Cited by 223Cholesterol and Lipid MetabolismLipoproteins and Cardiovascular HealthLipid metabolism and disorders

The DOI matches its Crossref record; 45 of the 45 references it cites were found in a registry or an index; 23 of the 28 sources its claims cite were checked for support.

Hepatic sortilin regulates both apolipoprotein B secretion and LDL catabolism

Open access

Abstract

Genome-wide association studies (GWAS) have identified a genetic variant at a locus on chromosome 1p13 that is associated with reduced risk of myocardial infarction, reduced plasma levels of LDL cholesterol (LDL-C), and markedly increased expression of the gene sortilin-1 (SORT1) in liver. Sortilin is a lysosomal sorting protein that binds ligands both in the Golgi apparatus and at the plasma membrane and traffics them to the lysosome. We previously reported that increased hepatic sortilin expression in mice reduced plasma LDL-C levels. Here we show that increased hepatic sortilin not only reduced hepatic apolipoprotein B (APOB) secretion, but also increased LDL catabolism, and that both effects were dependent on intact lysosomal targeting. Loss-of-function studies demonstrated that sortilin serves as a bona fide receptor for LDL in vivo in mice. Our data are consistent with a model in which increased hepatic sortilin binds intracellular APOB-containing particles in the Golgi apparatus as well as extracellular LDL at the plasma membrane and traffics them to the lysosome for degradation. We thus provide functional evidence that genetically increased hepatic sortilin expression both reduces hepatic APOB secretion and increases LDL catabolism, providing dual mechanisms for the very strong association between increased hepatic sortilin expression and reduced plasma LDL-C levels in humans.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Increased hepatic sortilin lowers plasma LDL-C by two lysosome-dependent mechanisms: reducing hepatic APOB secretion and increasing LDL catabolism. Sortilin binds LDL with high affinity at neutral pH and releases it at acidic pH, consistent with trafficking LDL to the lysosome.

Key findings

  • Sortilin bound LDL with a Kd of approximately 2 nM at pH 7.4; LDL rapidly dissociated at acidic pH, with kd increasing from 0.004 s⁻¹ at pH 7.4 to 0.380 s⁻¹ at pH 5.0.
  • Increased sortilin reduced APOB secretion by 30% in wild-type mice (P = 0.02) and 50% in Ldlr⁻/⁻ mice (P = 0.01); in primary hepatocytes, the 30% reduction was reversed by E64d (P = 0.0006), and wild-type sortilin reduced APOB secretion by 40% in HuH7 cells, while Sort.Stop and Sort.LAYA did not.
  • Sortilin expression increased LDL catabolism: low- and high-dose sortilin AAV increased LDL fractional catabolic rate by 70% (P = 8 × 10⁻⁵) and 200% (P = 4 × 10⁻⁵), respectively, and increased FCR 3-fold in Ldlr⁻/⁻ mice (P = 2 × 10⁻⁵).
  • Sort1 deficiency reduced LDL FCR by 40% (P = 0.002) versus wild-type and by 50% in Ldlr⁻/⁻;Sort1⁻/⁻ versus Ldlr⁻/⁻ mice (P = 0.02), but sortilin deficiency also reduced APOB secretion by 60% on the APOBEC1⁻/⁻;APOB transgenic background (P = 0.04).

Methods

  • Mouse studies used AAV8-mediated hepatic overexpression of wild-type Sort1 or lysosomal-trafficking mutants (Sort.Stop, Sort.LAYA) in wild-type, Ldlr⁻/⁻, Sort1⁻/⁻, and APOBEC1⁻/⁻;APOB transgenic backgrounds; outcomes included plasma lipids, VLDL-TG and APOB secretion, and ¹²⁵I-LDL turnover.
  • In vitro studies used doxycycline-inducible HuH7 hepatoma cells expressing wild-type sortilin, Sort.Stop, Sort.LAYA, or GFP, with metabolic labeling for APOB secretion, ¹²⁵I-LDL cell association/degradation assays, and immunofluorescence for LDL and LAMP1.
  • Binding was measured by surface plasmon resonance with immobilized soluble human sortilin and LDL across pH 5.0–7.4; statistics used two-tailed Student’s t test and linear regression for VLDL secretion rates, with P < 0.05 considered significant.

Limitations

  • Stated: the basis for reduced APOB/VLDL production in whole-body sortilin-knockout mice remains unknown; the authors suggest possible extrahepatic sortilin effects, developmental compensatory changes, or a parabolic relationship between hepatic sortilin expression and APOB secretion.
  • Stated: the knockout mouse lacks sortilin in all tissues, whereas the human causal variant and the overexpression manipulations were liver-specific, so the knockout phenotype may not reflect selective hepatic sortilin deficiency.
  • Evident from the text: the mechanistic evidence is from mouse and hepatoma-cell models, not direct human intervention; some supporting data are described as “data not shown,” and the human genetic association is cited rather than experimentally tested here.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1172/jci63563

Cites

45 of 45 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

44 Own result · 18 Own interpretation · 13 Partly supported · 5 Supported · 3 No full text of the sources · 2 Own method · 2 No basis given · 1 Supported so far · accuracy not yet measured

Show all 43 claims

  • It may state two separate claims as one. 37
  • Probably not a substantial claim. 10
  • The quote only partly states this claim. 1
45 of 45
  • The paper relies on this without support.

    The association between the chromosome 1p13 locus and reduced LDL-C and myocardial infarction risk is mediated specifically by increased hepatic SORT1 expression rather than by other genes at the locus.

    “harboring several genes including SORT1”
    “markedly increased expression of the gene sortilin-1 (SORT1) in liver”
  • The paper relies on this without support.

    Sortilin functions as a lysosomal trafficking protein.

    “consistent with sortilin's role as a lysosomal trafficking protein.”
  • The paper relies on this without support.

    The SORT1 locus is strongly associated with reduced plasma LDL-C and APOB levels and with protection from coronary heart disease.

    “the very strong association of the SORT1 locus with reduced plasma levels of LDL-C and APOB as well as with substantial protection from coronary heart disease.”
3 of 3

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Citations

Cites

Show all 41 references

Research works printed but not linked: 2

  1. Stanford, 2009, J Clin Invest., 119, 3236
  2. Grundy, 1990, Dis Mon., 36, 641

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Metadata

Authors
Strong, A., Ding, Q., Edmondson, A. C., Millar, J. S., Sachs, K. V., Li, X., Kumaravel, A., Wang, M. Y., Ai, D., Guo, L., Alexander, E. T., Nguyen, D., Lund-Katz, S., Phillips, M. C., Morales, C. R., Tall, A. R., Kathiresan, S., Fisher, E. A., Musunuru, K., & Rader, D. J.
Affiliations
  • University of Pennsylvania (US)
  • Harvard University (US)
  • Columbia University Irving Medical Center (US)
  • Children's Hospital of Philadelphia (US)
  • Massachusetts General Hospital (US)
Corresponding author
Rader, Daniel J.
Venue
Journal of Clinical Investigation
Published
2012-08-01
Volume
122
Issue
8
Pages
2807-2816
ISSN
0021-9738 (ISSN-L)
OpenAlex
W2071039886
Cited by
222
References
41
Citations by year
2026: 11 · 2025: 5 · 2024: 5 · 2023: 8 · 2022: 19 · 2021: 15 · 2020: 13 · 2019: 20 · 2018: 11 · 2017: 23 · 2016: 18 · 2015: 23 · 2014: 29 · 2013: 15 · 2012: 7
FWCI
9.39
Type
journal article
Language
en
Open access
Locations
  • Journal of Clinical Investigation (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • American Heart Association
  • University of Pennsylvania
  • Strong
  • National Heart, Lung, and Blood Institute (RC2HL101864, R01HL109489, K99HL098364)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Cholesterol and Lipid Metabolism
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Lipoproteins and Cardiovascular Health
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Lipid metabolism and disorders
Keywords
sortilin, SORT1, apolipoprotein B secretion, LDL catabolism, LDL receptor, lysosomal targeting, hepatic lipid metabolism, LDL cholesterol, myocardial infarction risk, Golgi apparatus, lysosomal degradation
MeSH terms
APOBEC-1 Deaminase, Sortilin, Animals, Apolipoproteins B, Base Sequence, Cell Line, Cytidine Deaminase, Humans, Hydrogen-Ion Concentration, Kinetics, Lipoproteins, LDL, Lipoproteins, VLDL, Liver, Lysosomes, Mice, Transgenic, Models, Biological, Receptors, LDL, Recombinant Proteins, Mutagenesis, Site-Directed, DNA Primers, Mice, Knockout, Adaptor Proteins, Vesicular Transport, Mice

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