Calcium/calmodulin-dependent protein kinase II (CaMKII) regulates tumour necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis of fibroblast-like synovial cells (FLS) by phosphorylation of Akt.
OBJECTIVE
We tried to determine whether calcium/calmodulin-dependent protein kinase II (CaMKII) regulates tumour necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis of fibroblast-like synovial cells (FLS).


METHODS
CaMKII expression in FLS was studied by both western blotting and real time reverse transcription polymerase chain reaction (RT-PCR). TRAIL-mediated apoptosis of FLS was quantified by disruption of mitochondrial transmembrane potential (DeltaPsim), Leu-Glu-His-Asp (IETD) ase activity and DNA degradation. Involvement of CaMKII and other kinases, including extracellular signal-regulated kinase (ERK), p38, c-Jun N-terminal kinase (JNK) and Akt during TRAIL-mediated apoptosis of FLS was estimated by the use of specific each kinase chemical inhibitor.


RESULTS
Predominant expression of delta and gamma isoform of CaMKII, especially delta isoform, was determined in cultured FLS. TRAIL rapidly induced apoptosis of FLS as well as the phosphorylation of extracellular signal-regulated kinase (ERK), p38, c-Jun N-terminal kinase (JNK) and Akt. Chemical kinase inhibitor toward CaMKII and Akt significantly augmented TRAIL-mediated apoptosis of FLS whereas those toward ERK, p38 and JNK did not. Notably, CaMKII chemical inhibitor abrogated TRAIL-induced phosphorylation of Akt. Elevation of Leu-Glu-His-Asp (IETD) ase activity was associated with the apoptotic phenomena, which was almost suppressed by IETD competitive peptides.


CONCLUSIONS
Our results suggest a first observation that CaMKII regulates TRAIL-mediated apoptosis of FLS through Akt, standing an upstream of caspase-8-dependent cascades. Furthermore, CaMKII is suggested to be a new therapeutic target molecule of rheumatoid arthritis (RA).
Fujikawa
K
K
Unit of Translational Medicine, Department of Immunology and Rheumatology, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
Kawakami
A
A
Tanaka
F
F
Iwamoto
N
N
Tamai
M
M
Eguchi
K
K
D000368:Aged; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008875:Middle Aged; D010766:Phosphorylation / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*
D012333:RNA, Messenger; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D051057:Proto-Oncogene Proteins c-akt; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D053181:Caspase 8; D002118:Calcium