Parathyroid hormone-related peptide stimulates osteogenic cell proliferation through protein kinase C activation of the Ras/mitogen-activated protein kinase signaling pathway.
We investigated the mechanisms of parathyroid hormone-related peptide (PTHrP)-mediated effects on osteogenic cells in primary rat bone marrow cell (BMC) cultures. We first demonstrated by reverse transcriptase-polymerase chain reaction and immunocytochemistry that BMCs express the type I parathyroid hormone/PTHrP receptor. Treatment with PTHrP increased osteogenic cell proliferation as determined by [(3)H]thymidine and bromodeoxyuridine incorporation and augmented osteogenic colonies. Immunocytochemistry and Western blotting revealed no direct effect on expression of the osteoblast markers, type I collagen, bone sialoprotein, and osteocalcin, indicating that PTHrP did not directly stimulate differentiation in this system. PTHrP increased mitogen-activated protein kinase (MAPK) activity in BMC and MAPK activity, and PTHrP-induced osteogenic cell proliferation could be blocked by the MEK inhibitor PD-098059. PTHrP also increased Ras activity in BMC. Although wortmannin and H8, inhibitors of phosphoinositol 3-kinase and protein kinase A, respectively, did not block PTHrP-stimulated Ras or MAPK activity, chelerythrin chloride, a known protein kinase C inhibitor, did block these PTHrP actions as well as PTHrP-induced osteogenic cell proliferation. These results demonstrate that PTHrP stimulates osteogenic cell proliferation in rat marrow mesenchymal progenitor cells through protein kinase C-dependent activation of the Ras and MAPK signaling pathway.
Miao
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D
Calcium Research Laboratory, Department of Medicine, McGill University Health Centre and McGill University, Montreal, Quebec H3A 1A1, Canada.
Tong
X K
XK
Chan
G K
GK
Panda
D
D
McPherson
P S
PS
Goltzman
D
D
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D002113:Calcification, Physiologic; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System; D008297:Male; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments / Q000494:pharmacology*; D010641:Phenotype; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018631:ras Proteins / Q000378:metabolism*
D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D011506:Proteins; C054296:parathyroid hormone-related protein (1-34); D011493:Protein Kinase C; D000469:Alkaline Phosphatase; D018631:ras Proteins