title: Role of protein kinase C in phosphorylation of vinculin in adriamycin-resistant HL-60 leukemia cells.
abstract: In response to phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA), HL-60 cells differentiate to macrophage-like cells and exhibit the ability to phosphorylate vinculin in vitro. Adriamycin-resistant HL-60 (HL-60/ADR) cells similarly demonstrate this characteristic without prior treatment with TPA. Since protein kinase C (PK-C) is a cellular TPA receptor, we have examined the role of this enzyme in the inherent ability of HL-60/ADR cells to phosphorylate vinculin. DEAE-cellulose chromatography of cell extracts revealed that HL-60/ADR cells contained 2-fold more PK-C than did the parental cell line. All PK-C activity was found in the cytosol of wild type HL-60 cells, whereas 85% of PK-C activity was cytosolic and 15% was membrane-bound in HL-60/ADR cells. After a 2-day treatment with 10 nM TPA, PK-C activity was reduced 80-90% in both cell lines regardless of its intracellular distribution. Immunoblotting of cell extracts from HL-60/ADR cells or HL-60 cells following treatment with TPA revealed increased levels of a 52-kDa species of similar mass to M-kinase. Coincident with these changes after TPA treatment was a reduction in Ca2+ and phospholipid-independent phosphorylation of vinculin in vitro in extracts from HL-60/ADR cells, whereas HL-60 cells exhibited an elevation of this phosphoprotein. The phosphorylation of vinculin in TPA-treated HL-60 cells or untreated HL-60/ADR cells was blocked by antibodies to protein kinase C. These results suggest that it is not the absolute level of protein kinase C but rather the proteolytic activation of PK-C to a Ca2+ and phospholipid-independent form which is associated with the utilization of vinculin as an endogenous substrate.
mesh_terms: D002454:Cell Differentiation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology*; D004351:Drug Resistance; D010450:Endopeptidases / Q000502:physiology; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism* / Q000473:pathology; D009124:Muscle Proteins / Q000378:metabolism*; D015260:Neprilysin; D010766:Phosphorylation; D011493:Protein Kinase C / Q000276:immunology / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016596:Vinculin
chemical_list: D009124:Muscle Proteins; D016596:Vinculin; D004317:Doxorubicin; D011493:Protein Kinase C; D010450:Endopeptidases; D015260:Neprilysin; D013755:Tetradecanoylphorbol Acetate