Single-cell sequencing reveals that AK5 inhibits apoptosis in AD oligodendrocytes by regulating the AMPK signaling pathway

Abstract

Background: Neuroinflammation and abnormal energy metabolism have been shown to significantly contribute to the progression of Alzheimer's disease (AD). Adenylate kinase 5 (AK5), an enzyme predominantly expressed in the brain regulates ATP metabolism, has an unclear role in energy metabolism and neuroinflammation in AD.

Methods: The AD datasets were derived from the GEO public database to analyze the expression levels of AK5 in AD and normal samples and to assess the relationship between AK5 expression and the clinical characteristics of AD patients. Functional enrichment analysis was employed to investigate the effects of changes in AK5 expression on energy metabolism and immunoinflammation in AD, as well as the underlying mechanisms. Moreover, the influence of AK5 expression variations on oligodendrocyte development was assessed, and the predicted outcomes were validated through cellular experiments.

Results: Bioinformatic analysis revealed that AK5 was lowly expressed in AD olfactory lobe tissues, accompanied by increased immunoinflammation and apoptosis. Increased expression of AK5 was associated with the activation of AMPK signaling, enhanced oxidative phosphorylation, and overall stimulation of energy metabolism. In oligodendrocytes treated with Aβ1-42, overexpression of AK5 resulted in elevated levels of P-AMPK, SIRT1, and BCL-2 proteins, while reducing the levels of BAX, CASPASE-3, and NF-κB proteins. This modulation activated AMPK signaling, thereby inhibiting neuroinflammation and apoptosis. In contrast, low levels of AK5 expression during early differentiation triggered inflammatory responses and increased apoptosis in oligodendrocytes.

Conclusion: AK5 inhibits AD oligodendrocyte apoptosis by activating the AMPK signaling pathway.

Keywords: AMPK signalling pathway; AdenylateKinase 5; Alzheimer’s disease; Apoptosis; Oligodendrocyte.

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Fig. 1

AK5 is lowly expressed in AD patients and is associated with neuroinflammation via abnormal energy metabolism. A Batch correction on the GSE48350, GSE26927 and GSE5281 datasets; B Differential analysis of AK5 expression in AD and normal control samples; Differential analysis of AK5 expression among ApoE subtypes; Differential analysis of AK5 expression among different Braak stage subgroups; C Univariate and multivariate analyses of clinical characteristics of AD patients and AK5 gene expression in relation to the risk of AD; D Gene differential analysis between AD and control samples; E DO enrichment analysis of AK5-related differential genes; F KEGG enrichment analysis made by AK5-related differential genes; G GO enrichment analysis of AK5-related differential genes. **P < 0.01

Fig. 2

Correlation analysis of AK5 expression with immune cell infiltration and inflammation score. A Analysis of immune cell infiltration in AD samples by AK5 high and low expression groups; B Correlation analysis between AK5 and infiltrating immune cells in AD samples; C Analysis of the difference of inflammation scores between AD and control samples; D Correlation analysis between AK5 and inflammation scores in AD samples. **P < 0.01

Fig. 3

Single-cell sequencing shows AK5 suppresses neuroinflammation through energy metabolism. A, B Sample source and cell clustering; C Expression of cellular markers for microglia, endothelial cells, oligodendrocyte precursor cells, neuronal cells and oligodendrocytes in clustered cells; D Distribution of six types of cells; E The distribution of the six cell types in each sample; F Expression of AK5 in six types of cells; G Expression and differential analyses of AK5 in control and AD samples; H GSVA analysis between AK5-positive and AK5-negative cells in AD samples; I Differential gene KEGG enrichment analysis between AK5-positive and AK5-negative cells

Fig. 4

Low AK5 expression inhibits oligodendrocyte cell differentiation and promotes apoptosis. A The cluster of oligodendrocytes and the expression of AK5 in oligodendrocytes; B Distribution of AD and control samples in oligodendrocytes and differential analysis of AK5 between AD and control samples; C KEGG enrichment analysis of differential genes between AD and control samples; D Clustering and grouping of oligodendrocytes in AD samples; E Expression and distribution of AK5 in oligodendrocytes; F Volcanic map of differential genes between AK5-positive oligodendrocytes and AK5-negative oligodendrocytes in AD samples; G KEGG enrichment analysis of differential genes between AK5-positive oligodendrocytes and AK5-negative oligodendrocytes in AD samples

Fig. 5

The influence of AK5 expression on oligodendrocyte development in pseudo-temporal sequence. A Pseudotime series analysis of oligodendrocytes in control group; B Changes of AK5 expression during the oligodendrocyte development; C Enrichment analysis of genes expressed early in oligodendrocyte development in the control group; D Pseudotime series analysis of oligodendrocytes in AD group; E Changes of AK5 expression during oligodendrocyte development; F Enrichment analysis of genes expressed early in oligodendrocyte development in the AD group

Fig. 6

Cellular assay showing AK5 inhibition of oligodendrocyte apoptosis through AMPK signalling activation. A, B mRNA (A) and protein (B) expression levels of AK5 in Aβ1-42-induced MO3.13 cells compared to control; C CCK8 assay showing changes in the survival rate of Aβ1-42-induced cells due to Ak5 overexpression and knockdown; D, E Apoptosis assay examining effects of AK5 overexpression and knockdown on apoptosis of Aβ1-42-induced cells; F Effects of AK5 overexpression and knockdown on protein expression abundance of P-AMPK, SITR1, P53, NF-KB in the AMPK pathway, and BAX, BCL-2, CASPASE3 in the apoptotic pathway