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β2-Microglobulin coaggregates with Aβ and contributes to amyloid pathology and cognitive deficits in Alzheimer’s disease model mice

Abstract

Extensive studies indicate that β-amyloid (Aβ) aggregation is pivotal for Alzheimer’s disease (AD) progression; however, cumulative evidence suggests that Aβ itself is not sufficient to trigger AD-associated degeneration, and whether other additional pathological factors drive AD pathogenesis remains unclear. Here, we characterize pathogenic aggregates composed of β2-microglobulin (β2M) and Aβ that trigger neurodegeneration in AD. β2M, a component of major histocompatibility complex class I (MHC class I), is upregulated in the brains of individuals with AD and constitutes the amyloid plaque core. Elevation of β2M aggravates amyloid pathology independent of MHC class I, and coaggregation with β2M is essential for Aβ neurotoxicity. B2m genetic ablation abrogates amyloid spreading and cognitive deficits in AD mice. Antisense oligonucleotide- or monoclonal antibody-mediated β2M depletion mitigates AD-associated neuropathology, and inhibition of β2M–Aβ coaggregation with a β2M-based blocking peptide ameliorates amyloid pathology and cognitive deficits in AD mice. Our findings identify β2M as an essential factor for Aβ neurotoxicity and a potential target for treating AD.

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Fig. 1: β2M co-sediments with Aβ and accelerates amyloid deposition in an MHC class I-independent manner.
Fig. 2: B2m deficiency ameliorates cognitive deficits and prevents spreading of amyloid pathology in 5×FAD mice.
Fig. 3: B2m deficiency abrogates oAβ-induced neurotoxicity in vivo.
Fig. 4: B2M ASO or anti-β2M antibody reduces amyloid pathology in 5×FAD mice.
Fig. 5: Peripheral clearance of β2M ameliorates amyloid pathology in 5×FAD mice.
Fig. 6: Systemic injection of anti-β2M antibody ameliorates neuropathology in 5×FAD mice.
Fig. 7: Coaggregation with β2M promotes Aβ aggregation.
Fig. 8: Blocking β2M–Aβ coaggregation abrogates Aβ aggregation and neurotoxicity.

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Data availability

The datasets generated and/or analyzed in the current study are within the manuscript or the Supplementary Information. The bulk RNA-sequencing data were deposited in the CNGB Sequence Archive of the China National GeneBank Database with the accession number CNP0003897. Source data are provided with this paper.

Code availability

No custom software code was used.

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Acknowledgements

We thank G. Fu, Y. Shen, C. Xiao and N. Xiao for sharing experimental resources. We thank Y. Zhao, L. Zhong, L. Yao, C. Wu, Q. Liu, X. You, J. Huang, B. Xie, Q. Deng, T. Guo, H. Zhang, S. Zhang and X. Sheng for technical assistance. This work was supported by National Natural Science Foundation of China (U21A20358, 81822014 and 31871077 to X.W.), the National Key R&D Program of China (2021YFA1101401 and STI2030-Major Projects-2021ZD0202400 to X.W.), National Natural Science Foundation of China (82271451 and 81701130 to Q.Z.; 81701349 to H.Z.; 81802823 to Y. Zhou), Natural Science Foundation of Fujian Province of China (2021J02004 and 2017J06021 to X.W.; 2018J01054 to Y. Zhou), Guangdong Basic and Applied Basic Research Foundation (2021B1515120081 to X.W.), Science Innovation 2030-Brain Science and Brain-Inspired Intelligence Technology Major Projects (2021ZD0201103 and 2021ZD0201803 to X.-X.Y.) and Fundamental Research Funds for the Chinese Central Universities (20720220052 to Q.Z.). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Author information

Authors and Affiliations

Authors

Contributions

X.W. conceived the study and designed the experiments. Y. Zhao performed most studies and data analyses. Y.H. performed two-photon microscopy and analyzed the data. J.H. and C.L. performed the BLI assay and analyzed the data. M.L. performed the ASO screening experiment. Q.Z., Y.G., H.Z., Y. Zhou, X.Z., H.L. and H.S. analyzed the data and contributed reagents, materials and analysis tools. Y.-J.W. and X.-X.Y. provided human brain or plasma samples. X.W. and Y. Zhao wrote the manuscript. T.Y.H., H.X. and C.L. edited the manuscript. X.W. supervised the project. All authors reviewed the manuscript.

Corresponding author

Correspondence to Xin Wang.

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Competing interests

Y. Zhao, Q.Z., Y.G., M.L. and X.W. have filed a patent application based on this work. The remaining authors declare no competing interests.

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Nature Neuroscience thanks Adriano Aguzzi, Li Gan, and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 NF-κB pathway-mediated B2M overproduction in activated microglia.

a, Quantification of Aβ42 levels in human cortex by ELISA (AD, n = 27; control, n = 8; two-sided unpaired Mann Whitney test). b, c, Immunoblot (b) and quantification of B2M, APP and β-actin (as loading control) in the hippocampus from 3- to 15-month-old 5×FAD mice and WT mice (n = 3 mice per group; B2M: two-sided two-way ANOVA followed by Bonferroni’s multiple comparisons test; comparing each month with the 3-month-old WT). d, Strategy of humanized B2M knock-in (B2MKI/KI) mouse generation. e, Quantification of body weights of 2-month-old WT and B2MKI/KI mice (WT, n = 7 mice; B2MKI/KI, n = 8 mice; two-sided unpaired t-test). f, Representative immunostaining for microglia (Iba1), astrocytes (GFAP), neurons (TUJ1) and B2M (HA) in hippocampal CA1 region of 2-month-old B2MKI/KI mice (expressing human B2M with a C-terminal HA tag). g, Quantification of the percentages of double-positive cells in each cell type (microglia, n = 458 cells; astrocyte, n = 550 cells; neuron, n = 370 cells). h, Experimental schematic of B2m mRNA expression analysis in primary microglial cultures. i, Relative B2m mRNA expression levels in primary microglia under differing treatment conditions are shown in (h) (Control and oAβ, n = 3 biologically independent samples; LPS, n = 4 biologically independent samples; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test). j, Immunohistochemical analysis of B2M (anti-B2M antibody) and Aβ (thioflavin S) colocalization in 5×FAD mouse hippocampal sections. Similar results were observed in three independent experiments. The data represent means in (f) and mean ± s.e.m. in (a, c, g and i). The P values are indicated on the graphs. For detailed statistical information, see Source Data.

Source data

Extended Data Fig. 2 Overexpression of B2M accelerates amyloid deposition in the hippocampus of 5×FAD mice.

a, Schematic of the AAV viral vector expressing human B2M. b, Confocal imaging of AAV-injected hippocampus labeled with mCherry. Similar results were observed in two independent experiments. c, d, Immunoblot analysis of B2M-HA, APP and β-actin (as a loading control) in the hippocampus of AAV-injected WT and 5×FAD mice (n = 5 mice per group; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test). e-g, Representative immunostaining images (e) and quantification of total Aβ immunostained area (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; two-sided unpaired Mann Whitney test) (f) and amyloid plaque number (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; 0–20 μm, 20–40 μm and total: two-sided unpaired t-test; >40 μm: two-sided unpaired Mann Whitney test) (g) in hippocampal DG region of AAV-injected 5×FAD mice. h, Quantification of total Aβ immunostained area (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; two-sided unpaired t-test) and amyloid plaque number (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; 0–15 μm and 15–30 μm: two-sided unpaired t-test; >30 μm and total: two-sided unpaired Mann Whitney test) in hippocampal CA1 region of AAV-injected 5×FAD mice. i, Quantification of Aβ42 levels in the hippocampus of AAV-injected 5×FAD mice by ELISA (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; two-sided unpaired t-test). j, k, Representative immunostaining images (j) and quantification of Lamp1-positive dystrophic neurites in hippocampal DG region of AAV-injected 5×FAD mice (AAV-Ctrl, n = 5 mice; AAV-B2M, n = 6 mice; two-sided unpaired t-test) (k). The P values are indicated on the graphs: mean ± s.e.m. For detailed statistical information, see Source Data.

Source data

Extended Data Fig. 3 Elevation of B2M promotes spreading of amyloid pathology.

a, Schematic of B2M injection experiments. Bilateral guide cannulas were implanted into hippocampal DG region of 4-month-old 5×FAD mice. Mice were injected with purified B2M (2 μl, 1 μg/μl) or PBS (2 μl, vehicle) every 7 days (four times in total within 28 days). b, Schematic of amyloid spreading analysis. The site of hippocampal injection at bilateral sites is shown; images from sections were sequentially quantified at 120 μ m distance intervals relative to the injection site. c, Quantification of rostro-caudal spreading of amyloid pathology. Number of amyloid deposits in the hippocampus of B2M-injected 5×FAD mice displayed for each section (n = 5 mice; two-sided paired t-test). d, e, Representative immunostaining (d) and quantification of Lamp1-positive dystrophic neurites in the hippocampus of B2M-injected 5×FAD mice (n = 5 mice; two-sided paired t-test) (e). f, Schematic of the AAV viral vector expressing BRI-Aβ42 fusion protein. BRI can be cleaved by furin to release human Aβ42 peptides in the mouse brain. g, Immunohistochemical analysis of amyloid plaques in 5×FAD mouse cortex using B2M, MHC-I and Aβ (6E10) antibodies. A liver section from a WT mouse was used as a positive control for MHC-I staining. Similar results were observed in three independent experiments. The P values are indicated on the graphs: mean ± s.e.m. For detailed statistical information, see Source Data.

Source data

Extended Data Fig. 4 B2m deficiency ameliorates amyloid pathology in 5×FAD mice.

a, Quantification of 6E10-positive amyloid plaques in hippocampal CA1 region (n = 5 mice per group; 0–20 μm and 20–40 μm: two-sided unpaired t-test; >40 μm: 5×FAD versus 5×FAD; B2m+/−, two-sided unpaired t-test; 5×FAD versus 5×FAD; B2m−/− and 5×FAD; B2m+/− versus 5×FAD; B2m−/−, two-sided unpaired Mann Whitney test; Aβ plaque number: two-sided unpaired t-test; Aβ plaque area: two-sided unpaired t-test). b, Representative immunostaining of 6E10-positive amyloid plaques in the cortex of 6-month-old 5×FAD, 5×FAD; B2m+/− and 5×FAD; B2m−/− mice. c, d, Quantification of total Aβ immunostained area (n = 5 mice per group; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test) (c) and amyloid plaque number (n = 5 mice per group; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test) (d) in (b). e, Representative immunostaining of amyloid plaques in the hippocampus and cortex of 12-month-old 5×FAD and 5×FAD; B2m−/− mice. f-h, Quantification of amyloid plaques in hippocampal DG (5×FAD, n = 4 mice; 5×FAD; B2m−/−, n = 3 mice; two-sided unpaired t-test) (f) and CA1 (5×FAD, n = 4 mice; 5×FAD; B2m−/−, n = 3 mice; two-sided unpaired t-test) (g) region and the cortex (5×FAD, n = 4 mice; 5×FAD; B2m−/−, n = 3 mice; two-sided unpaired t-test) (h). i, Quantification of Aβ42 in the hippocampus from 12-month-old 5×FAD and 5×FAD; B2m−/− mice by ELISA (5×FAD, n = 4 mice; 5×FAD; B2m−/−, n = 3 mice; two-sided unpaired t-test). The P values are indicated on the graphs: mean ± s.e.m. For detailed statistical information, see Source Data.

Source data

Extended Data Fig. 5 B2m deficiency ameliorates the loss of dendritic spines and spreading of amyloid pathology in 5×FAD mice.

a, Immunoblot analysis of APP, APP-CTFs, APP processing- and Aβ degrading-enzymes in the cortex of 6- to 7-month-old B2m+/+, B2m+/−, 5×FAD and 5×FAD; B2m+/− mice. b, Quantification of APP, B2M, PS-NTF, BACE1, APP-CTF, ADAM17, IDE, NEP (n = 5 mice per genotype; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test for B2M, APP-CTF, ADAM17, BACE1, PS1-NTF and IDE; two-sided Kruskal–Wallis test followed by Dunn’s multiple comparisons test for APP and NEP) and β-actin (as loading control). c, Golgi staining and quantification of dendritic spines in hippocampal CA1 region of 6- to 7-month-old mice (the number of counted dendrites is indicated on the graphs, n = 4 mice per group; two-sided Kruskal–Wallis test followed by Dunn’s multiple comparisons test). d, Golgi staining and quantification of dendritic spines in hippocampal DG region of 6- to 7-month-old mice (the number of counted dendrites is indicated on the graphs, n = 4 mice per group; two-sided Kruskal–Wallis test followed by Dunn’s multiple comparisons test). e, f, Quantification of the rostro-caudal spreading of Aβ pathology. Number of amyloid deposits displayed for each section (n = 6 mice; two different lysates: two-sided paired t-test; lysate + IgG: for -3, -1, 2 and 3: two-sided paired t-test; for -2 and 1: two-sided Wilcoxon matched-pairs signed rank test). The P values are indicated on the graphs: mean ± s.e.m. For detailed statistical information, see Source Data.

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Extended Data Fig. 6 B2m deficiency alters learning and memory-related transcriptional profiles in oAβ-injected mice.

a, Schematic of oAβ injection and RNAseq analysis. Two- to three-month-old WT and B2m−/− mice were ICV injected with oligomeric Aβ42 (oAβ) or PBS (Vehicle). Hippocampal tissues were dissected, and total RNA was isolated, purified and sequenced. n = 3 mice per group. b, Volcano plots with genes that were significantly downregulated (blue) or upregulated (red) in the hippocampus of oAβ-injected 2- to 3-month-old B2m−/− versus WT mice (fold change > 1.5, P value < 0.05) (two-tailed Wald test). c, GO analysis of upregulated genes in the oAβ-injected B2m−/− mouse hippocampus (hypergeometric test, qvalueCutoff = 0.05). d, GO analysis of downregulated genes in the oAβ-injected B2m−/− mouse hippocampus (hypergeometric test, qvalueCutoff = 0.05). e, Heatmap depicting upregulated genes in the oAβ-injected B2m−/− mouse hippocampus.

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Extended Data Fig. 7 Hippocampal injection of an anti-B2M monoclonal antibody ameliorates neuropathology in 5×FAD and APP/PS1 mice.

a, Body weights of B2M/Control ASO-injected and non-injected 5×FAD; B2MKI/KI mice (n = 3 mice per group; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test). b, Quantification of 6E10-positive amyloid plaques in hippocampal CA1 region of antibody-injected 5×FAD mice (5×FAD + Iso-IgG, n = 5 mice; 5×FAD + Anti-B2M-IgG, n = 7 mice; two-sided unpaired t-test). c, d, Representative immunostaining images (c) and quantification of Lamp1-labeled dystrophic neurites in hippocampal DG region of 5×FAD mice injected with antibodies as indicated (5×FAD + Iso-IgG, n = 5 mice; 5×FAD + Anti-B2M-IgG, n = 7 mice; two-sided unpaired t-test) (d). e, Immunoblot and quantification of B2M, APP and β-actin (as a loading control) in the hippocampus of 9-month-old APP/PS1 and WT mice (n = 4 mice per group; two-sided unpaired t-test). f, Immunohistochemical analysis of B2M-Aβ coaggregation in the hippocampus of 12-month-old APP/PS1 mice using B2M (anti-B2M) and Aβ (6E10) antibodies. Similar results were observed in two independent experiments. g, Bilateral guide cannulas were implanted into hippocampal DG region of 7-month-old APP/PS1 mice. The mice received anti-B2M IgG (2 μl, 1 μg/μl) or iso-type IgG (2 μl, vehicle) injections every 7 days (six times in total within 42 days). h, i, Representative immunostaining images (h) and quantification of 6E10-positive amyloid plaques in the hippocampus of antibody-injected APP/PS1 mice (n = 5 mice; two-sided paired t-test) (i). j, k, Representative immunostaining (j) and quantification of Lamp1-positive dystrophic neurites in the hippocampus of antibody-injected APP/PS1 mice (n = 5 mice; two-sided paired t-test) (k). l, Quantification of anti-B2M antibody levels in the plasma of parabiotic or non-parabiotic B2m−/− mice (n = 4 mice per group; two-sided unpaired t-test). The P values are indicated on the graphs: mean ± s.e.m. For detailed statistical information, see Source Data.

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Extended Data Fig. 8 B2M interacts with and promotes Aβ neurotoxicity.

a, Co-IP of endogenous Aβ42 and B2M in 12-month-old WT and 5×FAD mouse cortex. Similar results were observed in two independent experiments. b, c, Co-IP between synthetic Aβ42 and purified B2M. Similar results were observed in two independent experiments. d, e, Binding profiles of monomeric or oligomeric Aβ42 to different concentrations of B2M were determined by the BLI assay. The association and dissociation profiles are divided by the vertical dashed line. BLI was independently repeated three times. f, ThT fluorescence assay of purified B2M at various concentrations indicates that B2M does not self-aggregate. ThT assays were independently repeated three times for each condition, and the data represent mean values. g, CCK8 assay testing the cell viability of WT primary neurons exposed to B2M (0.2 μM), oAβ (2 μM) or oAβ + B2M (2 μM Aβ together with 0.2 μM B2M) for 24 hours (control and B2M n = 5 biologically independent samples, oAβ and Aβ + B2M n = 10 biologically independent samples; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test). h, Representative immunostaining of MAP2 in WT primary neurons treated with B2M (0.2 μM), oAβ (2 μM) or oAβ + B2M (2 μM Aβ together with 0.2 μM B2M) for 24 hours. i, j, Quantification of total neurite length (control, n = 22 cells; B2M, n = 23 cells; oAβ, n = 23 cells; Aβ + B2M, n = 22 cells; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test) (i) and branching (control, n = 29 cells; B2M, n = 23 cells; oAβ, n = 23 cells; Aβ + B2M, n = 23 cells; two-sided two-way ANOVA followed by Tukey’s multiple comparisons test; oAβ versus oAβ + B2M) (j) of the WT primary neurons with different treatments in (h). k, Experimental schematic of Il1b and Il6 mRNA expression analysis and microsphere uptake analysis in primary microglia. l, Representative immunostaining images showing microsphere uptake in primary microglia. m, Quantification of microsphere uptake in primary microglia under different treatment conditions (DMSO, n = 159 cells; oAβ, n = 153 cells; oAβ + B2M, n = 185 cells; two-sided Kruskal–Wallis test followed by Dunn’s multiple comparisons test), as shown in (k). n, Relative Il1b and Il6 mRNA expression levels in primary microglia under different treatment conditions (n = 4 biologically independent samples; two-sided one-way ANOVA followed by Tukey’s multiple comparisons test), as shown in (k). With the exception of those in (f) and (m), the data represent mean ± s.e.m. The P values are indicated on the graphs. For detailed statistical information, see Source Data.

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Extended Data Fig. 9 The P3 peptide blocks B2M-Aβ coaggregation and neurotoxicity.

a, Immunoblot analysis of Aβ42 oligomer formation. The P3 peptide blocks B2M-induced Aβ42 oligomer formation (This assay was independently repeated seven times; two-sided unpaired Mann Whitney test). b, Co-IP between synthetic Aβ42 and P3 peptides. Similar results were observed in two independent experiments. c, Schematic of the truncated P3 peptides. Three P3-derived subfragments were designed and synthesized based on the P3 β-sheet structure: P3-1 (aa 51–60), P3-2 (aa 61–75) and P3-3 (aa 61–69). d, ThT fluorescence assay for protein aggregation. Truncated P3 peptides were incubated with Aβ42 in the presence of full-length B2M. ThT assays were independently repeated three times, and the data represent the mean values. e, Cell viability of primary neurons treated with the P3 peptide was determined by CCK8 assay. Cultured primary neurons from C57BL/6 mice were incubated with increasing concentrations of P3 or scrambled peptide for 24 hours (n = 5 biologically independent samples per group; two-sided unpaired t-test; Ctrl versus Scrambled peptide or P3 peptide). f, Schematic for the aggregates and peptide injection and Golgi staining assay. g, Schematic for peptide injection and behavioral analysis. h, MWM probe test results (n = 8 mice per group; Platform cross number: two-sided unpaired t-test; Time in quadrant: two-sided unpaired Mann Whitney test). i, Schematic for peptide injection and immunostaining analysis. j, Immunoblot analysis of B2M in the hippocampus of peptide-injected 5×FAD; B2MKI/KI mice (n = 5 mice per group; two-sided unpaired t-test). With the exception of the ThT fluorescence data in (d), the data represent mean ± s.e.m. The P values are indicated on the graphs. For detailed statistical information, see Source Data.

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Extended Data Fig. 10 B2M is an essential factor for Aβ neurotoxicity and a novel target for therapeutic intervention in AD.

Elevation of B2M aggravates amyloid pathology independent of MHC-I, and coaggregation with B2M is essential for Aβ neurotoxicity. Importantly, both peripheral and brain B2M contribute to AD pathogenesis. Therapeutically, ASO or monoclonal antibody-mediated B2M depletion mitigates AD-associated neuropathology, and inhibiting B2M-Aβ coaggregation with a B2M-based blocking peptide ameliorates amyloid pathology and cognitive deficits in AD mice.

Supplementary information

Supplementary Information

Supplementary Figs. 1 and 2 and Tables 2 and 4–6 and titles for Supplementary Tables 1, 3 and 7 and Videos 1 and 2.

Reporting Summary

Supplementary Table 1

Mouse information for each experiment.

Supplementary Table 3

Information on the postmortem human brain samples.

Supplementary Table 7

Antibodies used in experiments.

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Supplementary Video 1

Two-photo imaging for the characterization of β2M.

Supplementary Video 2

Two-photo imaging for the characterization of anti-β2M antibody.

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Zhao, Y., Zheng, Q., Hong, Y. et al. β2-Microglobulin coaggregates with Aβ and contributes to amyloid pathology and cognitive deficits in Alzheimer’s disease model mice. Nat Neurosci 26, 1170–1184 (2023). https://doi.org/10.1038/s41593-023-01352-1

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