title: Regulation of Jak2 tyrosine kinase by protein kinase C during macrophage differentiation of IL-3-dependent myeloid progenitor cells.
abstract: Differentiation of macrophages from myeloid progenitor cells depends on a discrete balance between cell growth, survival, and differentiation signals. Interleukin-3 (IL-3) supports the growth and survival of myeloid progenitor cells through the activation of Jak2 tyrosine kinase, and macrophage differentiation has been shown to be regulated by protein kinase C (PKC). During terminal differentiation of macrophages, the cells lose their mitogenic response to IL-3 and undergo growth arrest, but the underlying signaling mechanisms have remained elusive. Here we show that in IL-3-dependent 32D myeloid progenitor cells, the differentiation-inducing PKC isoforms PKC-alpha and PKC-delta specifically caused rapid inhibition of IL-3-induced tyrosine phosphorylation. The target for this inhibition was Jak2, and the activation of PKC by 12-O-tetradecanoyl-phorbol-13-acetate treatment also abrogated IL-3-induced tyrosine phosphorylation of Jak2 in Ba/F3 cells. The mechanism of this regulation was investigated in 32D and COS7 cells, and the inhibition of Jak2 required catalytic activity of PKC-delta and involved the phosphorylation of Jak2 on serine and threonine residues by the associated PKC-delta. Furthermore, PKC-delta inhibited the in vitro catalytic activity of Jak2, indicating that Jak2 was a direct target for PKC-delta. In 32D cells, the inhibition of Jak2 either by PKC-delta, tyrosine kinase inhibitor AG490, or IL-3 deprivation caused a similar growth arrest. Reversal of PKC-delta-mediated inhibition by the overexpression of Jak2 promoted apoptosis in differentiating 32D cells. These results demonstrate a PKC-mediated negative regulatory mechanism of cytokine signaling and Jak2, and they suggest that it serves to integrate growth-promoting and differentiation signals during macrophage differentiation. (Blood. 2000;95:1626-1632)
authors.affiliation: Laboratory of Molecular Immunology, Institute of Medical Technology, University of Tampere, Tampere, Finland.
authors.forename: P E
authors.initials: PE
authors.lastname: Kovanen
authors.forename: I
authors.initials: I
authors.lastname: Junttila
authors.forename: K
authors.initials: K
authors.lastname: Takaluoma
authors.forename: P
authors.initials: P
authors.lastname: Saharinen
authors.forename: L
authors.initials: L
authors.lastname: Valmu
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: O
authors.initials: O
authors.lastname: Silvennoinen
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002384:Catalysis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000502:physiology; D004261:DNA Replication; D004789:Enzyme Activation; D004790:Enzyme Induction; D007377:Interleukin-3 / Q000494:pharmacology*; D007527:Isoenzymes / Q000502:physiology*; D053614:Janus Kinase 2; D008264:Macrophages / Q000166:cytology* / Q000201:enzymology; D051379:Mice; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: D007377:Interleukin-3; D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; C497259:Prkcd protein, mouse; C497256:Prkce protein, mouse; D011505:Protein-Tyrosine Kinases; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D013755:Tetradecanoylphorbol Acetate