Proliferating or differentiating stimuli act on different lipid-dependent signaling pathways in nuclei of human leukemia cells.
Previous results have shown that the human promyelocytic leukemia HL-60 cell line responds to either proliferating or differentiating stimuli. When these cells are induced to proliferate, protein kinase C (PKC)-beta II migrates toward the nucleus, whereas when they are exposed to differentiating agents, there is a nuclear translocation of the alpha isoform of PKC. As a step toward the elucidation of the early intranuclear events that regulate the proliferation or the differentiation process, we show that in the HL-60 cells, a proliferating stimulus (i.e., insulin-like growth factor-I [IGF-I]) increased nuclear diacylglycerol (DAG) production derived from phosphatidylinositol (4,5) bisphosphate, as indicated by the inhibition exerted by 1-O-octadeyl-2-O-methyl-sn-glycero-3-phosphocholine and U-73122 (1-[6((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione), which are pharmacological inhibitors of phosphoinositide-specific phospholipase C. In contrast, when HL-60 cells were induced to differentiate along the granulocytic lineage by dimethyl sulfoxide, we observed a rise in the nuclear DAG mass, which was sensitive to either neomycin or propranolol, two compounds with inhibitory effect on phospholipase D (PLD)-mediated DAG generation. In nuclei of dimethyl sulfoxide-treated HL-60 cells, we observed a rise in the amount of a 90-kDa PLD, distinct from PLD1 or PLD2. When a phosphatidylinositol (4,5) bisphosphate-derived DAG pool was generated in the nucleus, a selective translocation of PKC-beta II occurred. On the other hand, nuclear DAG derived through PLD, recruited PKC-alpha to the nucleus. Both of these PKC isoforms were phosphorylated on serine residues. These results provide support for the proposal that in the HL-60 cell nucleus there are two independently regulated sources of DAG, both of which are capable of acting as the driving force that attracts to this organelle distinct, DAG-dependent PKC isozymes. Our results assume a particular significance in light of the proposed use of pharmacological inhibitors of PKC-dependent biochemical pathways for the therapy of cancer disease.
Neri
Luca M
LM
Dipartimento di Morfologia ed Embriologia, Sezione di Anatomia Umana Normale, Università di Ferrara, 44100 Ferrara, Italy.
Bortul
Roberta
R
Borgatti
Paola
P
Tabellini
Giovanna
G
Baldini
Giovanna
G
Capitani
Silvano
S
Martelli
Alberto M
AM
D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology; D018922:HL-60 Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D064546:Protein Kinase C beta; D015398:Signal Transduction / Q000502:physiology*; D012997:Solvents / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D004075:Diglycerides; D007527:Isoenzymes; D012997:Solvents; C005356:sphingosine phosphorylcholine; D010767:Phosphorylcholine; D000431:Ethanol; D007334:Insulin-Like Growth Factor I; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D010739:Phospholipase D; D013110:Sphingosine; D013755:Tetradecanoylphorbol Acetate; D004121:Dimethyl Sulfoxide