Novel role of TFEB in ADAM10 potentiation and proliferation of neural precursor cells relevant to Alzheimer's disease

项目总结/文摘

PROJECT SUMMARY/ABSTRACT Alzheimer’s disease (AD) is a complex and a highly heterogeneous disease characterized by the deposition of extracellular and intracellular protein deposits. Accumulating data suggest that autophagy-lysosome pathway (ALP) is severely compromised in human AD and activation of ALP is likely to have therapeutic potential for combating neurodegeneration in the AD. It was recently discovered that the transcription factor EB (TFEB), a basic helix-loop-helix transcription factor is a master regulator of the entire ALP. Interestingly, we found the selective loss of nuclear TFEB protein levels in Braak stage-dependent manner in AD patients and that exposure of primary neurons to Aβ oligomers also markedly reduced TFEB immunoreactivity. So far multiple laboratories around the world have repeatedly confirmed the role of TFEB in markedly reducing the protein aggregates in the APP/PS1 as well as tauopathy models using viral vectors for TFEB expression. By generating flag-TFEB transgenic mice for the first time, we showed that TFEB expression significantly reduces hyperphosphorylated tau in the P301S model of tauopathy. Since TFEB has demonstrated promising effects in models of AD, our continued investigations made a surprising discovery that TFEB potentiates the α-secretase ADAM10 expression and sAPPα generation in multiple cell lines and primary neurons. More importantly, here for the first time we show that TFEB expression increases mature ADAM10 protein levels in vivo. Both sAPPα and ADAM10 have many beneficial properties including neuroprotection, neurite extension, prevention of dendritic degeneration, memory enhancement, inhibition of tau phosphorylation and increased trophic support. More importantly, both ADAM10 and sAPPα have shown indisputable role in the proliferation of neural precursor cells (NPCs) and adult neurogenesis. The failure of most AD clinical trials may suggest that mere reductions in Aβ levels may be insufficient to combat AD and that a mechanism to increase additional benefits may be needed. Therefore in this proposal by using our newly generated flag-TFEB mice we want to assess whether TFEB can mitigate the age-associated decline in the number of NPCs and neurogenesis by quantifying BrdU+, NeuN+, DCX+ and their double positives.in the subventricular zone and subgranular zone by measuring spatial memory, motor activity, ADAM10 activity, and sAPPα levels. More crucially, we have also designed experiments to identify the mechanistic basis for TFEB’s role in neurogenesis. We will also test whether TFEB can provide significant protection against excitotoxicity and Aβ oligomers in the organotypic cultures. Using antibodies against ADAM10/sAPPα, we will also address whether ADAM10/sAPPα are responsible for neuroprotection. If positive results are obtained, it may lead to the initiation of a new line of research on TFEB and its pathway on the role of neurogenesis in models of AD and ultimately TFEB may turn out to be excellent therapeutic target for AD.