Monocyte 15-lipoxygenase expression is regulated by a novel cytosolic signaling complex with protein kinase C delta and tyrosine-phosphorylated Stat3.
Our previous studies demonstrated that the IL-13-induced 15-lipoxygenase expression in primary human monocytes is regulated by the activation of both Stat1 and Stat3 and by protein kinase C (PKC)delta. IL-13 stimulated the phosphorylation of Stat3 on both Tyr705 and Ser727. In this study we show that IL-13 induces the association of PKCdelta with Stat3, not with Stat1, and is required for Stat3 Ser727 phosphorylation. We found a novel IL-13-dependent cytosolic signaling complex of PKCdelta and tyrosine-phosphorylated Stat3. A tyrosine kinase inhibitor blocked PKCdelta association with Stat3 as well as Stat3 Ser727 phosphorylation. We therefore hypothesized that tyrosine phosphorylation was required for Stat3 interaction with PKCdelta and subsequent PKCdelta-dependent phosphorylation of Stat3 Ser727. We developed an efficient transfection protocol for human monocytes. Expression of Stat3 containing a mutation in Tyr705 inhibited the association of PKCdelta with Stat3 and blocked Stat3 Ser727 phosphorylation, whereas transfection with wild-type Stat3 did not. Furthermore, by transfecting monocytes with Stat3 containing mutations in Tyr705 or Ser727 or with wild-type Stat3, we demonstrated that both Stat3 tyrosine and serine phosphorylations are required for optimal binding of Stat3 with DNA and maximal expression of 15-lipoxygenase, an important regulator of inflammation and apoptosis.
Bhattacharjee
Ashish
A
Department of Cell Biology, Cleveland Clinic Foundation, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA.
Xu
Bo
B
Frank
David A
DA
Feldman
Gerald M
GM
Cathcart
Martha K
MK
D021581:Active Transport, Cell Nucleus / Q000276:immunology; D001093:Arachidonate 15-Lipoxygenase / Q000096:biosynthesis* / Q000235:genetics; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D009000:Monocytes / Q000201:enzymology* / Q000378:metabolism; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000502:physiology*; D011994:Recombinant Proteins / Q000494:pharmacology; D050794:STAT1 Transcription Factor / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D014443:Tyrosine / Q000378:metabolism*
D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D014443:Tyrosine; D012694:Serine; D001093:Arachidonate 15-Lipoxygenase; D051745:Protein Kinase C-delta