Overexpression of the Csk homologous kinase facilitates phosphorylation of Akt/PKB in MCF-7 cells.
The serine/threonine kinase Akt has recently been the focus of intense research. Akt activation requires the phosphorylation of both Thr-308 and Ser-473. Src kinase was shown to induce activation of Akt, while Lyn kinase seems to inhibit this activation. In the present study, we investigated the effect of overexpressing the Csk homologous kinase (CHK), an inhibitor of Src-family kinases, on the phosphorylation of Akt induced by two different factors: heregulin or cisplatin. We used MCF-7 cells stably overexpressing the wild-type CHK [CHK(wt)] or dead-kinase CHK [CHK(dk)]. We observed that in MCF-7 CHK(wt) cells Lyn kinase activity was more profoundly inhibited than Src kinase activity. When the cells were stimulated with heregulin or cisplatin, Akt phosphorylation occurred more rapidly in MCF-7 CHK(wt) cells in comparison to the other clones used. Interestingly, MCF-7 CHK(wt) cells in vitro were markedly more resistant to cisplatin than the other clones used in the experiments, and surprisingly chemical inhibition of Akt phosphorylation did not influence this resistance. In summary, our results show facilitation of Akt phosphorylation by the overexpression of CHK, and provide new insight into the putative role of CHK in human cancer.
Zagozdzon
Radoslaw
R
Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
Bougeret
Cécile
C
Fu
Yigong
Y
Avraham
Hava Karsenty
HK
D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000201:enzymology* / Q000473:pathology; D000081247:CSK Tyrosine-Protein Kinase; D002455:Cell Division / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D006801:Humans; D066298:In Vitro Techniques; D009361:Neoplasm Invasiveness; D020890:Neuregulin-1 / Q000494:pharmacology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D016392:Proto-Oncogene Proteins pp60(c-src); D015398:Signal Transduction; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D019061:src-Family Kinases / Q000378:metabolism
D000970:Antineoplastic Agents; D020890:Neuregulin-1; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; C085377:MATK protein, human; D016392:Proto-Oncogene Proteins pp60(c-src); C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D002945:Cisplatin