O5‐04‐01: Trim46 Knockdown Causes Neuronal Tau Redistribution And Increases Axosomatic Tau Diffusion

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152676/1/alzjjalz2019064852.pd

Soluble pre-fibrillar tau and β-amyloid species emerge in early human Alzheimer’s disease and track disease progression and cognitive decline

Acknowledgments We would like to gratefully acknowledge all donors and their families for the tissue provided for this study. Human tissue samples were supplied by the Brains for Dementia Research programme, jointly funded by Alzheimer’s Research UK, the Alzheimer’s Society and the Medical Research Council, and sourced from the MRC London Neurodegenerative Diseases Brain Bank, the Manchester Brain Bank, the South West Dementia Brain Bank (SWDBB), the Newcastle Brain Tissue Resource and the Oxford Brain Bank. The Newcastle Brain Tissue Resource and Oxford Brain Bank are also supported by the National Institute for Health Research (NIHR) Units. The South West Dementia Brain Bank (SWDBB) receives additional support from BRACE (Bristol Research into Alzheimer’s and Care of the Elderly). Alz-50, CP13, MC-1 and PHF-1 antibodies were gifted from Dr. Peter Davies and brain lystates from BACE1−/−mice were obtained from Prof Mike Ashford. The work presented here was funded by Alzheimer’s Research UK (Grant refs: ARUKPPG2014A-21 and ARUK-NSG2015-1 to BP and DK and NIH/NIA grants NIH/NINDS R01 NS082730 and R01 AG044372 to NK)Peer reviewedPublisher PD

Behavioral and neuropathological characterization over the adult lifespan of the human tau knock-in mouse

Tau is a microtubule-associated protein with a diverse functional repertoire linked to neurodegenerative disease. Recently, a human tau knock-in (MAPT KI) mouse was developed that may overcome many limitations associated with current animal models used to study tau. In MAPT KI mice, the entire murine Mapt gene was replaced with the human MAPT gene under control of the endogenous Mapt promoter. This model represents an ideal in vivo platform to study the function and dysfunction of human tau protein. Accordingly, a detailed understanding of the effects MAPT KI has on structure and function of the CNS is warranted. Here, we provide a detailed behavioral and neuropathological assessment of MAPT KI mice. We compared MAPT KI to wild-type (WT) C57BL/6j mice in behavioral assessments of anxiety, attention, working memory, spatial memory, and motor performance from 6 to 24 months (m) of age. Using immunohistological and biochemical assays, we quantified markers of glia (microglia, astrocytes and oligodendrocytes), synaptic integrity, neuronal integrity and the cytoskeleton. Finally, we quantified levels of total tau, tau isoforms, tau phosphorylation, and tau conformations. MAPT KI mice show normal cognitive and locomotor behavior at all ages, and resilience to mild age-associated locomotor deficits observed in WT mice. Markers of neuronal and synaptic integrity are unchanged in MAPT KI mice with advancing age. Glial markers are largely unchanged in MAPT KI mice, but glial fibrillary acidic protein is increased in the hippocampus of WT and MAPT KI mice at 24 m. MAPT KI mice express all 6 human tau isoforms and levels of tau remain stable throughout adulthood. Hippocampal tau in MAPT KI and WT mice is phosphorylated at serine 396/404 (PHF1) and murine tau in WT animals displays more PHF1 phosphorylation at 6 and 12 m. Lastly, we extended previous reports showing that MAPT KI mice do not display overt pathology. No evidence of other tau phosphorylation residues (AT8, pS422) or abnormal conformations (TNT2 or TOC1) associated with pathogenic tau were detected. The lack of overt pathological changes in MAPT KI mice make this an ideal platform for future investigations into the function and dysfunction of tau protein in vivo

Analysis of isoform-specific tau aggregates suggests a common toxic mechanism involving similar pathological conformations and axonal transport inhibition

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Neurobiology of Aging 47 (2016): 113–126, doi:10.1016/j.neurobiolaging.2016.07.015.Misfolded tau proteins are characteristic of tauopathies, but the isoform composition of tau inclusions varies by tauopathy. Using aggregates of the longest tau isoform (containing 4 microtubule-binding repeats and 4-repeat tau), we recently described a direct mechanism of toxicity that involves exposure of the N-terminal phosphatase-activating domain (PAD) in tau, which triggers a signaling pathway that disrupts axonal transport. However, the impact of aggregation on PAD exposure for other tau isoforms was unexplored. Here, results from immunochemical assays indicate that aggregation-induced increases in PAD exposure and oligomerization are common features among all tau isoforms. The extent of PAD exposure and oligomerization was larger for tau aggregates composed of 4-repeat isoforms compared with those made of 3-repeat isoforms. Most important, aggregates of all isoforms exhibited enough PAD exposure to significantly impair axonal transport in the squid axoplasm. We also show that PAD exposure and oligomerization represent common pathological characteristics in multiple tauopathies. Collectively, these results suggest a mechanism of toxicity common to each tau isoform that likely contributes to degeneration in different tauopathies.This work was supported by NIH grants R01 AG044372 (Nicholas M. Kanaan), R01 NS082730 (Nicholas M. Kanaan and Scott T. Brady), BrightFocus Foundation (A2013364S, Nicholas M. Kanaan), the Jean P. Schultz Biomedical Research Endowment (Nicholas M. Kanaan), the Secchia Family Foundation (Nicholas M. Kanaan) and NS066942A (Gerardo Morfini)

Tau: a signaling hub protein

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mueller, R. L., Combs, B., Alhadidy, M. M., Brady, S. T., Morfini, G. A., & Kanaan, N. M. Tau: a signaling hub protein. Frontiers in Molecular Neuroscience, 14, (2021): 647054, https://doi.org/10.3389/fnmol.2021.647054.Over four decades ago, in vitro experiments showed that tau protein interacts with and stabilizes microtubules in a phosphorylation-dependent manner. This observation fueled the widespread hypotheses that these properties extend to living neurons and that reduced stability of microtubules represents a major disease-driving event induced by pathological forms of tau in Alzheimer’s disease and other tauopathies. Accordingly, most research efforts to date have addressed this protein as a substrate, focusing on evaluating how specific mutations, phosphorylation, and other post-translational modifications impact its microtubule-binding and stabilizing properties. In contrast, fewer efforts were made to illuminate potential mechanisms linking physiological and disease-related forms of tau to the normal and pathological regulation of kinases and phosphatases. Here, we discuss published work indicating that, through interactions with various kinases and phosphatases, tau may normally act as a scaffolding protein to regulate phosphorylation-based signaling pathways. Expanding on this concept, we also review experimental evidence linking disease-related tau species to the misregulation of these pathways. Collectively, the available evidence supports the participation of tau in multiple cellular processes sustaining neuronal and glial function through various mechanisms involving the scaffolding and regulation of selected kinases and phosphatases at discrete subcellular compartments. The notion that the repertoire of tau functions includes a role as a signaling hub should widen our interpretation of experimental results and increase our understanding of tau biology in normal and disease conditions.This work was supported by NIH grants (R01AG067762 and R01AG044372 to NK, R01NS082730 to NK and SB, R01NS118177 and R21NS120126 to GM, R01NS023868 and R01NS041170 to SB), a gift from Neurodegenerative Research Inc. (GM), a Zenith Award from the Alzheimer’s Association (SB), a grant from the Secchia Family Foundation (NK), NIH/National Institute on Aging (NIA) funded Michigan Alzheimer’s Disease Research Center 5P30AG053760 (BC), the Office of the Assistant Secretary of Defense for Health Affairs through the Peer-Reviewed Alzheimer’s Research Program (Award No. W81XWH-20-1-0174 to BC), and an Alzheimer’s Association Research Grant 20-682085 (BC)

Pseudophosphorylation of tau at S422 enhances SDS-stable dimer formation and impairs both anterograde and retrograde fast axonal transport

AbstractIn Alzheimer's disease (AD), tau undergoes numerous modifications, including increased phosphorylation at serine-422 (pS422). In the human brain, pS422 tau protein is found in prodromal AD, correlates well with cognitive decline and neuropil thread pathology, and appears associated with increased oligomer formation and exposure of the N-terminal phosphatase-activating domain (PAD). However, whether S422 phosphorylation contributes to toxic mechanisms associated with disease-related forms of tau remains unknown. Here, we report that S422-pseudophosphorylated tau (S422E) lengthens the nucleation phase of aggregation without altering the extent of aggregation or the types of aggregates formed. When compared to unmodified tau aggregates, the S422E modification significantly increased the amount of SDS-stable tau dimers, despite similar levels of immunoreactivity with an oligomer-selective antibody (TOC1) and another antibody that reports PAD exposure (TNT1). Vesicle motility assays in isolated squid axoplasm further revealed that S422E tau monomers inhibited anterograde, kinesin-1 dependent fast axonal transport (FAT). Unexpectedly, and unlike unmodified tau aggregates, which selectively inhibit anterograde FAT, aggregates composed of S422E tau were found to inhibit both anterograde and retrograde FAT. Highlighting the relevance of these findings to human disease, pS422 tau was found to colocalize with tau oligomers and with a fraction of tau showing increased PAD exposure in the human AD brain. This study identifies novel effects of pS422 on tau biochemical properties, including prolonged nucleation and enhanced dimer formation, which correlate with a distinct inhibitory effect on FAT. Taken together, these findings identify a novel mechanistic basis by which pS422 confers upon tau a toxic effect that may directly contribute to axonal dysfunction in AD and other tauopathies

Heat Shock Protein 70 Prevents both Tau Aggregation and the Inhibitory Effects of Preexisting Tau Aggregates on Fast Axonal Transport

Aggregation and accumulation of the microtubule-associated protein tau are associated with cognitive decline and neuronal degeneration in Alzheimer's disease and other tauopathies. Thus, preventing the transition of tau from a soluble state to insoluble aggregates and/or reversing the toxicity of existing aggregates would represent a reasonable therapeutic strategy for treating these neurodegenerative diseases. Here we demonstrate that molecular chaperones of the heat shock protein 70 (Hsp70) family are potent inhibitors of tau aggregation in vitro, preventing the formation of both mature fibrils and oligomeric intermediates. Remarkably, addition of Hsp70 to a mixture of oligomeric and fibrillar tau aggregates prevents the toxic effect of these tau species on fast axonal transport, a critical process for neuronal function. When incubated with preformed tau aggregates, Hsp70 preferentially associated with oligomeric over fibrillar tau, suggesting that prefibrillar oligomeric tau aggregates play a prominent role in tau toxicity. Taken together, our data provide a novel molecular basis for the protective effect of Hsp70 in tauopathies

Frontotemporal lobar dementia mutant tau impairs axonal transport through a protein phosphatase 1γ-dependent mechanism

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Combs, B., Christensen, K. R., Richards, C., Kneynsberg, A., Mueller, R. L., Morris, S. L., Morfini, G., Brady, S. T., & Kanaan, N. M. Frontotemporal lobar dementia mutant tau impairs axonal transport through a protein phosphatase 1γ-dependent mechanism. Journal of Neuroscience, 41(45), (2021): 9431-9451, https://doi.org/10.1523/JNEUROSCI.1914-20.2021.Pathologic tau modifications are characteristic of Alzheimer's disease and related dementias, but mechanisms of tau toxicity continue to be debated. Inherited mutations in tau cause early onset frontotemporal lobar dementias (FTLD-tau) and are commonly used to model mechanisms of tau toxicity in tauopathies. Previous work in the isolated squid axoplasm model demonstrated that several pathogenic forms of tau inhibit axonal transport through a mechanism involving activation of protein phosphatase 1 (PP1). Here, we determined that P301L and R5L FTLD mutant tau proteins elicit a toxic effect on axonal transport as monomeric proteins. We evaluated interactions of wild-type or mutant tau with specific PP1 isoforms (α, β, and γ) to examine how the interaction contributes to this toxic effect using primary rat hippocampal neurons from both sexes. Pull-down and bioluminescence resonance energy transfer experiments revealed selective interactions of wild-type tau with PP1α and PP1γ isoforms, but not PP1β, which were significantly increased by the P301L tau mutation. The results from proximity ligation assays confirmed the interaction in primary hippocampal neurons. Moreover, expression of FTLD-linked mutant tau in these neurons enhanced levels of active PP1, also increasing the pausing frequency of fluorescently labeled vesicles in both anterograde and retrograde directions. Knockdown of PP1γ, but not PP1α, rescued the cargo-pausing effects of P301L and R5L tau, a result replicated by deleting a phosphatase-activating domain in the amino terminus of P301L tau. These findings support a model of tau toxicity involving aberrant activation of a specific PP1γ-dependent pathway that disrupts axonal transport in neurons.This work was supported by National Institutes of Health (NIH) Grants R01 NS082730 (N.M.K. and S.T.B.), R01 AG044372 (N.M.K.), and R01 AG067762 (N.M.K.); NIH/National Institute on Aging, Michigan Alzheimer's Disease Research Center Grant 5P30AG053760 (B.C.); Office of the Assistant Secretary of Defense for Health Affairs through the Peer Reviewed Alzheimer's Research Program Award W81XWH-20-1-0174 (B.C.); Alzheimer's Association Research Grants 20-682085 (B.C.), R01 NS118177 (G.A.M.), and R21NS120126 (G.A.M.); Zenith Award from the Alzheimer's Association (S.T.B.); Tau Consortium/Rainwater Foundation (S.T.B.); Neurodegenerative Research (G.A.M.); and the Secchia Family Foundation (N.M.K.)

Pathogenic forms of tau inhibit kinesin-dependent axonal transport through a mechanism involving activation of axonal phosphotransferases

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Neuroscience 31 (2011): 9858-9868, doi:10.1523/JNEUROSCI.0560-11.2011.Aggregated filamentous forms of hyperphosphorylated tau (a microtubule-associated protein) represent pathological hallmarks of Alzheimer's disease (AD) and other tauopathies. While axonal transport dysfunction is thought to represent a primary pathogenic factor in AD and other neurodegenerative diseases, the direct molecular link between pathogenic forms of tau and deficits in axonal transport remain unclear. Recently, we demonstrated that filamentous, but not soluble, forms of wild-type tau inhibit anterograde, kinesin-based fast axonal transport (FAT) by activating axonal protein phosphatase 1 (PP1) and glycogen synthase kinase 3 (GSK3), independent of microtubule binding. Here, we demonstrate that amino acids 2–18 of tau, comprising a phosphatase-activating domain (PAD), are necessary and sufficient for activation of this pathway in axoplasms isolated from squid giant axons. Various pathogenic forms of tau displaying increased exposure of PAD inhibited anterograde FAT in squid axoplasm. Importantly, immunohistochemical studies using a novel PAD-specific monoclonal antibody in human postmortem tissue indicated that increased PAD exposure represents an early pathogenic event in AD that closely associates in time with AT8 immunoreactivity, an early marker of pathological tau. We propose a model of pathogenesis in which disease-associated changes in tau conformation lead to increased exposure of PAD, activation of PP1-GSK3, and inhibition of FAT. Results from these studies reveal a novel role for tau in modulating axonal phosphotransferases and provide a molecular basis for a toxic gain-of-function associated with pathogenic forms of tau.This work was supported by NIH Grants T32 AG020506-07 (N.M.K.); AG09466 (L.I.B.); and NS23868, NS23320, and NS41170 (S.T.B.); as well as 2007/2008 MBL Summer Research Fellowships and an ALS/CVS Therapy Alliance grant (G.M.)

Time series spectroscopic and photometric observations of Massive DAV BPM37093

BPM 37093 was the first of only a handful of massive (1.05+/-0.05 Msun; Bergeron et al. 2004; sitta 2000) WD pulsators discovered (Kanaan et al. 1992). These stars are particularly interesting because the exact process of core crystallization (Abrikosov 1960; Kirzhnitz 1960; Salpeter 1961). is poorly constrained by observation, yet adds a 1?2 Gyr uncertainty in the ages of the oldest white dwarf stars observed and hence, in the ages of associations that contain them. Last year, we discovered that ESO uses BPM 37093 as standard star and extracted corresponding spectra from the public archive. The data suggested a variation in the observed hydrogen line profiles that could potentially be due to pulsations, but the measurement did not reach a detection-quality threshold. To further explore this possibility, though, we obtained 4hrs of continuous time series spectroscopy of BPM37093 with Gemini in the Northern Spring of 2014. We present our preliminary results from these data along with those from the accompanying time series photometric observations we gathered from Mt. John (New Zealand), SAAO and PROMPT　to support the Gemini observations.Fil: Atsuko, Nitta. Gemini Observatory; Estados UnidosFil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; BrasilFil: Chené, André Nicholas. Gemini Observatory; Estados UnidosFil: Koester, D.. Universitat Kiel; AlemaniaFil: Provencal, J. L.. University of Delaware; DinamarcaFil: Kleinmani, S. J.. Gemini Observatory; Estados UnidosFil: Sullivan, D. J.. Victoria University of Wellington; Nueva ZelandaFil: Chote, Paul. Victoria University of Wellington; Nueva ZelandaFil: Safeco, Ramotholo. South African Astronomical Observatory; SudáfricaFil: Kanaan, A.. Universidade Federal de Santa Catarina; BrasilFil: Romero, Alejandra Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina. Universidade Federal do Rio Grande do Sul; BrasilFil: Corti, Mariela Alejandra. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Kilic, Mukremin. University of Oklahoma; Estados UnidosFil: Montgomery, M. H.. University of Texas at Austin; Estados UnidosFil: Widget, D. E.. University of Texas at Austin; Estados UnidosEUROWD 14: 19th European White Dwarf WorkshopMontrealCanadáUniversidad de Montrea