Extracellular signal-regulated protein kinase (ERK)-dependent and ERK-independent pathways target STAT3 on serine-727 in human neutrophils stimulated by chemotactic factors and cytokines.
STAT3 (signal transducer and activator of transcription 3) is a latent transcription factor that is activated by tyrosine phosphorylation (Tyr-705) in cells stimulated with cytokines or growth factors. Recent studies suggest that one or more cytoplasmic serine kinases also phosphorylate STAT3 and are necessary for maximal gene activation. Here we demonstrate, with a site-specific antibody, that STAT3 is phosphorylated on Ser-727 in human neutrophils stimulated with chemotactic factors (N-formyl-methionyl-leucyl-phenylalanine and complement C5a), cytokines [granulocyte/macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF)], or a protein kinase C activator (PMA). (2-Amino-3'-methoxyphenyl)oxanaphthalen-4-one (PD 98059), an inhibitor of extracellular signal-regulated protein kinase (ERK) activation, blocked the serine phosphorylation of STAT3 induced by chemotactic factors or PMA. The drug was less effective on cytokines: it virtually abolished the response to GM-CSF that occurred 5 min after stimulation but only partly decreased those at 15-30 min and did not appreciably alter responses to G-CSF regardless of incubation time. 1-(5-Isoquinolinylsulphonyl)-2-methylpiperazine dihydrochloride (H7), an inhibitor of a putative STAT3 serine kinase, and 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl) 1H-imidazole (SB 203580), an inhibitor of p38 mitogen-activated protein (MAP) kinase, did not dampen any of these serine phosphorylation responses. We propose that neutrophils use both ERK-dependent and ERK-independent pathways to phosphorylate Ser-727 on STAT3. The former pathway is recruited by all ERK-activating stimuli, whereas the latter pathway uses an undefined serine kinase and is recruited selectively by cytokines.
Department of Internal Medicine, Section on Infectious Diseases, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
M
M
Kuroki
J T
JT
O'Flaherty
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002630:Chemotactic Factors / Q000494:pharmacology*; D015936:Complement C5a / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D050796:STAT3 Transcription Factor; D012694:Serine / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D002630:Chemotactic Factors; D016207:Cytokines; D004268:DNA-Binding Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D016179:Granulocyte Colony-Stimulating Factor; D014443:Tyrosine; D012694:Serine; D015936:Complement C5a; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate