Involvement of PI3K in PKCepsilon-mediated oncogenic signal in rat colonic epithelial cells.
We have recently demonstrated that overexpression of PKCepsilon is oncogenic in colonic epithelial cells. To test whether PI3K might be an upstream effector of PKCepsilon in cell transformation, we have overexpressed the p110alpha PI3K subunit in non-transformed D/WT colonic epithelial cells. Transfectants displayed the major in vitro features of transformed cells. Interestingly, no transformation occurred when p110alpha was co-transfected with a dead-kinase PKCepsilon mutant. The p85alpha subunit of PI3K, displaying a dominant-negative-like effect, was then transfected in PKCepsilon-transformed D/epsilon cells. The transformed profile of these cells was markedly reduced. To identify which by-products of PI3K might be involved in cell transformation we have transfected the D/WT cell line with cDNAs encoding the PI3 kinases hVps34 and C2beta. Overexpression of hVps34 did not cause cell transformation. Conversely, in vitro transformation was observed when C2beta was transfected into D/WT cells. These results indicate that phosphatidylinositol-3 monophosphate does not seem to be involved in cell transformation, and that phosphatidylinositol-3,4 bisphosphate and phosphatidylinositol-3,4,5 trisphosphate are more likely involved in this process. Thus, our data support the hypothesis of a linkage between PI3K and PKCepsilon, and indicate that PI3K may act as a source of second messengers responsible for oncogenic activation of PKCepsilon.
Marras
E
E
Dipartimento di Biologia Strutturale e Funzionale, Universita degli Studi dell'Insubria, Via J.H. Dunant 3, I-21100 Varese, Italy.
Concari
P
P
Cortellezzi
L
L
Dondi
D
D
De Eguileor
M
M
Perletti
G
G
D000818:Animals; D020134:Catalytic Domain; D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D003106:Colon / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D003114:Colony-Forming Units Assay; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D005822:Genetic Vectors / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D009369:Neoplasms / Q000235:genetics / Q000473:pathology; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D021122:Protein Subunits; D051381:Rats; D015398:Signal Transduction; D014162:Transfection
D007527:Isoenzymes; D021122:Protein Subunits; D019869:Phosphatidylinositol 3-Kinases; C497257:Prkce protein, rat; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon