Induction of granulocyte-macrophage colony-stimulating factor by a new cytokine, ML-1 (IL-17F), via Raf I-MEK-ERK pathway.
BACKGROUND
ML-1 (IL-17F) is a recently discovered cytokine, and its function remains elusive. GM-CSF is a crucial cytokine for the maturation of various cell types and regulates allergic airway inflammation.


OBJECTIVE
The functional effect of ML-1 in the expression of GM-CSF was investigated.


METHODS
The levels of gene and protein expression in normal human bronchial epithelial cells (NHBEs) in the presence or absence of various kinase inhibitors or, in some cases, of a Raf1 dominant-negative mutant were determined by RT-PCR and ELISA, respectively. Western blotting was performed to investigate kinase activation.


RESULTS
The results showed first that ML-1 induces, in a time-dependent and dose-dependent manner, the gene and protein expression for GM-CSF NHBEs, which are associated with activation of Raf1 and MAP kinase kinase (MEK) kinases. Selective MEK inhibitors, PD98059 and U0126, and Raf1 kinase inhibitor I significantly inhibited ML-1-induced GM-CSF production. Furthermore, overexpression of Raf1 dominant-negative mutants inhibited IL-17F-induced GMCSF expression. The combination of PD98059 and Raf1 kinase inhibitor I completely blocked GM-CSF production, whereas 2 protein kinase C inhibitors, Ro-31-7549 and GF109203X, and a phosphatidylinositol 3-kinase inhibitor, LY294002, showed no inhibitory effect.


CONCLUSIONS
These findings suggest that ML-1 induces GM-CSF expression through the activation of the Raf1-MEK-extracellular signal-regulated kinase 1/2 pathway.
Kawaguchi
Mio
M
Asthma and Allergy Center, Johns Hopkins University, Baltimore, MD 21224-6801, USA.
Kokubu
Fumio
F
Odaka
Miho
M
Watanabe
Shin
S
Suzuki
Shintaro
S
Ieki
Koushi
K
Matsukura
Satoshi
S
Kurokawa
Masatsugu
M
Adachi
Mitsuru
M
Huang
Shau-Ku
SK
D001980:Bronchi / Q000378:metabolism; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D020381:Interleukin-17 / Q000494:pharmacology*; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf / Q000502:physiology*; D015398:Signal Transduction
C440021:IL17F protein, human; D020381:Interleukin-17; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human