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Expression of protease-activated receptor-2 by osteoblasts
L A Abraham1, C Chinni, A L Jenkins
1School of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia.
Bone
|January 5, 2000
Summary
Osteoblasts express protease-activated receptor-2 (PAR-2), explaining differences in calcium signaling responses to thrombin and PAR-1 peptides. This receptor activation influences intracellular calcium but not osteoblast proliferation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Osteoblasts express protease-activated receptor-1 (PAR-1), activated by thrombin or specific peptides.
- Previous studies noted discrepancies in osteoblast responses to thrombin versus PAR-1-activating peptides, particularly regarding calcium influx and proliferation.
Purpose of the Study:
- To investigate osteoblast expression of protease-activated receptor-2 (PAR-2).
- To determine if PAR-2 expression accounts for observed differences in osteoblast signaling responses.
Main Methods:
- Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry to detect PAR-2 expression in rat and mouse osteoblasts.
- Stimulation of osteoblast-like cells with PAR-2 activators (peptides, trypsin, gingipain-R) and measurement of intracellular calcium ([Ca2+]i).
- Assessment of thymidine incorporation and alkaline phosphatase activity following PAR-2 activation.
Main Results:
- Osteoblasts express PAR-2, confirmed by RT-PCR and immunocytochemistry in rat and mouse models.
- PAR-2 activators (SLIGRL, SLIGKV, trypsin, gingipain-R) induced a dose-dependent increase in intracellular calcium in osteoblast-like cells.
- PAR-2 activation led to calcium influx but did not significantly affect osteoblast proliferation markers (thymidine incorporation, alkaline phosphatase activity).
Conclusions:
- Osteoblasts express functional PAR-2, contributing to calcium signaling pathways.
- PAR-2 activation explains calcium entry discrepancies observed with PAR-1 peptides but not proliferative responses.
- PAR-2 represents a potential target for modulating osteoblast calcium signaling.