Implications of Valosin-containing Protein in Promoting Autophagy to Prevent Tau Aggregation

Histone deacetylase's regulates Tau function in Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disease associated with dementia and neuronal impairments in brain. AD is characterized histopathologically by two hallmark lesions: abnormally phosphorylated Tau inside neurons as intracellular NFTs and extracellular accumulation of amyloid β peptide (Aβ). Furthermore, it is unable to clarify the distinction between the brief association between the development and build-up of Aβ and the commencement of illness. Additionally, a number of experimental findings suggest that symptoms related to Aβ may only manifest within the framework of anabatic Tauopathies. Tau, a natively unfolded protein, essentially involved in microtubule binding and assembly. Tau protein consists of truncated segment and the purpose of this truncated fragment is to initiate and promote the conversion of soluble Tau into aggregates. The most common aberrant posttranslational change found in Neuro Fibrillary Tangles is hyperphosphorylation, which is essentially composed of aggregated Tau. Tau phosphorylation and acetylation of Tau protein at the locations controlled by histone deacetylase 6 compete, which modulates Tau function. Considering the potential benefits of targeting HDAC6 in AD, we propose focusing on the role of HDAC6 in regulating Tau functions and the other targets are the therapeutic understanding of AD.

Nuclear Tau accumulation in Alzheimer's disease

Tau is a well-known microtubule-associated protein and is located in the cytoplasm of neurons, which play a crucial role in Alzheimer's diseases. Due to its preferred binding to DNA sequences found in the nucleolus and pericentromeric heterochromatin, Tau has been found within the cell nucleus, where it may be a nucleic acid-associated protein. Tau has the ability to directly interact with nuclear pore complex nucleoporins, influencing both their structural and functional integrity. The interaction between Tau and NUPs highlights a potential mechanism underlying NPC dysfunction in AD pathogenesis. Pathological Tau hinders the import and export of nucleus through RAN mediated cascades. Nuclear Tau aggregates colocalize with membrane less organelles called nuclear speckles, which are involved in pre-mRNA splicing, and modify their dynamics, composition, and structure. Additionally, SRRM2 and other nuclear speckle proteins including MSUT2 and PABPN1 mislocalize to cytosolic Tau aggregates, and causes propagation of Tau aggregates. Research highlights, Extracellular Tau Oligomers induce significant nuclear invagination. They act as a key player in the transformation of healthy neurons into sick neurons in AD. The mechanism behind this phenomenon depends on intracellular Tau and is linked to changes in chromatin structure, nucleocytoplasmic transport, and gene transcription. This review highlights the vital roles of nuclear Tau protein in the context of nuclear pore complex functioning and, modulation of nuclear speckles in Alzheimer's diseases. Addressing these pathways is essential for formulating focused therapeutics intended to alleviate Tau-induced neurodegeneration.

Proteostasis and neurodegeneration: a closer look at autophagy in Alzheimer's disease

Alzheimer's disease (AD) is characterized by the accumulation of misfolded amyloid-beta and tau proteins. Autophagy acts as a proteostasis process to remove protein clumps, although it progressively weakens with aging and AD, thus facilitating the accumulation of toxic proteins and causing neurodegeneration. This review examines the impact of impaired autophagy on the progression of AD disease pathology. Under normal circumstances, autophagy removes abnormal proteins and damaged organelles, but any dysfunction in this process can lead to the exacerbation of amyloid and tau pathology, particularly in AD. There is increasing attention to therapeutic tactics to revitalize autophagy, including reduced caloric intake, autophagy-stimulating drugs, and genetic therapy. However, the translation of these strategies into clinical practice faces several hurdles. In summary, this review integrates the understanding of the intricate role of autophagy dysfunction in Alzheimer's disease progression and reinforces the promising prospects of autophagy as a beneficial target for treatments to modify the course of Alzheimer's disease.

1-L Transcription in Alzheimer's Disease

Alzheimer's disease is a very complex disease and better explanations and models are needed to understand how neurons are affected and microglia are activated. A new model of Alzheimer's disease is presented here, the β-amyloid peptide is considered an important RNA recognition/binding peptide. 1-L transcription revealed compatible sequences with AAUAAA (PAS signal) and UUUC (class III ARE rich in U) in the Aβ peptide, supporting the peptide-RNA regulatory model. When a hypothetical model of fibril selection with the prionic character of amyloid assemblies is added to the peptide-RNA regulatory model, the downregulation of the PI3K-Akt pathway and the upregulation of the PLC-IP3 pathway are well explained. The model explains why neurons are less protected from inflammation and why microglia are activated; why mitochondria are destabilized; why the autophagic flux is destabilized; and why the post-transcriptional attenuation of the axonal signal "noise" is interrupted. For example, the model suggests that Aβ peptide may post-transcriptionally control ELAVL2 (ELAV-like RNA binding protein 2) and DCP2 (decapping mRNA protein 2), which are known to regulate RNA processing, transport, and stability.