Mechanistic implications for LDL receptor degradation from the PCSK9/LDLR structure at neutral pH.
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ABSTRACT:
SUBMITTER: Lo Surdo P
PROVIDER: S-EPMC3245695 | biostudies-literature | 2011 Dec
REPOSITORIES: biostudies-literature
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Mechanistic implications for LDL receptor degradation from the PCSK9/LDLR structure at neutral pH.
Lo Surdo Paola P Bottomley Matthew J MJ Calzetta Alessandra A Settembre Ethan C EC Cirillo Agostino A Pandit Shilpa S Ni Yan G YG Hubbard Brian B Sitlani Ayesha A Carfí Andrea A
EMBO reports 20111201 12
The protein PCSK9 (proprotein convertase subtilisin/kexin type 9) is a key regulator of low-density lipoprotein receptor (LDLR) levels and cardiovascular health. We have determined the crystal structure of LDLR bound to PCSK9 at neutral pH. The structure shows LDLR in a new extended conformation. The PCSK9 C-terminal domain is solvent exposed, enabling cofactor binding, whereas the catalytic domain and prodomain interact with LDLR epidermal growth factor(A) and β-propeller domains, respectively. ...[more]
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Project description:PCSK9 (proprotein convertase subtilisin/kexin 9) is a secreted serine protease that regulates cholesterol homoeostasis by inducing post-translational degradation of hepatic LDL-R [LDL (low-density lipoprotein) receptor]. Intramolecular autocatalytic processing of the PCSK9 zymogen in the endoplasmic reticulum results in a tightly associated complex between the prodomain and the catalytic domain. Although the autocatalytic processing event is required for proper secretion of PCSK9, the requirement of proteolytic activity in the regulation of LDL-R is currently unknown. Co-expression of the prodomain and the catalytic domain in trans allowed for production of a catalytically inactive secreted form of PCSK9. This catalytically inactive PCSK9 was characterized and shown to be functionally equivalent to the wild-type protein in lowering cellular LDL uptake and LDL-R levels. These findings suggest that, apart from autocatalytic processing, the protease activity of PCSK9 is not necessary for LDL-R regulation.
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| S-EPMC4900664 | biostudies-literature
Project description:Proprotein convertase subtilisin/kexin type 9 (PCSK9) posttranslationally regulates hepatic low-density lipoprotein receptors (LDLRs) by binding to LDLRs on the cell surface, leading to their degradation. The binding site of PCSK9 has been localized to the epidermal growth factor-like repeat A (EGF-A) domain of the LDLR. Here, we describe the crystal structure of a complex between PCSK9 and the EGF-A domain of the LDLR. The binding site for the LDLR EGF-A domain resides on the surface of PCSK9's subtilisin-like catalytic domain containing Asp-374, a residue for which a gain-of-function mutation (Asp-374-Tyr) increases the affinity of PCSK9 toward LDLR and increases plasma LDL-cholesterol (LDL-C) levels in humans. The binding surface on PCSK9 is distant from its catalytic site, and the EGF-A domain makes no contact with either the C-terminal domain or the prodomain. Point mutations in PCSK9 that altered key residues contributing to EGF-A binding (Arg-194 and Phe-379) greatly diminished binding to the LDLR's extracellular domain. The structure of PCSK9 in complex with the LDLR EGF-A domain defines potential therapeutic target sites for blocking agents that could interfere with this interaction in vivo, thereby increasing LDLR function and reducing plasma LDL-C levels.
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Project description:BACKGROUND:Green tea drinking has been proven to lower lipid and exert cardiovascular protection, while the potential mechanism has not been fully determined. This study was to investigate whether the beneficial impact of epigallocatechingallate (EGCG), a type of catechin in green tea on lipids is associated with proprotein convertase subtilisin/kexin type 9 (PCSK9) pathways. METHODS:We studied the effects and underlying molecular mechanism of EGCG or green tea on regulating cholesterol from human, animal and in vitro. RESULTS:In the age- and gender-matched case control observation, we found that individuals with frequent tea consumption (n?=?224) had the lower plasma PCSK9 and low density lipoprotein cholesterol (LDL-C) levels compared with ones without tea consumption (n?=?224, p?<?0.05). In the high fat diet (HFD) fed rats, EGCG administration significantly lowered circulating PCSK9 concentration and liver PCSK9 expression, along with up-regulated LDL receptor (LDLR) expression but decreased level of LDL-C. In hepatic cell study, similar results were obtained regarding the impact of EGCG on LDLR and PCSK9 expression. The assay transposase-accessible chromatic with high-throughput sequencing (ATAC-seq) and subsequent results suggested that two transcription factors, hepatocyte nuclear factor-1? (HNF-1?) and forkhead box class O (FoxO) 3a involved in inhibitory action of EGCG on PCSK9 expression. CONCLUSIONS:The present study demonstrates that EGCG suppresses PCSK9 production by promoting nuclear FoxO3a, and reducing nuclear HNF1?, resulting in up-regulated LDLR expression and LDL uptake in hepatocytes. Thereby inhibiting liver and circulating PCSK9 levels, and ultimately lowering LDL-C levels.
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