E₂-BSA activates caveolin-1 via PI₃K/ERK1/2 and lysosomal degradation pathway and contributes to EPC proliferation.
BACKGROUND
The mechanism that estrogen (E(2)) increases the number of endothelial progenitor cells (EPC) is largely unknown. Here we used E(2)-conjugated bovine serum albumin (E(2)-BSA, membrane impermeable) to investigate whether the membrane estrogen receptor (mER) and its related protein caveolin-1 (CAV-1) are involved in these processes.


RESULTS
E(2)-BSA promoted [(3)H]-thymidine incorporation of EPC through increasing CAV-1 expression via mER (ERα, but not ERβ or GPR30). Both cholesterol depletion and CAV-1 knockdown with use of CAV-1 siRNA significantly attenuated E(2)-BSA-induced [(3)H]-thymidine incorporation. Western blot showed that E(2)-BSA increased membrane CAV-1 protein expression 12h after treatment, whereas mRNA levels of CAV-1 were augmented until 24h after E(2)-BSA treatment. Furthermore, pre-incubated EPC with ICI 182780 (a specific ER antagonist), LY 294002 (a selective PI(3)K inhibitor) or PD 98059 (a specific ERK1/2 inhibitor) before E(2)-BSA inhibited the late-stage effect of E(2)-BSA (≥24 h) on up-regulation of CAV-1 mRNA and protein expression. Pulse chase results demonstrated that E(2)-BSA inhibited lysosome-mediated degradation of CAV-1 protein at the early stage (≤12 h), and then resulted in the increased CAV-1 protein.


CONCLUSIONS
In the present work we demonstrated that E(2)-BSA promotes EPC proliferation through mER (ERα) in CAV-1-dependent manner: prolonging the stability of CAV-1 protein through quick inhibition of the lysosomal degradation pathway at the early stage (≤12 h) and up-regulating CAV-1 at transcription levels through PI(3)K/ERK1/2 signaling pathway at the late stage (≥24 h). These data indicated that a there is a novel mechanism of E(2)-BSA in the regulation of EPC proliferation through CAV-1.
Department of Physiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, PR China. tanzhi@mail.sysu.edu.cn
Zhi
Z
Tan
Li-Jun
LJ
Zhou
Yu
Y
Li
Yu-Hong
YH
Cui
Qiu-Ling
QL
Xiang
Gui-Ping
GP
Lin
Ting-Huai
TH
Wang
D000818:Animals; D051242:Caveolin 1 / Q000502:physiology*; D049109:Cell Proliferation; D042783:Endothelial Cells / Q000166:cytology*; D004958:Estradiol / Q000502:physiology*; D005260:Female; D008247:Lysosomes / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012710:Serum Albumin, Bovine / Q000502:physiology*; D013234:Stem Cells
D051242:Caveolin 1; C043090:estradiol-bovine serum albumin; D012710:Serum Albumin, Bovine; D004958:Estradiol; D019869:Phosphatidylinositol 3-Kinases