Y-box protein 1 stimulates mesangial cell proliferation via activation of ERK1/2.
OBJECTIVE
To investigate the effects of Y-box protein 1 (YB-1) on the mitogen-activated protein kinase pathway to ascertain which signaling pathway is involved in YB-1-induced mesangial cell (MC) proliferation.


METHODS
The rat MC line HBZY-1 was transfected with pcDNA3.1-YB-1. Cell proliferation was determined by [(3)H]thymidine incorporation, cell counting and cell-cycle analysis. The expression of cyclins was examined by real-time RT-PCR and immunoblotting analysis. Phosphorylation of c-Raf, MEK1/2, and ERK1/2 was detected by immunoblotting analysis.


RESULTS
MCs transfected with YB-1 showed an increased DNA synthesis and number of cells in the S and G2 phases of the cell cycle. The expression of cyclins (cyclin A2, cyclin D1, cyclin E and p27) was increased, while p21 levels were decreased. The expression levels of phosphorylated c-Raf kinase, MEK1/2 and the ERK1/2 proteins were elevated in MCs transfected with YB-1. YB-1-stimulated cell proliferation was blocked by U0126, a specific inhibitor of ERK1/2. ERK1/2 regulated YB-1 expression in MCs stimulated with TGF-beta, an effect that was inhibited by U0126.


CONCLUSIONS
YB-1 has an apparent stimulatory effect on c-Raf, MEK1/2, ERK1/2 and cell-cycle progression in MCs, after which activated ERK1/2 goes on to upregulate YB-1 expression and augment the proliferative effect of YB-1.
Feng
Quancheng
Q
Department of Nephrology, Nanjing Children's Hospital, Nanjing Medical University, Nanjing 210008, PR China.
Huang
Songming
S
Zhang
Aihua
A
Chen
Qiuxia
Q
Guo
Xirong
X
Chen
Ronghua
R
Yang
Tianxin
T
D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000096:biosynthesis; D019927:Cyclin E / Q000096:biosynthesis; D050527:Mesangial Cells / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D051840:Y-Box-Binding Protein 1 / Q000502:physiology*
D019927:Cyclin E; D051840:Y-Box-Binding Protein 1; D019938:Cyclin D1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3