Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 25 (22), 4881-4897

Reduced Dynamin-Related Protein 1 Protects Against Phosphorylated Tau-induced Mitochondrial Dysfunction and Synaptic Damage in Alzheimer's Disease

Affiliations

Reduced Dynamin-Related Protein 1 Protects Against Phosphorylated Tau-induced Mitochondrial Dysfunction and Synaptic Damage in Alzheimer's Disease

Ramesh Kandimalla et al. Hum Mol Genet.

Abstract

The purpose of our study was to understand the protective effects of a partial reduction of dynamin-related protein 1 (Drp1) in Alzheimer’s disease (AD) progression and pathogenesis. Increasing evidence suggests that phosphorylated Tau and mitochondrial abnormalities are involved in the loss of synapses, defective axonal transport and cognitive decline, in patients with AD. In the current study, we investigated whether a partial reduction of Drp1 protect neurons from phosphorylated Tau-induced mitochondrial and synaptic toxicities in AD progression. We crossed Drp1+/− mice with Tau transgenic mice (P301L line) and created double mutant (TauXDrp1+/−) mice. Using real-time RT-PCR, immunoblotting and immunostaining analyses, we measured mRNA expressions and protein levels of genes related to the mitochondrial dynamics—Drp1 and Fis1 (fission), Mfn1, Mfn2 and Opa1 (fusion), CypD (matrix), mitochondrial biogenesis—Nrf1, Nrf2, PGC1α and TFAM and synaptic—synaptophysin, PSD95, synapsin 1, synaptobrevin 1, neurogranin, GAP43 and synaptopodin in brain tissues from 6-month-old Drp1+/−, Tau, TauXDrp1+/− and wild-type mice. Using biochemical and immunoblotting methods, mitochondrial function and phosphorylated Tau were measured. Decreased mRNA and protein levels of fission and matrix and increased levels of fusion, mitochondrial biogenesis, and synaptic genes were found in 6-month-old TauXDrp1+/− mice relative to Tau mice. Mitochondrial dysfunction was reduced in TauXDrp1+/− mice relative to Tau mice. Phosphorylated Tau found to be reduced in TauXDrp1+/− mice relative to Tau mice. These findings suggest that a partial reduction of Drp1 decreases the production of phosphorylated Tau, reduces mitochondrial dysfunction, and maintains mitochondrial dynamics, enhances mitochondrial biogenesis and synaptic activity in Tau mice. Findings of this study may have implications for the development of Drp1 based therapeutics for patients with AD and other tauopathies.

Figures

Figure 1
Figure 1
Immunoblotting analysis of mitochondrial dynamics and biogenesis proteins. (A) Shows representative immunoblotting analysis of 6-month-old WT, Drp1+/−, Tau and TauXDrp1+/− mice. (B) Shows quantitative densitometry analysis of mitochondrial dynamics and the matrix proteins Drp1, Fis1, Mfn1, Mfn2, Opa1 and CypD. (C) Shows quantitative densitometry analysis of mitochondrial biogenesis proteins PGC1α, Nrf1, Nrf1, and TFAM. The fission proteins Drp1 and Fis1 and matrix protein CypD were significantly increased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly decreased in Tau mice relative to WT mice, indicating the presence of abnormal mitochondrial dynamics. On the contrary, the fission proteins Drp1 and Fis1 and matrix protein CypD were significantly decreased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly increased TauXDrp1+/− mice relative to Tau mice, indicating that reduced Drp1 protects against phosphorylated Tau-induced mitochondrial dynamics toxicity.
Figure 1
Figure 1
Immunoblotting analysis of mitochondrial dynamics and biogenesis proteins. (A) Shows representative immunoblotting analysis of 6-month-old WT, Drp1+/−, Tau and TauXDrp1+/− mice. (B) Shows quantitative densitometry analysis of mitochondrial dynamics and the matrix proteins Drp1, Fis1, Mfn1, Mfn2, Opa1 and CypD. (C) Shows quantitative densitometry analysis of mitochondrial biogenesis proteins PGC1α, Nrf1, Nrf1, and TFAM. The fission proteins Drp1 and Fis1 and matrix protein CypD were significantly increased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly decreased in Tau mice relative to WT mice, indicating the presence of abnormal mitochondrial dynamics. On the contrary, the fission proteins Drp1 and Fis1 and matrix protein CypD were significantly decreased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly increased TauXDrp1+/− mice relative to Tau mice, indicating that reduced Drp1 protects against phosphorylated Tau-induced mitochondrial dynamics toxicity.
Figure 2
Figure 2
Immunoblotting analysis of phospho Tau and synaptic proteins. (A) Represents immunoblotting analysis. (B) Represents quantitative immunoblotting analysis. Synaptophysin and PSD95 proteins were significantly decreased in Tau mice relative to WT mice. On the contrary, synaptophysin and PSD95 proteins were increased in TauXDrp1+/− mice relative to Tau mice. Phosphorylated Tau protein is significantly decreased in TauXDrp1+/− mice relative to Tau mice.
Figure 3
Figure 3
Immunofluorescence analysis of mitochondrial dynamics proteins. (A) Represents immunofluorescence analysis. (B) Represents quantitative immunofluorescence analysis. The fission proteins Drp1 and Fis1 and matrix protein CypD were significantly increased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly decreased in Tau mice relative to WT mice. On the contrary, the fission proteins Drp1 and Fis1 and matrix protein CypD were significantly decreased; and the fusion proteins Mfn1, Mfn2, and Opa1 were significantly increased TauXDrp1+/− mice relative to Tau mice. These immunofluorescence findings agree with immunoblotting results.
Figure 4
Figure 4
Immunofluorescence analysis of mitochondrial biogenesis proteins. (A) Represents immunofluorescence analysis. (B) Represents quantitative immunofluorescence analysis. Significantly reduced levels of PGC1α (P = 0.03), Nrf1 (P = 0.001), Nrf2 (P = 0.03) and TFAM (P = 0.02) were found in Tau mice relative to WT mice. On the contrary, increased protein levels were found in PGC1α (P = 0.04), Nrf1 (P = 0.01), Nrf2 (P = 0.01) and TFAM (P = 0.01) in TauXDrp1+/− mice relative to Tau mice.
Figure 5
Figure 5
Immunofluorescence analysis of synaptic proteins. (A) Represents immunofluorescence analysis. (B) Represents quantitative immunofluorescence analysis. Synaptic proteins synaptophysin (P = 0.03) and PSD95 (P = 0.002) were significantly decreased in Tau mice relative WT mice (A, B). Synaptic proteins synaptophysin (P = 0.03) and PSD95 (P = 0.002) were significantly increased in TauXDrp1+/− mice relative Tau mice (A, B).
Figure 6
Figure 6
Immunofluorescence analysis of phosphorylated Tau in Tau mice and TauXDrp1+/− mice. (A) Represents immunofluorescence analysis. (B) Represents quantitative immunofluorescence analysis. Immunoreactivity levels of phosphorylated Tau were significantly reduced in TauXDrp1+/− mice relative to Tau mice (P = 0.003), indicating that a partial reduction of Drp1 reduces phosphorylated Tau in Tau mice.
Figure 7
Figure 7
Mitochondrial functional parameters in 6-month-old Drp1+/−, Tau, TauXDrp1+/− and WT mice. Mitochondrial function was assessed by measuring: (A) H2O2 production, (B) Lipid peroxidation, (C) Cytochrome oxidase activity (D) ATP levels, and (E) GTPase Drp1. The levels of H2O2 (P = 0.005) (A) and HNE (P = 0.04) (B) were significantly increased and the levels of cytochrome oxidase (P = 0.04) (C) and ATP (P = 0.02) (D) significantly decreased found in Tau mice relative to WT mice. The levels of H2O2 (P = 0.04) (A) and HNE (P = 0.04) (B) were significantly decreased and the levels of cytochrome oxidase (P = 0.02) (C) and ATP (P = 0.02) (D) significantly increased found in Tau/Drp1+/− mice relative to Tau mice. The levels of GTPase Drp1 activity was significantly reduced in Drp1+/− mice (P = 0.01) and increased in Tau mice (P = 0.03) relative to WT mice. In contrast, significantly decreased levels were found TauXDrp1+/− mice (P = 0.01) relative to Tau mice.

Similar articles

See all similar articles

Cited by 33 PubMed Central articles

See all "Cited by" articles

Publication types

MeSH terms

Feedback