Tau overexpression impairs neuronal endocytosis by decreasing the GTPase dynamin 1 through the miR-132/MeCP2 pathway

Abstract

Tauopathies are a class of neurodegenerative diseases that are characterized by pathological aggregation of tau protein, which is accompanied by synaptic disorders. However, the role of tau in endocytosis, a fundamental process in synaptic transmission, remains elusive. Here, we report that forced expression of human tau (hTau) in mouse cortical neurons impairs endocytosis by decreasing the level of the GTPase dynamin 1 via disruption of the miR-132-MeCP2 pathway; this process can also be detected in the brains of Alzheimer's patients and hTau mice. Our results provide evidence for a novel role of tau in the regulation of presynaptic function.

Keywords: Tau; dynamin 1; endocytosis; miR-132.

Figure 1

Tau interrupts synaptic endocytosis by decreasing dynamin 1. (a) Primary cortical neurons were infected with lentivirus packed hTau‐EGFP or EGFP at DIV7, and the Transferrin (Tf‐546) uptake experiments were performed at 72 hr later. The red color indicates the internalized Transferrin. Bar = 50 μm. N = 5. (b) The effects of hTau on Tf‐546 endocytosis were detected in several time points. N = 5. (c) The neurons were treated as above, and the mRNA of dynamin 1 (Dnm1), dynamin 3 (Dnm3), clathrin, and Rab5 were detected. N = 5. **p < 0.01, vs. vector. (d) The representative blots of dynamin1, dynamin3, clathrin, and Tau5 and (e) the quantification. N = 5. **p < 0.01, vs. vector. (f) The representative blots of dynamin1 in neurons that treated with different hTau lentivirus dilutions and (g) the quantification. N = 5.*p < 0.05, vs. vector. (h) The representative blots of dynamin1 in the cortex of 12 weeks hTau transgenic mice and their wild‐type and (i) the quantification. N = 6. *p < 0.05, vs. wild‐type. (j) The dynamin1 mRNA level in the cortex of 12 weeks hTau transgenic and age‐matched wild‐type mice. N = 5. *p < 0.05, vs. wild‐type. (k) The representative blots of dynamin1 in AD brain and control brain, and (l) the quantification. N = 5. *p < 0.05, vs. control

Figure 2

MiR‐132/MeCP2 signal is involved in tau‐induced synaptic endocytosis deficits. (a) Neurons were infected with hTau virus or control, the representative blot of MeCP2 was shown and (b) the quantification. (c) mRNA level of MeCP2 in neurons treated above. N = 5. *p < 0.05, vs. vector. (d) The representative blots of MeCP2 in 12 weeks hTau transgenic mice cortex and their wild‐type and (e) the quantification. (f) The mRNA level of MeCP2 from above samples. N = 6. *p < 0.05, vs. wild‐type. (g) The representative blots of MeCP2 in AD brain samples and (h) the quantification. N = 5. ***p < 0.001, vs. con. (i) The levels of different microRNAs in hTau neurons. N = 5. ***p < 0.001, vs. vector. (j) The level of miR132 in the cortex of 12 weeks hTau transgenic mice and the wild‐type. N = 5. ***p < 0.001, vs. wild‐type. (k) The representative blots of dynamin1, MeCP2 in primary cortical neurons transfected with vector, hTau or hTau +miR132 mimics and (l) the quantification. N = 5. *p < 0.05, vs. vector. ^#p < 0.05, vs. hTau neurons. (m) The mRNA level of dynamin1 in the neurons treated as described in k. *p < 0.05, vs. vector. ^#p < 0.05, vs. hTau neurons. (n) Representative images or (o) timeline curve for the effects of miR‐132 on Tf‐546 endocytosis in hTau neurons. Bars = 50 μm. N = 5. *p < 0.05, vs. vector. ^#p < 0.05, vs. hTau neurons