title: EBP50 inhibits the anti-mitogenic action of the parathyroid hormone type 1 receptor in vascular smooth muscle cells.
abstract: Parathyroid hormone-related protein (PTHrP) and the parathyroid hormone type 1 receptor (PTH1R) are important regulators of vascular remodeling. PTHrP expression is associated to increased proliferation of vascular smooth muscle cells (VSMC). In contrast, signaling via the PTH1R inhibits cell growth. The mechanisms regulating the dual effect of PTHrP and PTH1R on VSMC proliferation are only partially understood. In this study we examined the role of the adaptor protein ezrin-radixin-moesin-binding phosphoprotein (EBP50) on PTH1R expression, trafficking, signaling and control of A10 cell proliferation. In normal rat vascular tissues, EBP50 was restricted to the endothelium with little expression in VSMC. EBP50 expression significantly increased in VSMC following angioplasty in parallel with PTHrP. Interestingly, PTHrP was able to induce EBP50 expression. In the clonal rat aortic smooth muscle cell line A10, EBP50 increased the recruitment of PTH1R to the cell membrane and delayed its internalization in response to PTHrP(1-36). This effect required an intact C-terminal motif in the PTH1R. In naïve A10 cells, PTHrP(1-36) stimulated cAMP production but not intracellular calcium release. In contrast, PTHrP(1-36) induced both cAMP and calcium signaling in A10 cells over-expressing EBP50. Finally, EBP50 attenuated the induction of p27(kip1) and the anti-proliferative effect of PTHrP(1-36). In summary, this study demonstrates the dynamic expression of EBP50 in vessels following injury and the effects of EBP50 on PTH1R function in VSMC. These findings highlight one of the mechanisms leading to increased VSMC proliferation and have important implication in the understanding of the molecular events leading to restenosis.
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA.
authors.forename: Gyun Jee
authors.initials: GJ
authors.lastname: Song
authors.forename: Stacey
authors.initials: S
authors.lastname: Barrick
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Leslie
authors.forename: Brian
authors.initials: B
authors.lastname: Sicari
authors.forename: Nathalie M
authors.initials: NM
authors.lastname: Fiaschi-Taesch
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bisello
mesh_terms: D017130:Angioplasty; D000818:Animals; D002339:Carotid Arteries / Q000378:metabolism / Q000601:surgery; D002352:Carrier Proteins / Q000378:metabolism*; D049109:Cell Proliferation; D004705:Endocytosis; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008934:Mitogens / Q000378:metabolism*; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D058426:Neointima / Q000378:metabolism / Q000473:pathology; D010750:Phosphoproteins / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers; D015854:Up-Regulation
chemical_list: D002352:Carrier Proteins; D008934:Mitogens; D010750:Phosphoproteins; D044168:Receptor, Parathyroid Hormone, Type 1; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor