Expression of parathyroid hormone-related peptide (PTHrP) and PTH/PTHrP receptor in newborn human calvaria osteoblastic cells.
We examined the expression of parathyroid hormone-related peptide (PTHrP) and its receptor in normal newborn human calvaria osteoblastic (NHCO) cells. Northern blot analysis showed that NHCO cells express a single 1.6 kb transcript of PTHrP, which was increased within 1 h (2x) and peaked at 6 h (7x) after serum treatment. In the culture media, the release of PTHrP peptide was maximally increased (4x) 24 h after the addition of serum, as determined by immunoradiometric assay. NHCO cells exhibited a cytoplasmic immunostaining for PTHrP in the presence of serum, and most PTHrP-positive cells were alkaline phosphatase-negative, suggesting that PTHrP was expressed in undifferentiated cells. Furthermore, RT-PCR analysis showed that both PTHrP and PTH/PTHrP receptor were expressed in NHCO cells in basal conditions or after stimulation with serum. The maximal PTHrP expression induced by serum suppressed PTH/PTHrP receptor expression, suggesting that PTHrP down-regulated its receptor in NHCO cells. Treatment with 10 nM human PTH(1-34) which binds to PTH/PTHrP receptors, increased intracellular cAMP levels and alkaline phosphatase activity, and decreased cell growth, indicating that ligand binding to PTH/PTHrP receptors regulates NHCO cell proliferation and differentiation. The expression and synthesis of PTHrP and the presence of functional PTH/PTHrP receptors suggest a possible paracrine mechanism of action of PTHrP in normal human calvaria osteoblastic cells.
Lomri
A
A
INSERM Unit 349, Cell and Molecular Biology of Bone and Cartilage, Lariboisiere Hospital, Paris, France.
de Pollak
C
C
Sebag
M
M
Goltzman
D
D
Kremer
R
R
Marie
P J
PJ
D002478:Cells, Cultured; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007536:Isomerism; D010006:Osteoblasts / Q000378:metabolism*; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism*; D012886:Skull / Q000166:cytology / Q000378:metabolism*
C470121:PTHLH protein, human; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone