Regulation of Akt/PKB by phosphatidylinositol 3-kinase-dependent and -independent pathways in B-cell chronic lymphocytic leukemia cells: role of protein kinase C{beta}.
Apoptosis of B cell chronic lymphocytic leukemia (B-CLL) cells is regulated by the PI-3K-Akt pathway. In the present work, we have analyzed the mechanisms of Akt phosphorylation in B-CLL cells. Freshly isolated cells present basal Akt phosphorylation, which is PI-3K-dependent, as incubation with the PI-3K inhibitor LY294002 decreased Ser-473 and Thr-308 phosphorylation in most samples analyzed (seven out of 10). In three out of 10 cases, inhibition of protein kinase C (PKC) inhibited basal Akt phosphorylation. Stromal cell-derived factor-1alpha, IL-4, and B cell receptor activation induced PI-3K-dependent Akt phosphorylation. PMA induced the phosphorylation of Akt at Ser-473 and Thr-308 and the phosphorylation of Akt substrates, independently of PI-3K in B-CLL cells. In contrast, PKC-mediated phosphorylation of Akt was PI-3K-dependent in normal B cells. Finally, a specific inhibitor of PKCbeta blocked the phosphorylation and activation of Akt by PMA in B-CLL cells. Taken together, these results suggest a model in which Akt could be activated by two different pathways (PI-3K and PKCbeta) in B-CLL cells.
Barragán
Montserrat
M
Unitat de Bioquímica, Departament de Ciències Fisiològiques II, IDIBELL-Universitat de Barcelona, Campus de Bellvitge, Pavelló de Govern, L'Hospitalet de Llobregat, Barcelona E-08907, Spain.
de Frias
Mercè
M
Iglesias-Serret
Daniel
D
Campàs
Clara
C
Castaño
Esther
E
Santidrián
Antonio F
AF
Coll-Mulet
Llorenç
L
Cosialls
Ana M
AM
Domingo
Alicia
A
Pons
Gabriel
G
Gil
Joan
J
D017209:Apoptosis / Q000187:drug effects; D002273:Carcinogens / Q000494:pharmacology; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology*; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D018121:Receptors, Cytokine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051057:Proto-Oncogene Proteins c-akt; D018121:Receptors, Cytokine; D013755:Tetradecanoylphorbol Acetate; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one