Protein kinase C-dependent upregulation of N-cadherin expression by phorbol ester in human calvaria osteoblasts.
Cell-cell adhesion mediated by cadherins is believed to play an essential role in the control of cell differentiation and tissue formation. Our recent studies indicate that N-cadherin is involved in human osteoblast differentiation. However, the signalling molecules that regulate cadherins in osteoblasts are not known. We tested the possibility that N-cadherin expression and function may be regulated by direct activation of protein kinase C (PKC) in human osteoblasts. Treatment of immortalized human neonatal calvaria (IHNC) cells with phorbol 12,13-dibutyrate (100 nM) transiently increased PKC activity. RT-PCR analysis showed that transient treatment with phorbol ester transiently increased N-cadherin mRNA levels at 4-12 h. Western blot analysis showed that N-cadherin protein levels were increased by phorbol ester at 24-48 h, and this was confirmed by immunocytochemical analysis. In contrast, E-cadherin expression was not affected. Transient treatment of IHNC cells with phorbol ester increased cell-cell aggregation, which was suppressed by neutralizing N-cadherin antibody, showing that the increased N-cadherin induced by phorbol ester was functional. Finally, phorbol ester dose-dependently increased alkaline phosphatase activity, an early marker of osteoblast differentiation. This effect was comparable to the promoting effect of BMP-2, a potent activator of osteoblast differentiation. These data show that direct activation of PKC by phorbol ester increases N-cadherin expression and function, and promotes ALP activity in human calvaria osteoblasts, which provides a signaling mechanism by which N-cadherin is regulated and suggests a role for PKC in N-cadherin-mediated control of human osteoblast differentiation.
Delannoy
P
P
INSERM U 349 affiliated CNRS, Lariboisière Hospital, Paris, France.
Lemonnier
J
J
Haÿ
E
E
Modrowski
D
D
Marie
P J
PJ
D000469:Alkaline Phosphatase / Q000187:drug effects / Q000378:metabolism; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D015820:Cadherins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002273:Carcinogens / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology*; D002449:Cell Aggregation / Q000187:drug effects / Q000502:physiology; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002461:Cell Line, Transformed / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007231:Infant, Newborn; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D012886:Skull / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D016212:Transforming Growth Factor beta; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D015820:Cadherins; D002273:Carcinogens; D010703:Phorbol Esters; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D011493:Protein Kinase C; D000469:Alkaline Phosphatase