TY - JOUR
T1 - Transforming growth factor-β1 regulation of resting zone chondrocytes is mediated by two separate but interacting pathways
AU - Sylvia, V. L.
AU - Schwartz, Z.
AU - Dean, D. D.
AU - Boyan, B. D.
N1 - Funding Information:
The authors wish to thank Ms. Sandra Messier for her help in preparing the manuscript and Ms. Monica Luna and Dr. Zhi Chang for their technical assistance. This study was supported by US PHS Grants DE-08603 and DE-05937 and the Center for the Enhancement of the Biology/Biomaterials Interface (CEBBI) at the University of Texas Health Science Center at San Antonio.
PY - 2000/4/17
Y1 - 2000/4/17
N2 - Previous studies have shown that transforming growth factor-β1 (TGF-β1) stimulates protein kinase C (PKC) via a mechanism that is independent of phospholipase C or tyrosine kinase, but involves a pertussis toxin-sensitive G-protein. Maximal activation occurs at 12 h and requires new gene expression. To understand the signaling pathways involved, resting zone chondrocytes were incubated with TGF-β1 and PKC activity was inhibited with chelerythrine, staurosporine or H-7. [35S]Sulfate incorporation was inhibited, indicating that PKC mediates the effects of TGF-β1 on matrix production. However, there was little, if any, effect on TGF-β1-dependent increases in [3H]thymidine incorporation, and TGF-β1-stimulated alkaline phosphatase was unaffected, indicating that these responses to the growth factor are not regulated via PKC. TGF-β1 caused a dose-dependent increase in prostaglandin E2 (PGE2) production which was further increased by PKC inhibition. The increase was regulated by TGF-β1-dependent effects on phospholipase A2 (PLA2). Activation of PLA2 inhibited TGF-β1 effects on PKC, and inhibition of PLA2 activated TGF-β1-dependent PKC. Exogenous arachidonic acid also inhibited TGF-β1-dependent increases in PKC. The effects of TGF-β1 on PKC involve genomic mechanisms, but not regulation of existing membrane-associated enzyme, since no direct effect of the growth factor on plasma membrane or matrix vesicle PKC was observed. These results support the hypothesis that TGF-β1 modulates its effects on matrix production through PKC, but its effects on alkaline phosphatase are mediated by production of PGE2 and protein kinase A (PKA). Inhibition of PKA also decreases TGF-β1-dependent proliferation. We have previously shown that PGE2 stimulates alkaline phosphatase through its EP2 receptor, whereas EP1 signaling causes a decrease in PKC. Thus, there is cross-talk between the two pathways. Copyright (C) 2000 Elsevier Science B.V.
AB - Previous studies have shown that transforming growth factor-β1 (TGF-β1) stimulates protein kinase C (PKC) via a mechanism that is independent of phospholipase C or tyrosine kinase, but involves a pertussis toxin-sensitive G-protein. Maximal activation occurs at 12 h and requires new gene expression. To understand the signaling pathways involved, resting zone chondrocytes were incubated with TGF-β1 and PKC activity was inhibited with chelerythrine, staurosporine or H-7. [35S]Sulfate incorporation was inhibited, indicating that PKC mediates the effects of TGF-β1 on matrix production. However, there was little, if any, effect on TGF-β1-dependent increases in [3H]thymidine incorporation, and TGF-β1-stimulated alkaline phosphatase was unaffected, indicating that these responses to the growth factor are not regulated via PKC. TGF-β1 caused a dose-dependent increase in prostaglandin E2 (PGE2) production which was further increased by PKC inhibition. The increase was regulated by TGF-β1-dependent effects on phospholipase A2 (PLA2). Activation of PLA2 inhibited TGF-β1 effects on PKC, and inhibition of PLA2 activated TGF-β1-dependent PKC. Exogenous arachidonic acid also inhibited TGF-β1-dependent increases in PKC. The effects of TGF-β1 on PKC involve genomic mechanisms, but not regulation of existing membrane-associated enzyme, since no direct effect of the growth factor on plasma membrane or matrix vesicle PKC was observed. These results support the hypothesis that TGF-β1 modulates its effects on matrix production through PKC, but its effects on alkaline phosphatase are mediated by production of PGE2 and protein kinase A (PKA). Inhibition of PKA also decreases TGF-β1-dependent proliferation. We have previously shown that PGE2 stimulates alkaline phosphatase through its EP2 receptor, whereas EP1 signaling causes a decrease in PKC. Thus, there is cross-talk between the two pathways. Copyright (C) 2000 Elsevier Science B.V.
KW - 24,25-(OH)D
KW - Alkaline phosphatase
KW - Chondrocyte culture
KW - Protein kinase C
KW - Signal transduction
KW - Transforming growth factor-β1
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U2 - 10.1016/S0167-4889(00)00030-6
DO - 10.1016/S0167-4889(00)00030-6
M3 - Article
C2 - 10771099
AN - SCOPUS:0034678738
VL - 1496
SP - 311
EP - 324
JO - Biochimica et Biophysica Acta - Molecular Cell Research
JF - Biochimica et Biophysica Acta - Molecular Cell Research
SN - 0167-4889
IS - 2-3
ER -