Cited by 485Neuroinflammation and Neurodegeneration MechanismsAlzheimer's disease research and treatmentsPhagocytosis and Immune Regulation

Microglia use TAM receptors to detect and engulf amyloid β plaques

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Huang, Youtong, Happonen, Kaisa E., Burrola, Patrick G., O’Connor, Carolyn, Hah, Nasun, Huang, Ling, Nimmerjahn, Axel, Lemke, Greg·2021·Nature Immunology

Abstract

Two microglial TAM receptor tyrosine kinases, Axl and Mer, have been linked to Alzheimer's disease, but their roles in disease have not been tested experimentally. We find that in Alzheimer's disease and its mouse models, induced expression of Axl and Mer in amyloid plaque-associated microglia was coupled to induced plaque decoration by the TAM ligand Gas6 and its co-ligand phosphatidylserine. In the APP/PS1 mouse model of Alzheimer's disease, genetic ablation of Axl and Mer resulted in microglia that were unable to normally detect, respond to, organize or phagocytose amyloid-β plaques. These major deficits notwithstanding, TAM-deficient APP/PS1 mice developed fewer dense-core plaques than APP/PS1 mice with normal microglia. Our findings reveal that the TAM system is an essential mediator of microglial recognition and engulfment of amyloid plaques and that TAM-driven microglial phagocytosis does not inhibit, but rather promotes, dense-core plaque development.

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Crossref · 10.1038/s41590-021-00913-5

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  • Microglia are required for the consolidation of neurotoxic soluble Aβ oligomers into more inert insoluble fibrils and for construction into compact plaques.

    “Microglia are required for the consolidation of neurotoxic soluble Aβ oligomers into more inert insoluble fibrils and for construction into compact plaques (Brown et al., 2020; Huang et al., 2021; Martin et al., 1994).”

    From SYK coordinates neuroprotective microglial responses in neurodegenerative disease (2022) · cites this paper as Huang et al., 2021

    The Discussion (page not provided) suggests that phagocytic microglia construct dense-core plaques from loosely organized Aβ material, and the Results report fewer such plaques when TAM signaling is absent. But the paper frames confinement of toxic pre-plaque oligomers as a hypothesis; it does not establish the claimed conversion of soluble oligomers into more inert insoluble fibrils as a required process. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • Genetic deletion of any of these receptors in mouse models of AD results in less compact/more diffuse plaques, and increased neuritic dystrophy around Aβ deposits.

    “Genetic deletion of any of these receptors in mouse models of AD resulted in less compact/more diffuse plaques, and increased neuritic dystrophy around Αβ deposits14,79.”

    From Amyloid-β induces lipid droplet-mediated microglial dysfunction via the enzyme DGAT2 in Alzheimer’s disease (2025) · cites this paper as [79]

    The Results (“TAM-dependent phagocytosis and shaping of plaques”; page unavailable) report more diffuse plaques and increased markers of dystrophic neuronal membranes after combined Axl and Mertk deletion in APP/PS1 mice. But the paper does not show these outcomes after deletion of any one receptor: in “Dense-core plaque burden in the absence of TAM signaling,” Mertk deletion largely reproduces the reduction in dense-core plaques, whereas Axl deletion does not reduce cortical plaque burden. (LLM, conf=0.90)

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  • Microglia limit diffuse plaques by constructing and maintaining dense compact-like plaque properties in AD mouse models and humans, thereby blocking the progression of neuritic dystrophy and reducing tau phosphorylation in the local plaque environment.

    “Furthermore, microglia limit diffuse plaques by constructing and maintaining dense compact-like plaque properties in AD mouse models and humans, thereby blocking the progression of neuritic dystrophy and reducing tau phosphorylation in the local plaque environment [12, 38, 106].”

    From Enhanced microglial dynamics and a paucity of tau seeding in the amyloid plaque microenvironment contribute to cognitive resilience in Alzheimer’s disease (2024) · cites this paper as [38]

    Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

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  • Filamentous plaques are neurotoxic whereas compact dense-core plaques are relatively benign.

    “Interestingly, it was previously reported that filamentous plaques are neurotoxic whereas compact dense-core plaques are relatively benign [38, 52].”

    From Enhanced microglial dynamics and a paucity of tau seeding in the amyloid plaque microenvironment contribute to cognitive resilience in Alzheimer’s disease (2024) · cites this paper as [38]

    The Results section reports that markers of dystrophic neuronal membranes increased mainly around diffuse plaques, but also around dense-core plaques. The Discussion proposes that dense-core plaques may confine toxic Aβ oligomers; it does not establish that filamentous plaques are neurotoxic while compact plaques are relatively benign. No page numbers are available in our copy. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • Genetic ablation of tyrosine kinase TAM receptors inhibited microglial phagocytosis and decreased dense-core plaque density in the cortex and hippocampus after 12 months of age; these changes were not due to any changes in the production of Aβ peptides.

    “Using the APP/PS1 AD mouse model, Huang et al. showed that genetic ablation of tyrosine kinase TAM receptors inhibited microglial phagocytosis and decreased dense-core plaque density in the cortex and hippocampus after 12 months of age; these changes were not due to any changes in the production of Aβ peptides [38].”

    From Enhanced microglial dynamics and a paucity of tau seeding in the amyloid plaque microenvironment contribute to cognitive resilience in Alzheimer’s disease (2024) · cites this paper as [38]

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Authors
Huang, Y., Happonen, K. E., Burrola, P. G., O’Connor, C., Hah, N., Huang, L., Nimmerjahn, A., & Lemke, G.
Affiliations
Salk Institute for Biological Studies (US)
Corresponding author
Lemke, Greg
Venue
Nature Immunology
Published
2021-04-15
Volume
22
Issue
5
Pages
586-594
ISSN
  • 1529-2908 (ISSN-L)
  • 1529-2916
OpenAlex
W3152525961
Cited by
483
References
62
Citations by year
2026: 60 · 2025: 96 · 2024: 99 · 2023: 86 · 2022: 109 · 2021: 33
FWCI
32.65
Type
journal article
Language
en
Open access
Locations
  • Nature Immunology (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
U.S. Department of Health & Human Services | National Institutes of Health (AG060748, NS083038, NS108034, NS103522, AG062429, CA014195, OD023689)
Topics
  • Life Sciences › Neuroscience › Neurology › Neuroinflammation and Neurodegeneration Mechanisms
  • Health Sciences › Medicine › Physiology › Alzheimer's disease research and treatments
  • Life Sciences › Immunology and Microbiology › Immunology › Phagocytosis and Immune Regulation
Keywords
microglia, TAM receptors, AXL, Mer, Alzheimer's disease, amyloid plaques, microglial phagocytosis, Gas6, phosphatidylserine, APP/PS1 mice, receptor tyrosine kinase
MeSH terms
Intravital Microscopy, c-Mer Tyrosine Kinase, RNA-Seq, Axl Receptor Tyrosine Kinase, Alzheimer Disease, Animals, Brain, Disease Models, Animal, Female, Humans, Male, Phagocytosis, Proto-Oncogene Proteins, Amyloid beta-Peptides, Amyloid beta-Protein Precursor, Microglia, Mice, Knockout, Microscopy, Confocal, Receptor Protein-Tyrosine Kinases, Microscopy, Fluorescence, Multiphoton, Mice, Presenilin-1, Single-Cell Analysis

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