Role Of PCSK9 Research Articles

Insights into PCSK9-LDLR Regulation and Trafficking via the Differential Functions of MHC-I Proteins HFE and HLA-C.

PCSK9 is implicated in familial hypercholesterolemia via targeting the cell surface PCSK9-LDLR complex toward lysosomal degradation. The M2 repeat in the PCSK9's C-terminal domain is essential for its extracellular function, potentially through its interaction with an unidentified "protein X". The M2 repeat was recently shown to bind an R-x-E motif in MHC-class-I proteins (implicated in the immune system), like HLA-C, and causing their lysosomal degradation. These findings suggested a new role of PCSK9 in the immune system and that HLA-like proteins could be "protein X" candidates. However, the participation of each member of the MHC-I protein family in this process and their regulation of PCSK9's function have yet to be determined. Herein, we compared the implication of MHC-I-like proteins such as HFE (involved in iron homeostasis) and HLA-C on the extracellular function of PCSK9. Our data revealed that the M2 domain regulates the intracellular sorting of the PCSK9-LDLR complex to lysosomes, and that HFE is a new target of PCSK9 that inhibits its activity on the LDLR, whereas HLA-C enhances its function. This work suggests the potential modulation of PCSK9's functions through interactions of HFE and HLA-C.

The role of PCSK9 in metabolic dysfunction-associated steatotic liver disease and its impact on bariatric surgery outcomes

BackgroundMetabolic dysfunction-associated steatotic liver disease (MASLD) is closely tied to obesity. The degree ranges from steatosis (MASL) and steatohepatitis (MASH) to liver cirrhosis. PCSK9 controls cholesterol and lipid particle transport to the liver. PCSK9 might interfere with the pathophysiology of MASLD and bariatric surgery (BS) outcomes of patients with MASLD. ObjectivesEvaluate the relationship between serum and hepatic PCSK9 levels with the degree of MASLD and the metabolic outcome of BS. SettingUniversity Hospital, Spain. MethodsA total of 110 patients with obesity undergoing BS were classified according to liver histology as controls, MAS, and MASH. PCSK9 levels in serum were measured before and 6 months after BS using enzyme-linked immunosorbent assay. PCSK9 protein and mRNA levels in liver tissue were analyzed by immunohistochemistry and reverse transcriptase-polymerase chain reaction, respectively. ResultsHepatic PCSK9 protein levels were diminished in MASL and MASH compared with patients without MASLD and showed a strong negative association with MASLD severity scores. Liver PCSK9 mRNA was higher in MASH compared with controls and MASL and showed positive associations with MASLD severity scores. There were no differences in serum PCSK9 pre or postBS between the groups. Pre- and postsurgery serum PCSK9 positively correlated with cholesterol fold-changes and body mass index (BMI), cholesterol, and low-density lipoprotein -cholesterol fold-changes, respectively. PCSK9 fold-change positively correlated with BMI changes and was the sole variable explaining BMI fold changes in a regression model. ConclusionsPCSK9 mRNA and protein in the liver might be associated with the degree of MASLD. Serum PCSK9 may be associated with cholesterol and/or BMI fold changes. Serum changes of PCSK9 after BS could explain BMI loss outcome.

Protective effect of alirocumab, a PCSK9 inhibitor, on the sciatic nerve of rats with diabetic peripheral neuropathy.

Dyslipidemia has been considered a risk factor for diabetic peripheral neuropathy. Proprotein convertase subtilisin-like/Kexin 9 inhibitor (PCSK9) inhibitors are a new type of lipid-lowering drug currently in clinical use. The role of PCSK9 in diabetic peripheral neuropathy is still unclear. In this study, the effect of alirocumab, a PCSK9 inhibitor, on the sciatic nerve in rats with diabetic peripheral neuropathy and its underlying mechanisms were investigated. The diabetic peripheral neuropathy rat model was established by using a high-fat diet combined with streptozotocin injection, and experimental subjects were divided into normal, diabetic peripheral neuropathy, and alirocumab groups. The results showed that Alirocumab improved nerve conduction, morphological changes, and small fiber deficits in rats with DPN, possibly related to its amelioration of oxidative stress and the inflammatory response.

FRI091 Treatment Of Secondary Hyperlipidemia Due To Nephrotic Syndrome

Abstract Disclosure: J. Girard: None. H. Quadri: None. B. Jiang: None. B.K. Force: None. L. Abushamat: None. R.S. Aguirre: None. Introduction: Secondary Hyperlipidemia associated with nephrotic syndrome contributes to significant cardiovascular morbidity. The elevated atherogenic lipoprotein levels are caused by upregulation of HMG-CoA reductase and downregulation of lipoprotein lipase. More recently, studies in mice have linked PCSK9 and Inducible Degrader of the LDL Receptor (IDOL) as primary contributors to hypercholesterolemia in nephrotic syndrome due to the decrease in LDL receptor recycling (1). Treating nephrotic syndrome is the first-line treatment for the associated secondary hyperlipidemia. Since exposure time to atherogenic lipoproteins matters in the development of cardiovascular disease, statins, with or without ezetimibe, are utilized. PCSK9 inhibitors are initiated if LDL remains elevated despite these measures. This case report highlights a severe case of hypercholesterolemia associated with nephrotic syndrome and treatment response. Clinical Case: A 55-year-old male with no significant past medical history presented to the emergency department with shortness of breath and lower extremity edema. He denied a family and personal history of premature cardiovascular disease. Initial evaluation revealed a serum total cholesterol on 10x dilution of 833.9 (</=200mg/dL), calculated LDL 718mg/dL (<100mg/dL), triglycerides 381mg/dL (<150mg/dL), HDL 39.3mg/dL (40-60mg/dL), Apo B >400mg/dL (<90mg/dL), and Lp(a) 17.5mg/dL (<75mg/dL). His serum albumin was <1.5g/dL (4.2-4.5g/dL), creatinine 2mg/dL (0.7-1.3mg/dL), and 24-hour calculated urinary protein level 10,294mg/24-hour (30-150mg/24-hour). A kidney biopsy revealed a mixed Type III and Type V Lupus Nephritis. The patient started lupus treatment along with atorvastatin 80mg qHS, fenofibrate 45mg daily, and ezetimibe 10mg daily. His LDL decreased to 418mg/dL (<100mg/dL) after 15 days. The patient continued to have undetectable albumin although kidney function improved after 2 months. We planned to initiate PCSK9 inhibitor treatment for further LDL reduction pending treatment of lupus, but patient died from septic shock prior to initiation. Conclusion: This case illustrates that extremely elevated LDL levels from nephrotic syndrome resulted in a nearly 60% reduction of LDL with statin and ezetimibe treatment. Statins, ezetimibe and PCSK9 inhibitor therapy should be considered stepwise when treating secondary hyperlipidemia from nephrotic syndrome. 1. LIU S, VAZIRI ND. ROLE OF PCSK9 AND IDOL IN THE PATHOGENESIS OF ACQUIRED LDL RECEPTOR DEFICIENCY AND HYPERCHOLESTEROLEMIA IN NEPHROTIC SYNDROME. NEPHROL DIAL TRANSPLANT. 2014 MAR;29(3):538-43. DOI: 10.1093/NDT/GFT439. EPUB 2013 OCT 28. PMID: 24166456 Presentation: Friday, June 16, 2023

Proprotein Convertase Subtilisin/Kexin 9 as a Modifier of Lipid Metabolism in Atherosclerosis.

Despite being the most common treatment strategy in the management of atherosclerosis and subsequent cardiovascular disease, classical statin therapy has certain disadvantages, including numerous side effects. In addition, a regimen with daily administration of the drug is hard to comply with. Thus, there is a need for modern and more efficient therapeutic strategies in CVD treatment. There is extensive evidence indicating that PCSK9 promotes atherogenesis through a variety of mechanisms. Thus, new treatment methods can be developed that prevent or alleviate atherosclerotic cardiovascular disease by targeting PCSK9. Comprehensive understanding of its atherogenic properties is a necessary precondition for the establishment of new therapeutic strategies. In this review, we will summarize the available data on the role of PCSK9 in the development and progression of atherosclerosis. In the last section, we will consider existing PCSK9 inhibitors.

Meet the First Authors.

Meet the First Authors.

Abstract 13662: The Role of Pcsk9 in Abdominal Aortic Aneurysm

Introduction: Abdominal aortic aneurysm (AAA) is a local weakening and dilatation of the abdominal aorta ≥50%, is associated with high mortality in the event of rupture and has no current pharmacologic treatment. Proprotein convertase subtilisin/kexin type 9 (Pcsk9), an enzyme mainly known for its production in liver, can cause familial hypercholesterolemia due to gain-of-function mutations. When triggered by pro-inflammatory stimuli, Pcsk9 expression by vascular smooth muscle cells (VSMC) has been found to induce cellular polyploidy, senescence, and apoptosis, hallmarks of AAA. Further, our collaborative consortium identified a relationship between Pcsk9 variants and AAA disease in humans utilizing a genome-wide association stud y (GWAS) in the Million Veteran Program. Lastly, our transcriptional profiling experiments in the porcine pancreatic elastase (PPE) model of murine AAA found significant early (Day 3) upregulation of the Pcsk9 gene in aorta.Monoclonal Pcsk9 antibody therapies are effective for hypercholesterolemic patients who are resistant to conventional statin therapy. However, the role of Pcsk9 in AAA has not been explored in depth. If Pcsk9 were found to be pivotal in disease, Pcsk9-inhibitors could be high priority candidates for investigation in limiting AAA. Methods: Using the PPE model, AAA was induced in wildtype C57Bl/6 mice and Pcsk9 knock-out (KO) mice. Aneurysm growth was monitored via sonography at various time points, and local vascular Pcsk9 and inflammatory marker gene expression were measured by qPCR. In vitro, VSMC were treated with exogenous Pcsk9 and assayed for pro-inflammatory marker expression. Results: Sonographic imaging data showed smaller AAA diameters in Pcsk9 KO mice compared with wildtype C57Bl/6 mice. Inflammatory gene expression was significantly downregulated with Pcsk9 KO. In-vitro VSMCs showed upregulated inflammation after exogenous Pcsk9 treatment. Conclusions: Our data suggest that Pcsk9 plays a crucial role in the development of AAA and could be a viable treatment target to inhibit AAA progression.

PCSK9 regulates the NODAL signaling pathway and cellular proliferation in hiPSCs.

SummaryProprotein convertase subtilisin kexin type 9 (PCSK9) is a key regulator of low-density lipoprotein (LDL) cholesterol metabolism and the target of lipid-lowering drugs. PCSK9 is mainly expressed in hepatocytes. Here, we show that PCSK9 is highly expressed in undifferentiated human induced pluripotent stem cells (hiPSCs). PCSK9 inhibition in hiPSCs with the use of short hairpin RNA (shRNA), CRISPR/cas9-mediated knockout, or endogenous PCSK9 loss-of-function mutation R104C/V114A unveiled its new role as a potential cell cycle regulator through the NODAL signaling pathway. In fact, PCSK9 inhibition leads to a decrease of SMAD2 phosphorylation and hiPSCs proliferation. Conversely, PCSK9 overexpression stimulates hiPSCs proliferation. PCSK9 can interfere with the NODAL pathway by regulating the expression of its endogenous inhibitor DACT2, which is involved in transforming growth factor (TGF) β-R1 lysosomal degradation. Using different PCSK9 constructs, we show that PCSK9 interacts with DACT2 through its Cys-His-rich domain (CHRD) domain. Altogether these data highlight a new role of PCSK9 in cellular proliferation and development.

Evaluating Targeted Therapies in Ovarian Cancer Metabolism: Novel Role for PCSK9 and Second Generation mTOR Inhibitors.

Simple SummaryOvarian cancer (OC) is known for its poor prognosis, due to the absence of reliable biomarkers and its late diagnosis, since the early-stage disease is almost asymptomatic. Lipid metabolism plays an important role in OC progression due to the development of omental metastasis in the abdominal cavity. The aim of our study was to assess the therapeutic role of various enzymes involved in lipid metabolism regulation or synthesis, in different subtypes of OC represented by cell lines as well as patient-derived cancer cell cultures (PDCs). We show that proprotein convertase subtilisin/kexin type 9 (PCSK9), a cholesterol-regulating enzyme, plays a pro-survival role in OC and targeting its expression impairs cancer cell growth. We also tested a small library of metabolic and mTOR-targeting drugs to identify drug vulnerabilities specific to various subtypes of OC. Our results show that in OC cell lines and PDCs the second generation of mTOR inhibitors such as AZD8055, vistusertib, dactolisib and sapanisertib, have higher cytotoxic activity compared to the first generation mTOR inhibitors such as rapalogs. These results suggest that, in the era of precision medicine, it is possible to target the metabolic pathway in OC and identify subtype-specific drug vulnerabilities that could be advanced to the clinic.Background: Dysregulated lipid metabolism is emerging as a hallmark in several malignancies, including ovarian cancer (OC). Specifically, metastatic OC is highly dependent on lipid-rich omentum. We aimed to investigate the therapeutic value of targeting lipid metabolism in OC. For this purpose, we studied the role of PCSK9, a cholesterol-regulating enzyme, in OC cell survival and its downstream signaling. We also investigated the cytotoxic efficacy of a small library of metabolic (n = 11) and mTOR (n = 10) inhibitors using OC cell lines (n = 8) and ex vivo patient-derived cell cultures (PDCs, n = 5) to identify clinically suitable drug vulnerabilities. Targeting PCSK9 expression with siRNA or PCSK9 specific inhibitor (PF-06446846) impaired OC cell survival. In addition, overexpression of PCSK9 induced robust AKT phosphorylation along with increased expression of ERK1/2 and MEK1/2, suggesting a pro-survival role of PCSK9 in OC cells. Moreover, our drug testing revealed marked differences in cytotoxic responses to drugs targeting metabolic pathways of high-grade serous ovarian cancer (HGSOC) and low-grade serous ovarian cancer (LGSOC) PDCs. Our results show that targeting PCSK9 expression could impair OC cell survival, which warrants further investigation to address the dependency of this cancer on lipogenesis and omental metastasis. Moreover, the differences in metabolic gene expression and drug responses of OC PDCs indicate the existence of a metabolic heterogeneity within OC subtypes, which should be further explored for therapeutic improvements.

Role of Pcsk9 In The Diagnosis Thyroid Disorder in Patient Women

This study for the diagnosis of thyroid using pcsk9.The current study was conducted on seventy women patients suffering from thyroid disease attending in Center for diabetes and Endocrinology Unit in each of Al-Sadder Teaching Hospital and AL FURAT AL AWSAT Hospital in Al-Najaf province/ Iraq, and during the period from September until December 2017. The sample patients were divided into four study groups: premenopausal hypothyroidism patients group (20), postmenopausal hypothyroidism (15), premenopausal hyperthyroidism patients groups (17), and postmenopausal hyperthyroidism (18). The control group composed of 18 healthy women, also divided into premenopausal control and postmenopausal control. The results indicated a significant increase (p<0.05) in pcsk9 in hypothyroidism patients compared with the control group, while a significant decrease (p<0.05) in pcsk9 in hyperthyroidism patients compared with the control group. The results indicated a significant decrease (p<0.05) in pcsk9 in premenopausal hyperthyroidism patients compared with the control group, and a significant decrease (p<0.05) in pcsk9 in postmenopausal hyperthyroidism patients compared with the control group. The results indicated a significant increase (p<0.05) in pcsk9 in premenopausal hypothyroidism patients compared with the control group, and a significant increase (p<0.05) in pcsk9 in the postmenopausal hypothyroidism patients compared with the control group, also a significant increase in pcsk9 in postmenopausal than premenopausal.

The role of PCSK9 in the regulation of lipoprotein transport (review)

The role of PCSK9 in the regulation of lipoprotein transport (review)

On the role of PCSK9 in the development of atherosclerosis: molecular aspects

On the role of PCSK9 in the development of atherosclerosis: molecular aspects

PCSK9 regulates pyroptosis via mtDNA damage in chronic myocardial ischemia.

Proprotein convertase subtilisin/Kexin type 9 (PCSK9) and pyroptosis both play important roles in myocardial infarction. This study was designed to test the hypothesis that PCSK9 regulates pyroptosis in cardiomyocytes during chronic myocardial ischemia. Primary cardiomyocytes were isolated from WT and PCSK9-/- mice. HL-1 cardiomyocytes were used to set up PCSK9-deficient (PCSK9-/-) and PCSK9-upregulated (PCSK9CRISPRa) cardiomyocyte cell line with CRISPR/Cas9 knockout or activation plasmid. Additional studies were performed with chronic myocardial ischemia in WT and PCSK9-/- mice. We observed that PCSK9 initiates mitochondrial DNA (mtDNA) damage, activates NLRP3 inflammasome signaling (NLRP3, ASC, Caspase-1, IL-1β, and IL-18), and subsequently induces Caspase-1-dependent pyroptosis. There was an intense expression of PCSK9 and pyroptosis marker, GSDMD-NT, in the zone bordering the infarct area. PCSK9-/- significantly suppressed expression of NLRP3 inflammasome signaling, GSDMD-NT, and LDH release. Furthermore, serum levels of PCSK9, NLPR3 inflammasome signaling, and pyroptosis (GSDMD and LDH release) were significantly elevated in patients with chronic myocardial ischemia as compared to those in age-matched healthy subjects. Human hearts with recent infarcts also showed high expression of PCSK9 and GSDMD-NT in the border zone similar to that in the infarcted mouse heart. These observations provide compelling evidence for the role ofPCSK9 in regulating Caspase-1-dependent pyroptosis via mtDNA damage and may qualify pro-inflammatory cytokines and pyroptosis as potential targets to treat PCSK9-related cardiovascular diseases.

Key aspects of PCSK9 inhibition beyond LDL lowering.

Our primary objective is to review the most recent findings on the biology of PCSK9 and on two key aspects of PCSK9 inhibition beyond LDL control of great clinical relevance: the regulation of lipoprotein (a) circulating levels by PCSK9 inhibitors and the putative diabetogenic effects of these novel therapies. The reality of two distinct extracellular and intracellular pathways by which PCSK9 decreases the abundance of the LDLR at the surface of many cell types, most importantly hepatocytes, has recently been established. In contrast, the exact mechanisms by which PCSK9 inhibitors lower the circulating levels of lipoprotein (a) remain a point of major dispute. Despite strong indications from genetic studies that PCSK9 inhibition should increase diabetes risk, no such effect has been observed in clinical trials, and in-vitro and in-vivo studies do not clarify this issue. The trafficking pathways by which PCSK9 enhance LDLR degradation via the endolysosomal extracellular route or via the Golgi-lysosomal intracellular route remain to be fully elucidated. The mechanisms by which PCSK9 inhibitors reduce lipoprotein (a) also merit additional research efforts. The role of PCSK9 on glucose metabolism should likewise be studied in depth.

The ever-expanding saga of the proprotein convertases and their roles in body homeostasis: emphasis on novel proprotein convertase subtilisin kexin number 9 functions and regulation.

The nine members of the proprotein convertase family play major physiological roles during development and in the adult, and their dysregulation leads to various diseases. The primary objective of this article is to review recent findings on the clinical importance of some of these convertases concentrating mostly on PCSK9, the ninth member of the convertase family. This includes the transcriptional and translational regulation of PCSK9, its ability to enhance the degradation of LDL receptor (LDLR), and the implication of PCSK9 in inflammation and sepsis. PCSK9 levels are upregulated by E2F1 and reduced by specific miRNAs and by Annexin A2 that bind the 3' end of its mRNA. The implication of the LDLR in the clearance of pathogenic bacterial debris in mice and human puts in perspective a new role for PCSK9 in the regulation of sepsis. The specific implication of the LDLR in the clearance of Lp(a) is now confirmed by multiple studies of PCSK9 inhibition in human cohorts. Emerging data suggest that PCSK9 can be regulated at the transcriptional and translational levels by specific factors and miRNAs. The identification of a novel pocket in the catalytic domain of PCSK9 represents a harbinger for a new class of small inhibitor drugs. The implication of the LDLR in reducing the effects of bacterially induced sepsis has been supported by both human and mouse data. Outcome studies confirmed the clinical importance of reducing PCSK9 levels. The present review puts in perspective new developments in the PCSK9 biology and its regulation of the LDLR. VIDEO ABSTRACT: http://links.lww.com/COL/A17.

PCSK9 Concentrations in Cerebrospinal Fluid Are Not Specifically Increased in Alzheimer’s Disease

The role of PCSK9 in Alzheimer's disease (AD) is controversial. We compared cerebrospinal fluid (CSF) PCSK9 concentrations in 36 AD and 31 non-AD patients. CSF PCSK9 levels did not differ between AD and non-AD groups (2.80 versus 2.62 ng/mL). However, PCSK9 CSF levels were increased in AD and non-AD patients with other neurodegenerative process (non-AD ND, n = 20) compared to patients without neurodegenerative disorders (non-ND, n = 11): 2.80 versus 2.30 (p < 0.005) and 2.83 versus 2.30 ng/mL (p = NS), respectively. CSF PCSK9 were positively correlated with AD biomarkers (Aβ1-42, T-tau, and P-tau). PCSK9 concentrations in CSF are increased in neurodegenerative disorders rather than specifically in AD.

Pleiotropic Anti-atherosclerotic Effects of PCSK9 InhibitorsFrom Molecular Biology to Clinical Translation.

Clinical trials with PCSK9 inhibitors have shown a robust decrease in plasma LDL levels and a significant reduction in the incidence of cardiovascular atherosclerotic events. However, the role of PCSK9 in atherosclerosis is not well investigated and it remains unclear whether PCSK9 inhibition has direct, LDL-independent, anti-atherosclerotic effects. This review outlines the molecular pathways and targets of PCSK9 in atherosclerosis and summarizes the experimental and clinical data supporting the anti-atherosclerotic (pleiotropic) actions of PCSK9 inhibitors. PCSK9 is expressed by various cell types that are involved in atherosclerosis (e.g., endothelial cell, smooth muscle cell, and macrophage) and is detected inside human atherosclerotic plaque. Preclinical studies have shown that inhibition of PCSK9 can attenuate atherogenesis and plaque inflammation. Besides increasing plasma LDL, PCSK9 appears to promote the initiation and progression of atherosclerosis. Inhibition of PCSK9 may confer atheroprotection that extends beyond its lipid-lowering effects.

A new role for PCSK9 as a co-activator of platelet reactivity

A new role for PCSK9 as a co-activator of platelet reactivity

The anti-adipogenic effect of peripheral blood mononuclear cells is absent with PCSK9 loss-of-function variants.

To determine the effect of (1) an oral fat load and (2) pro-protein convertase subtilisin/kexin type (PCSK) 9 loss-of-function (LOF) variant status on the ability of peripheral blood mononuclear cells (PBMC) to inhibit human adipogenesis. PBMC from subjects with one or more PCSK9 LOF variants versus non-variant controls were compared in the fasting state and after an oral fat load. Fasting triglyceride (TG) levels were lower in the LOF variant versus non-variant group but rose to the same level after the oral fat load. Conditioned medium from PBMC was obtained in fasting (PBMC-CM-F) and 4-h postprandial (PBMC-CM-PP) states. PBMC-CM-PP from non-variant controls inhibited adipogenesis of human preadipocytes more than did PBMC-CM-F. In contrast, PBMC-CM-F or -PP from PCSK9 LOF variant subjects had no effect on adipogenesis. After the oral fat load, PBMC from PCSK9 LOF variant subjects showed significant increases in mRNA levels of interleukin-1β, tumor necrosis factor-α, sterol regulatory element binding protein-1c, CD36, and monocyte chemoattractant protein-1 (MCP-1), only MCP-1 mRNA levels increased in PBMC from non-variant controls. The absence of anti-adipogenic action of PBMC from PCSK9 LOF variant subjects points to a novel role for PCSK9 in PBMC-adipose cell interactions.

C-terminal Loop Mutations Determine Folding and Secretion Properties of PCSK9

Human genetics and pharmacologic clinical intervention demonstrate the key role of PCSK9 in cholesterol regulation. To understand the role of the C-terminal domain of PCSK9, two human mutations in this region (S462P and A522T PCSK9) have been profiled. Confirming and extending previous observations, S462P and WT PCSK9 bind to LDLR with equivalent affinity; however, while S462P PCSK9 cleavage is unaffected, its secretion is defective, and association with the ER protein-folding sensor calreticulin, increased. In a similar manner, A522T PCSK9 also exhibits defective secretion and an enhanced association with calreticulin. To assess the in vivo lipid phenotype of the S462P and A522T PCSK9 mutations, Pcsk9-/- mice were infected with AAV8’s encoding the different variants. Although liver transcript levels for all were equivalent, circulating levels of S462P PCSK9, and to a lesser degree A522T PCSK9, were reduced relative to WT PCSK9 correlating with the in vitro phenotype. Further, the extent of reduced circulating S462P or A522T PCSK9 correlated well with increases in mouse liver LDLR and reductions of LDL/ total cholesterol. When interpreted within the context of molecular modeling, it appears that the human non-synonymous polymorphisms S462P and A522T destabilize the C-terminal domain of PCSK9 impacting folding and secretion.