Protein kinase C-delta is an important signaling molecule in insulin-like growth factor I receptor-mediated cell transformation.
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.
Li
W
W
Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892, USA. Liwe@dc37a.nci.nih.gov
Jiang
Y X
YX
Zhang
J
J
Soon
L
L
Flechner
L
L
Kapoor
V
V
Pierce
J H
JH
Wang
L H
LH
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D004789:Enzyme Activation; D015870:Gene Expression; D015683:Gene Products, gag / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051745:Protein Kinase C-delta; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D015683:Gene Products, gag; D007527:Isoenzymes; D014443:Tyrosine; C497259:Prkcd protein, mouse; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D011493:Protein Kinase C; D051745:Protein Kinase C-delta