VPS35 regulates tau phosphorylation and neuropathology in tauopathy.
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ABSTRACT:
SUBMITTER: Vagnozzi AN
PROVIDER: S-EPMC6949432 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Mutations in the vacuolar protein sorting 35 ortholog (VPS35) gene represent a cause of late-onset, autosomal dominant familial Parkinson's disease (PD). A single missense mutation, D620N, is considered pathogenic based upon its segregation with disease in multiple families with PD. At present, the mechanism(s) by which familial VPS35 mutations precipitate neurodegeneration in PD are poorly understood. Here, we employ a germline D620N VPS35 knockin (KI) mouse model of PD to formally establish the age-related pathogenic effects of the D620N mutation at physiological expression levels. Our data demonstrate that a heterozygous or homozygous D620N mutation is sufficient to reproduce key neuropathological hallmarks of PD as indicated by the progressive degeneration of nigrostriatal pathway dopaminergic neurons and widespread axonal pathology. Unexpectedly, endogenous D620N VPS35 expression induces robust tau-positive somatodendritic pathology throughout the brain as indicated by abnormal hyperphosphorylated and conformation-specific tau, which may represent an important and early feature of mutant VPS35-induced neurodegeneration in PD. In contrast, we find no evidence for α-synuclein-positive neuropathology in aged VPS35 KI mice, a hallmark of Lewy body pathology in PD. D620N VPS35 expression also fails to modify the lethal neurodegenerative phenotype of human A53T-α-synuclein transgenic mice. Finally, by crossing VPS35 KI and null mice, our data demonstrate that a single D620N VPS35 allele is sufficient for survival and early maintenance of dopaminergic neurons, indicating that the D620N VPS35 protein is fully functional. Our data raise the tantalizing possibility of a pathogenic interplay between mutant VPS35 and tau for inducing neurodegeneration in PD.
| S-EPMC6431187 | biostudies-literature
Project description:Accumulation of the microtubule-associated protein Tau is linked to neuronal cell death in tauopathies, but how intraneuronal Tau levels are regulated in health and disease remains unclear. Here, we show that conditional inactivation of the trafficking adaptor protein Numb in retinal ganglion cells (RGCs) increases Tau levels and leads to axonal blebbing, which is followed by neuronal cell loss in aged mice. In the TauP301S mouse model of tauopathy, conditional inactivation of Numb in RGCs and spinal motoneurons accelerates neurodegeneration, and loss of Numb in motoneurons also leads to precocious hindlimb paralysis. Conversely, overexpression of the long isoform of Numb (Numb-72) decreases intracellular Tau levels and reduces axonal blebbing in TauP301S RGCs, leading to improved electrical activity in cultured neurons and improves performance in a visually guided behavior test in vivo. These results uncover Numb as a key regulator of intracellular Tau levels and identify Numb-72 as a potential therapeutic factor for tauopathies.
| S-EPMC9581485 | biostudies-literature
Project description:Tau protein is a prominent component of paired helical filaments in Alzheimer's disease (AD) and other tauopathies. While the abnormal phosphorylation of tau on serine and threonine has been well established in the disease process, its phosphorylation on tyrosine has only recently been described. We previously showed that the Src family non-receptor tyrosine kinases (SFKs) Fyn and Src phosphorylate tau on Tyr18 and that phospho-Tyr18-tau was present in AD brain. In this study, we have investigated the appearance of phospho-Tyr18-tau, activated SFK and proliferating cell nuclear antigen (PCNA) during disease progression in a mouse model of human tauopathy.We have used JNPL3, which expresses human tau with P301L mutation, and antibodies specific for phospho-Tyr18-tau (9G3), ser/thr phosphorylated tau (AT8), activated SFK and PCNA. Antibody staining was viewed by either epifluorescence or confocal microscopy.Phospho-Tyr18-tau appeared concurrently with AT8-reactive tau as early as 4 months in JNPL3. Some 9G3-positive cells also contained activated SFKs and PCNA. We also investigated the triple transgenic mouse model of AD and found that unlike the JNPL3 model, the appearance of 9G3 reactivity did not coincide with AT8 in the hippocampus, suggesting that the presence of APP/presenilin influences tau phosphorylation. Also, Thioflavin S-positive plaques were 9G3-negative, suggesting that phospho-Tyr18-tau is absent from the dystrophic neurites of the mouse triple transgenic brain.Our results provide evidence for the association of tyrosine-phosphorylated tau with mechanisms of neuropathogenesis and indicate that SFK activation and cell cycle activation are also involved in JNPL3.
| S-EPMC2939304 | biostudies-literature
Project description:BackgroundGenetic variation at the PTK2B locus encoding the protein Pyk2 influences Alzheimer's disease risk. Neurons express Pyk2 and the protein is required for Amyloid-β (Aβ) peptide driven deficits of synaptic function and memory in mouse models, but Pyk2 deletion has minimal effect on neuro-inflammation. Previous in vitro data suggested that Pyk2 activity might enhance GSK3β-dependent Tau phosphorylation and be required for tauopathy. Here, we examine the influence of Pyk2 on Tau phosphorylation and associated pathology.MethodsThe effect of Pyk2 on Tau phosphorylation was examined in cultured Hek cells through protein over-expression and in iPSC-derived human neurons through pharmacological Pyk2 inhibition. PS19 mice overexpressing the P301S mutant of human Tau were employed as an in vivo model of tauopathy. Phenotypes of PS19 mice with a targeted deletion of Pyk2 expression were compared with PS19 mice with intact Pyk2 expression. Phenotypes examined included Tau phosphorylation, Tau accumulation, synapse loss, gliosis, proteomic profiling and behavior.ResultsOver-expression experiments from Hek293T cells indicated that Pyk2 contributed to Tau phosphorylation, while iPSC-derived human neuronal cultures with endogenous protein levels supported the opposite conclusion. In vivo, multiple phenotypes of PS19 were exacerbated by Pyk2 deletion. In Pyk2-null PS19 mice, Tau phosphorylation and accumulation increased, mouse survival decreased, spatial memory was impaired and hippocampal C1q deposition increased relative to PS19 littermate controls. Proteomic profiles of Pyk2-null mouse brain revealed that several protein kinases known to interact with Tau are regulated by Pyk2. Endogenous Pyk2 suppresses LKB1 and p38 MAPK activity, validating one potential pathway contributing to increased Tau pathology.ConclusionsThe absence of Pyk2 results in greater mutant Tau-dependent phenotypes in PS19 mice, in part via increased LKB1 and MAPK activity. These data suggest that in AD, while Pyk2 activity mediates Aβ-driven deficits, Pyk2 suppresses Tau-related phenotypes.
| S-EPMC9063299 | biostudies-literature
Project description:Distinctive post-translational modifications (PTM) characterize tau inclusions found in tauopathy patients. Using detergent-insoluble tau isolated from Alzheimer's disease (AD-tau) or Progressive Supranuclear Palsy (PSP-tau) patients, we provide insights into whether phosphorylation of critical residues determine templated tau seeding. Our initial data with phosphorylation-ablating mutations (Ser/Thr → Ala) on select sites of P301L tau showed no changes in seeding efficacy by AD-tau or PSP-tau. Interestingly, when specific sites in the R1-R2 repeat domains (Ser262/Thr263/Ser289/Ser305) were mutated to phosphorylation-mimicking amino acid Glu, it substantially reduced the seeding efficiency of AD-tau, but not PSP-tau seeds. The resultant detergent-insoluble tau shows deficient phosphorylation on AT8, AT100, AT180 and PHF1 epitopes, indicating inter-domain cooperativity. We further identify Ser305 as a critical determinant of AD-tau-specific seeding, whereby the phospho-mimicking Ser305Glu tau abrogates seeding by AD-tau but not PSP-tau. This suggests that phosphorylation on Ser305 could be related to the formation of disease-specific tau strains. Our results highlight the existence of a phospho-PTM code in tau seeding and further demonstrate the distinctive nature of this code in 4R tauopathies.
| S-EPMC10612232 | biostudies-literature
Project description:A functional genetic screen using loss-of-function and gain-of-function alleles was performed to identify modifiers of tau-induced neurotoxicity using the 2N/4R (full-length) isoform of wild-type human tau expressed in the fly retina. We previously reported eye pigment mutations, which create dysfunctional lysosomes, as potent modifiers; here, we report 37 additional genes identified from ?1900 genes screened, including the kinases shaggy/GSK-3beta, par-1/MARK, CamKI and Mekk1. Tau acts synergistically with Mekk1 and p38 to down-regulate extracellular regulated kinase activity, with a corresponding decrease in AT8 immunoreactivity (pS202/T205), suggesting that tau can participate in signaling pathways to regulate its own kinases. Modifiers showed poor correlation with tau phosphorylation (using the AT8, 12E8 and AT270 epitopes); moreover, tested suppressors of wild-type tau were equally effective in suppressing toxicity of a phosphorylation-resistant S11A tau construct, demonstrating that changes in tau phosphorylation state are not required to suppress or enhance its toxicity. Genes related to autophagy, the cell cycle, RNA-associated proteins and chromatin-binding proteins constitute a large percentage of identified modifiers. Other functional categories identified include mitochondrial proteins, lipid trafficking, Golgi proteins, kinesins and dynein and the Hsp70/Hsp90-organizing protein (Hop). Network analysis uncovered several other genes highly associated with the functional modifiers, including genes related to the PI3K, Notch, BMP/TGF-? and Hedgehog pathways, and nuclear trafficking. Activity of GSK-3? is strongly upregulated due to TDP-43 expression, and reduced GSK-3? dosage is also a common suppressor of A?42 and TDP-43 toxicity. These findings suggest therapeutic targets other than mitigation of tau phosphorylation.
| S-EPMC3221533 | biostudies-literature
Project description:A clinically and pathologically heterogeneous type of frontotemporal lobar degeneration has abnormal tau pathology in neurons and glia (FTLD-tau). Familial FTLD-tau is usually due to mutations in the tau gene (MAPT). Even FTLD-tau determined by MAPT mutations has clinical and pathologic heterogeneity. Tauopathies are subclassified according to the predominant species of tau that accumulates, with respect to alternative splicing of MAPT, with tau proteins containing three (3R) or four repeats (4R) of ~32 amino acids in the microtubule binding domain. In Pick's disease (PiD), 3R tau predominates, whereas 4R tau is characteristic of corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). Depending upon the specific mutation in MAPT, familial FTLD-tau can have 3R, 4R or a combination of 3R and 4R tau. PiD is the least common FTLD-tau characterized by neuronal Pick bodies in a stereotypic neuroanatomical distribution. PSP and CBD are more common than PiD and have extensive clinical and pathologic overlap, with no distinctive clinical syndrome or biomarker that permits their differentiation. Diagnosis rests upon postmortem examination of the brain and demonstration of globose tangles, oligodendroglial coiled bodies and tufted astrocytes in PSP or threads, pretangles and astrocytic plaques in CBD. The anatomical distribution of tau pathology determines the clinical presentation of PSP and CBD, as well as PiD. The basis for this selective cortical vulnerability in FTLD-tau is unknown.
| S-EPMC3208128 | biostudies-literature
Project description:Deposition of extensively hyperphosphorylated tau in specific brain cells is a clear pathological hallmark in Alzheimer's disease and a number of other neurodegenerative disorders, collectively termed the tauopathies. Furthermore, hyperphosphorylation of tau prevents it from fulfilling its physiological role as a microtubule-stabilizing protein and leaves it increasingly vulnerable to self-assembly, suggestive of a central underlying role of hyperphosphorylation as a contributing factor in the etiology of these diseases. Via in vitro phosphorylation and regulation of kinase activity within cells and acute brain tissue, we reveal that the inflammation associated kinase, protein kinase R (PKR), directly phosphorylates numerous abnormal and disease-modifying residues within tau including Thr181, Ser199/202, Thr231, Ser262, Ser396, Ser404 and Ser409. Similar to disease processes, these PKR-mediated phosphorylations actively displace tau from microtubules in cells. In addition, PKR overexpression and knockdown, respectively, increase and decrease tau protein and mRNA levels in cells. This regulation occurs independent of noncoding transcriptional elements, suggesting an underlying mechanism involving intra-exonic regulation of the tau-encoding microtubule-associated protein tau (MAPT) gene. Finally, acute encephalopathy in wild type mice, induced by intracranial Langat virus infection, results in robust inflammation and PKR upregulation accompanied by abnormally phosphorylated full-length- and truncated tau. These findings indicate that PKR, independent of other kinases and upon acute brain inflammation, is capable of triggering pathological modulation of tau, which, in turn, might form the initial pathologic seed in several tauopathies such as Alzheimer's disease and Chronic traumatic encephalopathy where inflammation is severe.
| S-EPMC8018097 | biostudies-literature
Project description:Transcellular propagation of protein aggregates, or proteopathic seeds, may drive the progression of neurodegenerative diseases in a prion-like manner. In tauopathies such as Alzheimer's disease, this model predicts that tau seeds propagate pathology through the brain via cell-cell transfer in neural networks. The critical role of tau seeding activity is untested, however. It is unknown whether seeding anticipates and correlates with subsequent development of pathology as predicted for a causal agent. One major limitation has been the lack of a robust assay to measure proteopathic seeding activity in biological specimens. We engineered an ultrasensitive, specific, and facile FRET-based flow cytometry biosensor assay based on expression of tau or synuclein fusions to CFP and YFP, and confirmed its sensitivity and specificity to tau (? 300 fM) and synuclein (? 300 pM) fibrils. This assay readily discriminates Alzheimer's disease vs. Huntington's disease and aged control brains. We then carried out a detailed time-course study in P301S tauopathy mice, comparing seeding activity versus histological markers of tau pathology, including MC1, AT8, PG5, and Thioflavin S. We detected robust seeding activity at 1.5 mo, >1 mo before the earliest histopathological stain. Proteopathic tau seeding is thus an early and robust marker of tauopathy, suggesting a proximal role for tau seeds in neurodegeneration.
| S-EPMC4205609 | biostudies-literature
Project description:BACKGROUND:The accumulation of pathological tau is the main component of neurofibrillary tangles and other tau aggregates in several neurodegenerative diseases, referred to as tauopathies. Recently, immunotherapeutic approaches targeting tau have been demonstrated to be beneficial in decreasing tauopathy in animal models. We previously found that passive immunotherapy with anti-tau antibody to human tau or expression of an anti-tau secreted single-chain variable fragment (scFv) in the central nervous system of a mouse model of tauopathy decreased but did not remove all tau-associated pathology. Although these and other studies demonstrate that conventional immunotherapeutic approaches targeting tau can influence tau pathogenesis, the majority of pathological tau remains in the cytosol of cells, not typically accessible to an extracellular antibody. Therefore, we reasoned targeting intracellular tau might be more efficacious in preventing or decreasing tauopathy. METHODS:By utilizing our anti-tau scFv, we generated anti-tau intrabodies for the expression in the cytosol of neurons. To enhance the degradation capacity of conventional intrabodies, we engineered chimeric anti-tau intrabodies fused to ubiquitin harboring distinct mutations that shuttle intracellular tau for either the proteasome or lysosomal mediated degradation. To evaluate the efficacy in delaying or eliminating tauopathy, we expressed our tau degrading intrabodies or controls in human tau transgenic mice by adeno-associated virus prior to overt tau pathology and after tau deposition. RESULTS:Our results demonstrate, the expression of chimeric anti-tau intrabodies significantly reduce tau protein levels in primary neuronal cultures expression human tau relative to a non-modified anti-tau intrabody. We found the expression of engineered tau-degrading intrabodies destined for proteasomal-mediated degradation are more effective in delaying or eliminating tauopathy than a conventional intrabody in aged human tau transgenic mice. CONCLUSION:This study, harnesses the strength of intrabodies that are amendable for targeting specific domains or modifications with the cell-intrinsic mechanisms that regulate protein degradation providing a new immunotherapeutic approach with potentially improved efficacy.
| S-EPMC6805661 | biostudies-literature