Roles of PKC, PI3K and JNK in multiple transduction of CCN2/CTGF signals in chondrocytes.
CCN2/connective tissue growth factor (CCN2/CTGF) is known to promote both the proliferation and differentiation of chondrocytes, which actions are mediated by ERK and p38 MAPK, respectively. In this study, we first re-evaluated the involvement of multiple MAPKs therein and found that JNK also mediated such CCN2 signals. Thereafter, we further analyzed the roles of upstream kinases. The involvement of PKC, PI3K and PKA in the CCN2 signaling to promote the maturation, proliferation and terminal differentiation of a human chondrocytic cell line, HCS-2/8 and rabbit primary growth cartilage cells was investigated. As a result, the PKC inhibitor calphostin C repressed all of the effects of CCN2, which were represented by increased synthesis of DNA and proteoglycans and the display of alkaline phosphatase activity. In addition, evaluation of the effect of the PI3K inhibitor wortmannin disclosed the contribution of PI3K in transducing CCN2 signals to promote chondrocyte hypertrophy. This signal was known to be mediated by PKB, which was translocated into the nucleus upon CCN2 stimulation. Of note, calphostin C showed inhibitory effects on the activation of p38 MAPK, ERK and also PKB, whereas it exerted no effect on JNK activation. These results suggest that PKC is a driver of multiple signal transducing kinases that promote the proliferation and differentiation of chondrocytes. The requirement of PI3K in transmitting the signal for terminal differentiation and PKC-independent signaling pathways for the promotion of chondrocytic growth and differentiation, which was mediated by JNK, were also uncovered.
Yosimichi
Gen
G
Department of Biochemistry and Molecular Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8525, Japan.
Kubota
Satoshi
S
Nishida
Takashi
T
Kondo
Seiji
S
Yanagita
Takeshi
T
Nakao
Kyouji
K
Takano-Yamamoto
Teruko
T
Takigawa
Masaharu
M
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D055513:Connective Tissue Growth Factor; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004789:Enzyme Activation; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D011509:Proteoglycans / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction
D055513:Connective Tissue Growth Factor; D017868:Cyclic AMP-Dependent Protein Kinases; D004247:DNA; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D011509:Proteoglycans; C526317:CCN2 protein, human