The scaffolding protein EBP50 promotes vascular smooth muscle cell proliferation and neointima formation by regulating Skp2 and p21(cip1).
OBJECTIVE
The Ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) is a scaffolding protein known to regulate ion homeostasis in the kidney and intestine. Previous work showed that EBP50 expression increases after balloon injury in rat carotids. This study was designed to determine the role of EBP50 on vascular smooth muscle cells (VSMC) proliferation and the development of neointimal hyperplasia.


RESULTS
Wire injury was performed in wild type (WT) and EBP50 knockout (KO) mice. Two weeks after injury, neointima formation was 80% lower in KO than in WT mice. Proliferation of KO VSMC was significantly lower than WT cells and overexpression of EBP50 increased VSMC proliferation. Akt activity and expression of S-phase kinase protein2 decreased in KO cells resulting in the stabilization of the cyclin-dependent kinase inhibitor, p21(cip1). Consequently, KO cells were arrested in G(0)/G(1) phase. Consistent with these observations, p21(cip1) was detected in injured femoral arteries of KO but not WT mice. No differences in apoptosis between WT and KO were observed.


CONCLUSIONS
EBP50 is critical for neointima formation and induces VSMC proliferation by decreasing S-phase kinase protein2 stability, thereby accelerating the degradation of the cell cycle inhibitor p21(cip1).
Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, 200 Lothrop Street, Pittsburgh, PA 15261, USA.
Gyun Jee
GJ
Song
Stacey
S
Barrick
Kristen L
KL
Leslie
Philip M
PM
Bauer
Veronica
V
Alonso
Peter A
PA
Friedman
Nathalie M
NM
Fiaschi-Taesch
Alessandro
A
Bisello
D000818:Animals; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000502:physiology*; D005263:Femoral Artery / Q000293:injuries / Q000473:pathology / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D032389:Myocytes, Smooth Muscle / Q000166:cytology* / Q000502:physiology*; D058426:Neointima / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D044786:S-Phase Kinase-Associated Proteins / Q000502:physiology*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*
C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D010750:Phosphoproteins; D044786:S-Phase Kinase-Associated Proteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D051057:Proto-Oncogene Proteins c-akt