore, the level of endogenous PKC-delta protein was up-regulated through transcriptional activation in response to long-term IGF-IR activation. Taken together, our results demonstrate that PKC-delta plays an important role in IGF-IR-mediated cell transformation, probably via association of the receptor with PKC-delta and its activation through protein up-regulation and tyrosine phosphorylation. Competition with endogenous PKC-delta for NM1 and IGF-IR association by PKC-deltaK376R is probably an important mechanism underlying the PKC-deltaK376R-mediated inhibition of cell transformation by NM1 and IGF-IR.
Insights
Protein kinase C-delta (PKC-delta) is crucial for insulin-like growth factor I receptor (IGF-IR)-mediated cell transformation. A mutant form of PKC-delta inhibits this process by competing for receptor association, highlighting PKC-delta
Area of Science:
- Cell Biology
- Molecular Biology
- Oncology
Background:
- Insulin-like growth factor I receptor (IGF-IR) signaling is implicated in cell transformation and cancer.
- Protein kinase C-delta (PKC-delta) is a signaling molecule with diverse cellular functions.
- The interplay between IGF-IR and PKC-delta in cell transformation remains incompletely understood.
Purpose of the Study:
- To investigate the role of PKC-delta in IGF-IR-mediated cell transformation.
- To determine how wild-type (PKC-deltaWT) and mutant PKC-delta (PKC-deltaK376R) affect IGF-IR signaling and cell transformation.
- To elucidate the mechanisms by which PKC-delta influences IGF-IR-driven oncogenesis.
Main Methods:
- Coexpression of oncogenic gag-IGF-IR beta-fusion receptor (NM1) or full-length IGF-IR with PKC-deltaWT or PKC-deltaK376R in NIH 3T3 fibroblasts.
- Assessment of focus and colony formation to evaluate cell transformation.
- Analysis of protein-cell association, phosphorylation, and kinase activity.
- Investigation of endogenous PKC-delta protein levels and transcriptional activation.
Main Results:
- PKC-deltaK376R, but not PKC-deltaWT, severely impaired NM1- and IGF-IR-induced focus and colony formation.
- NM1-mediated cell growth in monolayer was unaffected by PKC-deltaK376R.
- PKC-deltaWT and PKC-deltaK376R associated with NM1 and IGF-IR in an IGF-I-independent manner and were tyrosine phosphorylated.
- Activated IGF-IR phosphorylated and stimulated PKC-delta kinase activity in vitro.
- Endogenous PKC-delta protein levels were upregulated by long-term IGF-IR activation.
Conclusions:
- PKC-delta plays a significant role in IGF-IR-mediated cell transformation.
- PKC-delta activation, via receptor association, protein upregulation, and tyrosine phosphorylation, is critical for transformation.
- PKC-deltaK376R inhibits transformation by competing with endogenous PKC-delta for association with NM1 and IGF-IR.