Selective activation of the JNK/AP-1 pathway in Fas-mediated apoptosis of rheumatoid arthritis synoviocytes.
OBJECTIVE
To evaluate the Fas-dependent signaling pathway, we examined the involvement of protein tyrosine phosphorylation and the DNA binding activity of AP-1 in rheumatoid arthritis (RA) cultured synovial cells.


METHODS
The number of dead cells was counted after treatment with anti-Fas antibody in the presence of protein tyrosine kinase or phosphatase inhibitor. Protein tyrosine phosphorylation in synoviocytes after Fas ligation was examined by immunoblot and immunoprecipitation analyses. The DNA binding activity of AP-1 was examined by electrophoretic mobility shift assay.


RESULTS
Treatment with the protein tyrosine phosphatase inhibitor, orthovanadate, significantly enhanced the apoptosis of RA synoviocytes after Fas ligation. Ligation of the Fas molecule on RA synoviocytes induced a rapid tyrosine phosphorylation of JNK (c-Jun amino-terminal kinase) and formation of the AP-1 transcription factor.


CONCLUSIONS
Our results strongly suggest that the JNK/AP-1 signaling pathway is activated during the process of Fas-mediated apoptosis of RA synovial cells.
Okamoto
K
K
Institute of Medical Science, St. Marianna University School of Medicine, Miyamae-ku, Kawasaki, Japan.
Fujisawa
K
K
Hasunuma
T
T
Kobata
T
T
Sumida
T
T
Nishioka
K
K
D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000473:pathology* / Q000503:physiopathology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology; D004586:Electrophoresis; D006801:Humans; D015151:Immunoblotting; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D013583:Synovial Membrane / Q000473:pathology*; D018808:Transcription Factor AP-1 / Q000502:physiology*; D014638:Vanadates / Q000494:pharmacology; D019014:fas Receptor / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D018808:Transcription Factor AP-1; D019014:fas Receptor; D014638:Vanadates; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases