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17β-Estradiol Inhibits PCSK9-Mediated LDLR Degradation Through GPER/PLC Activation in HepG2 Cells
Wei Fu1, Xiao-Ping Gao2, Sheng Zhang1
1Department of Physiology, West China School of Basic Medical and Forensic Medicine, Sichuan University, Chengdu, China.
Abstract:
Plasma levels of PCSK9 are significantly higher in postmenopausal women. Pharmacologically increased estrogen levels have been shown to lower PCSK9 and LDL-C levels in animals and humans. The action of estrogen suggests that it has the ability to prevent PCSK9-mediated LDLR degradation in liver cells. However, little is known about how estrogen alters PCSK9-mediated LDLR degradation. Here, we report that 17β-estradiol (βE2) reduces PCSK9-mediated LDLR degradation by a mechanism that involves activation of the G protein-coupled estrogen receptor (GPER). In cultured HepG2 cells, βE2 prevented the internalization of PCSK9, which subsequently lead to PCSK9-mediated LDLR degradation. The altered LDLR levels also resulted in an increase in LDL uptake that was not observed in the absence of PCSK9. In addition, we showed that clathrin was rapidly increased in the presence of PCSK9, and this increase was blocked by βE2 incubation, suggesting rapid recruitment of clathrin in HepG2 cells. PLCγ activation and intracellular Ca2+ release were both increased due to the rapid effect of estrogen. By using a GPER antagonist G15, we demonstrated that the GPER mediates the action of estrogen. Together, the data from this in vitro study demonstrate that estrogen can regulate LDLR levels mainly through GPER activation, which prevents PCSK9-dependent LDLR degradation in HepG2 cells.
Insights
Estrogen, specifically 17β-estradiol, reduces the degradation of LDL receptors by PCSK9 in liver cells. This effect is mediated by the G protein-coupled estrogen receptor (GPER), potentially impacting cholesterol levels.
Area of Science:
- Biochemistry
- Endocrinology
- Cell Biology
Background:
- Plasma levels of PCSK9 are elevated in postmenopausal women.
- Estrogen administration lowers PCSK9 and LDL-C, suggesting a protective role against PCSK9-mediated low-density lipoprotein receptor (LDLR) degradation.
Purpose of the Study:
- To elucidate the mechanism by which estrogen regulates PCSK9-mediated LDLR degradation.
- To investigate the role of the G protein-coupled estrogen receptor (GPER) in this process.
Main Methods:
- Utilized cultured HepG2 cells to study the effects of 17β-estradiol (βE2) on PCSK9 and LDLR interactions.
- Employed GPER antagonist G15 to confirm the receptor's involvement.
- Monitored PCSK9 internalization, LDLR levels, LDL uptake, clathrin recruitment, PLCγ activation, and intracellular Ca2+ release.
Main Results:
- βE2 inhibited PCSK9 internalization and subsequent LDLR degradation in HepG2 cells.
- This inhibition led to increased LDL uptake, dependent on PCSK9 presence.
- βE2 blocked PCSK9-induced clathrin recruitment and enhanced PLCγ activation and Ca2+ release, indicating rapid signaling via GPER.
Conclusions:
- Estrogen (βE2) prevents PCSK9-dependent LDLR degradation through GPER activation.
- GPER activation by estrogen influences intracellular signaling pathways, including clathrin-mediated endocytosis.
- Estrogen's regulation of LDLR levels via GPER offers a potential therapeutic target for managing cholesterol metabolism.
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