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β‐Estradiol results in a proprotein convertase subtilisin/kexin type 9‐dependent increase in low‐density lipoprotein receptor levels in human hepatic HuH7 cells
Author(s) -
Starr Amanda E.,
Lemieux Valérie,
Noad Jenny,
Moore Jasmine I.,
Dewpura Thilina,
Raymond Angela,
Chrétien Michel,
Figeys Daniel,
Mayne Janice
Publication year - 2015
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13309
Subject(s) - pcsk9 , ldl receptor , downregulation and upregulation , kexin , endocrinology , medicine , proprotein convertase , low density lipoprotein , lipoprotein , chemistry , biology , cholesterol , biochemistry , gene
The lower risk of coronary artery disease in premenopausal women than in men and postmenopausal women implicates sex steroids in cardioprotective processes. β‐Estradiol upregulates liver low‐density lipoprotein receptor ( LDLR ), which, in turn, decreases circulating levels of low‐density lipoprotein, which is a risk factor for coronary artery disease. Conversely, LDLR protein is negatively regulated by proprotein convertase subtilisin/kexin type 9 ( PCSK 9). Herein, we investigated PCSK 9 regulation by β‐estradiol and its impact on LDLR in human hepatocarcinoma HuH7 cells grown in the presence or absence of β‐estradiol. Immunoblot analysis showed upregulation of LDLR at 3 μ m β‐estradiol (140%), and the upregulation reached 220% at 10 μ m β‐estradiol; only at the latter dose was an increase in LDLR mRNA detected by qPCR , suggesting post‐translational regulation of LDLR . No changes in PCSK 9 mRNA or secreted protein levels were detected by qPCR or ELISA , respectively. β‐estradiol‐conditioned medium devoid of PCSK 9 failed to upregulate LDLR . Similarly, PCSK 9 knockdown cells showed no upregulation of LDLR by β‐estradiol. Together, these results indicate a requirement for PCSK 9 in the β‐estradiol‐induced upregulation of LDLR . A radiolabeling assay showed a significant, dose‐dependent decrease in the ratio of secreted phospho PCSK 9 to total secreted PCSK 9 with increasing β‐estradiol levels, suggesting a change in the functional state of PCSK 9 in the presence of β‐estradiol. Our results indicate that the protein upregulation of LDLR at subtranscriptionally effective doses of β‐estradiol, and its supratranscriptional upregulation at 10 μ m β‐estradiol, occur through an extracellular PCSK 9‐dependent mechanism.