Cited by 756Alzheimer's disease research and treatmentsDementia and Cognitive Impairment ResearchNeuroinflammation and Neurodegeneration Mechanisms

ApoE in Alzheimer’s disease: pathophysiology and therapeutic strategies

Open access
Raulin, Ana-Caroline, Doss, Sydney V., Trottier, Zachary A., Ikezu, Tadafumi C., Bu, Guojun, Liu, Chia-Chen·2022·Molecular Neurodegeneration

Abstract

Alzheimer’s disease (AD) is the most common cause of dementia worldwide, and its prevalence is rapidly increasing due to extended lifespans. Among the increasing number of genetic risk factors identified, the apolipoprotein E ( APOE ) gene remains the strongest and most prevalent, impacting more than half of all AD cases. While the ε4 allele of the APOE gene significantly increases AD risk, the ε2 allele is protective relative to the common ε3 allele. These gene alleles encode three apoE protein isoforms that differ at two amino acid positions. The primary physiological function of apoE is to mediate lipid transport in the brain and periphery; however, additional functions of apoE in diverse biological functions have been recognized. Pathogenically, apoE seeds amyloid-β (Aβ) plaques in the brain with apoE4 driving earlier and more abundant amyloids. ApoE isoforms also have differential effects on multiple Aβ-related or Aβ-independent pathways. The complexity of apoE biology and pathobiology presents challenges to designing effective apoE-targeted therapeutic strategies. This review examines the key pathobiological pathways of apoE and related targeting strategies with a specific focus on the latest technological advances and tools.

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Registry

Crossref · 10.1186/s13024-022-00574-4

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319 of 319 references verified0 citation errors · 0 not checkable

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  • In humans, three major isoforms of APOE are lipidated in an isoform-specific manner (ε2 > ε3 > ε4).

    “In humans, three major isoforms of APOE are lipidated in an isoform‐specific manner (ε2 > ε3 > ε4). 9 , 48”

    From Deletion of miR-33, a regulator of the ABCA1–APOE pathway, ameliorates neuropathological phenotypes in APP/PS1 mice (2024) · cites this paper as [48]

    The “APOE biology: synthesis, structure, and function” section identifies three major human apoE isoforms and says their differences affect lipid binding. “ApoE in dysregulation of lipid metabolism” reports an apoE2 > apoE3 > apoE4 ranking for cholesterol and phosphatidylcholine efflux in rat cells, not for the degree to which the isoforms are lipidated in humans. The claimed human lipidation ranking is therefore not established by these passages (page numbers unavailable). (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • APOE binds to cell surface receptors including LDLR, LRP1, VLDLR, and APOER2.

    “APOE binds to cell surface receptors, such as low‐density lipoprotein receptor (LDLR), LDLR‐related protein 1 (LRP1), very low‐density lipoprotein receptor (VLDLR), and apolipoprotein E receptor 2 (APOER2 or LRP8). 2 , 14 , 15”

    From Deletion of neuronal <i>Idol</i> ameliorates Alzheimer's disease–related pathologies via APOE receptors (2025) · cites this paper as [2]

    The “APOE biology: synthesis, structure, and function” section says apoE binds cell-surface receptors including LDLR and LRP1. The passages found do not identify VLDLR or APOER2 (LRP8) as apoE-binding receptors; the paper’s mention of VLDL refers to a lipoprotein, not its receptor. (LLM, conf=0.87)

    Experimental — accuracy not yet measured
  • APOE is mainly secreted by astrocytes but is also expressed in microglia, neurons, and oligodendrocytes, particularly under injury and degenerative conditions.

    “Although mainly secreted by astrocytes, APOE is also expressed in microglia, neurons, and oligodendrocytes, particularly under injury and degenerative conditions. 2 , 13”

    From Deletion of neuronal <i>Idol</i> ameliorates Alzheimer's disease–related pathologies via APOE receptors (2025) · cites this paper as [2]

    The Physiological function of apoE section says apoE expression rises in activated microglia and stressed neurons under pathological conditions and injury, and that oligodendrocytes express it more abundantly after injury. It also says astrocytes express and secrete apoE, but does not establish that astrocytes are its main source of secretion. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • Genetic variants of many differentially expressed genes identified in this study, such as CLU and APOE, have been associated with increased Alzheimer's disease risk.

    “Genetic variants of many of the differentially expressed genes identified in this study, such as CLU and APOE, have been associated with increased Alzheimer’s disease risk58,59.”

    From mTORC1 drives cell-autonomous astrocyte reactivity in tuberous sclerosis (2026) · cites this paper as [59]

    The section ‘ApoE isoform is a risk determinant for AD and related dementias’ states that APOE4 increases Alzheimer’s disease risk. The passages from this paper do not establish the corresponding risk association for CLU or for the broader group of genes named in the citing sentence. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • The APOE-ε4 allele increases Alzheimer's disease risk three- to eightfold compared to the neutral ε3 allele, while ε2 confers relative protection.

    “The APOE-ε4 allele increases AD risk three- to eightfold compared to the neutral ε3 allele, while ε2 confers relative protection [154].”

    From Toward a Unified Framework in Molecular Neurobiology of Alzheimer’s Disease: Revisiting the Pathophysiological Hypotheses (2026) · cites this paper as [154]

    The section “ApoE isoform is a risk determinant for AD and related dementias” (page unavailable) states that APOE4 increases AD risk and APOE2 reduces it by almost half. It does not give the claimed three- to eightfold increase relative to APOE3; instead, it reports an increase of up to 15-fold in APOE4 homozygotes. (LLM, conf=0.88)

    Experimental — accuracy not yet measured

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Authors
Raulin, A.-C., Doss, S. V., Trottier, Z. A., Ikezu, T. C., Bu, G., & Liu, C.-C.
Affiliations
Mayo Clinic in Florida (US)
Corresponding author
  • Bu, Guojun
  • Liu, Chia-Chen
Venue
Molecular Neurodegeneration
Published
2022-11-08
Volume
17
Issue
1
Pages
72-72
ISSN
1750-1326 (ISSN-L)
OpenAlex
W4308572221
Cited by
756
References
317
Citations by year
2026: 222 · 2025: 266 · 2024: 187 · 2023: 81
FWCI
18.38
Type
journal article
Language
en
Open access
Locations
  • Molecular Neurodegeneration (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
  • Rare & Special e-Zone (The Hong Kong University of Science and Technology) (submittedVersion)
Funders
  • NIH Blueprint for Neuroscience Research (R37AG027924, RF1AG057181, U19AG069701, U19AG069701, R01AG062110)
  • Cure Alzheimer’s Fund (Cure Alzheimer’s Fund)
Topics
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Health Sciences › Medicine › Psychiatry and Mental health › Dementia and Cognitive Impairment Research
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
Keywords
apolipoprotein E, Alzheimer's disease, APOE ε4, APOE isoforms, amyloid plaques, lipid transport, genetic risk factors
MeSH terms
Alleles, Alzheimer Disease, Apolipoproteins E, Humans, Amyloid beta-Peptides, Apolipoprotein E4, Plaque, Amyloid

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