title: Parathyroid hormone-related protein (107-139) increases human osteoblastic cell survival by activation of vascular endothelial growth factor receptor-2.
abstract: Parathyroid hormone-related protein (PTHrP) (107-139), in contrast to the N-terminal fragment PTHrP (1-36), has been shown to interact with the vascular endothelial growth factor (VEGF) system to modulate human osteoblast differentiation. In this study, we evaluated whether this interaction might affect human osteoblastic cell survival. Pre-incubation with PTHrP (107-139) for 1-24 h dose-dependently (0.1-100 nM) inhibited dexamethasone- or etoposide-induced cell death in human osteoblastic MG-63 cells and human osteoblast-like cells from trabecular bone. This effect, but not that elicited by PTHrP (1-36), was abolished by the VEGF receptor (VEGFR)-2 inhibitors SU5614 and SU1498 or VEGFR-2 siRNA transfection in these cells. PTHrP (107-139), but not PTHrP (1-36), at 100 nM, rapidly (within 2 min) increased VEGFR-2 tyrosine-phosphorylation in MG-63 cells; an effect unaffected by several inhibitors of metalloproteinases, neutralizing VEGF(165) or VEGFR-2 antibodies, or the VEGF binding inhibitor CBO-PP1. The latter two antagonists also failed to affect (125)I-[Tyr(116)] PTHrP (107-115) binding to these cells. Consistent with its effect on VEGFR-2 activation, PTHrP (107-139) rapidly induced extracellular signal-regulated kinase (ERK) 1/2 and Akt activaton, and both ERK and phosphatidylinsositol-3 kinase (PI3K) inhibitors abolished its pro-survival effect in human osteoblastic cells. In addition, SU5614 and the latter two types of inhibitors abrogated Runx2 activation by this peptide in MG-63 cells. Transfection with a dominant-negative Runx2 construct abolished the pro-survival effect of PTHrP (107-139), associated with a decrease in Bcl-2/Bax protein ratio. Our findings demonstrate that PTHrP (107-139) interacts with VEGFR-2 to promote human osteoblastic cell survival by a mechanism involving Runx2 activation.
authors.affiliation: Laboratorio de Metabolismo Mineral y Oseo, Fundación Jiménez Díaz (Capio Group), Madrid, Spain.
authors.forename: Verónica
authors.initials: V
authors.lastname: Alonso
authors.forename: Arancha R
authors.initials: AR
authors.lastname: de Gortázar
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ardura
authors.forename: Irene
authors.initials: I
authors.lastname: Andrade-Zapata
authors.forename: M Victoria
authors.initials: MV
authors.lastname: Alvarez-Arroyo
authors.forename: Pedro
authors.initials: P
authors.lastname: Esbrit
mesh_terms: D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; C493709:RUNX2 protein, human; D042461:Vascular Endothelial Growth Factor A; C079957:parathyroid hormone-related peptide (1-36); C071097:parathyroid hormone-related protein (107-139); D019000:Phosphotyrosine; D005047:Etoposide; D003907:Dexamethasone; D040301:Vascular Endothelial Growth Factor Receptor-2; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases