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==S305I Frontotemporal Lobar Degeneration (FTLD) type II tau filament==
<StructureSection load='10ik' size='340' side='right'caption='[[10ik]], [[Resolution|resolution]] 3.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[10ik]] is a 10 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=10IK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=10IK FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 3.2&#8491;</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=10ik FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=10ik OCA], [https://pdbe.org/10ik PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=10ik RCSB], [https://www.ebi.ac.uk/pdbsum/10ik PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=10ik ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/TAU_HUMAN TAU_HUMAN] Note=In Alzheimer disease, the neuronal cytoskeleton in the brain is progressively disrupted and replaced by tangles of paired helical filaments (PHF) and straight filaments, mainly composed of hyperphosphorylated forms of TAU (PHF-TAU or AD P-TAU). O-GlcNAcylation is greatly reduced in Alzheimer disease brain cerebral cortex leading to an increase in TAU/MAPT phosphorylations.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref>   Defects in MAPT are a cause of frontotemporal dementia (FTD) [MIM:[https://omim.org/entry/600274 600274]; also called frontotemporal dementia (FTD), pallido-ponto-nigral degeneration (PPND) or historically termed Pick complex. This form of frontotemporal dementia is characterized by presenile dementia with behavioral changes, deterioration of cognitive capacities and loss of memory. In some cases, parkinsonian symptoms are prominent. Neuropathological changes include frontotemporal atrophy often associated with atrophy of the basal ganglia, substantia nigra, amygdala. In most cases, protein tau deposits are found in glial cells and/or neurons.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref> <ref>PMID:9629852</ref> <ref>PMID:9736786</ref> <ref>PMID:9641683</ref> <ref>PMID:9789048</ref> <ref>PMID:9973279</ref> <ref>PMID:10553987</ref> <ref>PMID:10214944</ref> <ref>PMID:10374757</ref> <ref>PMID:10489057</ref> <ref>PMID:10208578</ref> <ref>PMID:11117541</ref> <ref>PMID:10802785</ref> <ref>PMID:11071507</ref> <ref>PMID:11585254</ref> <ref>PMID:11278002</ref> <ref>PMID:12473774</ref> <ref>PMID:11921059</ref> <ref>PMID:11906000</ref> <ref>PMID:11889249</ref> <ref>PMID:12509859</ref> <ref>PMID:16240366</ref> <ref>PMID:15883319</ref>   Defects in MAPT are a cause of Pick disease of the brain (PIDB) [MIM:[https://omim.org/entry/172700 172700]. It is a rare form of dementia pathologically defined by severe atrophy, neuronal loss and gliosis. It is characterized by the occurrence of tau-positive inclusions, swollen neurons (Pick cells) and argentophilic neuronal inclusions known as Pick bodies that disproportionally affect the frontal and temporal cortical regions. Clinical features include aphasia, apraxia, confusion, anomia, memory loss and personality deterioration.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref> <ref>PMID:10604746</ref> <ref>PMID:11117542</ref> <ref>PMID:11089577</ref> <ref>PMID:11601501</ref> <ref>PMID:11891833</ref>   Note=Defects in MAPT are a cause of corticobasal degeneration (CBD). It is marked by extrapyramidal signs and apraxia and can be associated with memory loss. Neuropathologic features may overlap Alzheimer disease, progressive supranuclear palsy, and Parkinson disease.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref>   Defects in MAPT are a cause of progressive supranuclear palsy type 1 (PSNP1) [MIM:[https://omim.org/entry/601104 601104]; also abbreviated as PSP and also known as Steele-Richardson-Olszewski syndrome. PSNP1 is characterized by akinetic-rigid syndrome, supranuclear gaze palsy, pyramidal tract dysfunction, pseudobulbar signs and cognitive capacities deterioration. Neurofibrillary tangles and gliosis but no amyloid plaques are found in diseased brains. Most cases appear to be sporadic, with a significant association with a common haplotype including the MAPT gene and the flanking regions. Familial cases show an autosomal dominant pattern of transmission with incomplete penetrance; genetic analysis of a few cases showed the occurrence of tau mutations, including a deletion of Asn-613.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref> <ref>PMID:10534245</ref> <ref>PMID:11220749</ref> <ref>PMID:12325083</ref> <ref>PMID:14991829</ref> <ref>PMID:14991828</ref> <ref>PMID:16157753</ref>   Defects in MAPT are a cause of Parkinson-dementia syndrome (PARDE) [MIM:[https://omim.org/entry/260540 260540]. A syndrome characterized by parkinsonism tremor, rigidity, dementia, ophthalmoparesis and pyramidal signs. Neurofibrillary degeneration occurs in the hippocampus, basal ganglia and brainstem nuclei.<ref>PMID:19451179</ref> <ref>PMID:2484340</ref> <ref>PMID:14517953</ref> 
== Function ==
[https://www.uniprot.org/uniprot/TAU_HUMAN TAU_HUMAN] Promotes microtubule assembly and stability, and might be involved in the establishment and maintenance of neuronal polarity. The C-terminus binds axonal microtubules while the N-terminus binds neural plasma membrane components, suggesting that tau functions as a linker protein between both. Axonal polarity is predetermined by TAU/MAPT localization (in the neuronal cell) in the domain of the cell body defined by the centrosome. The short isoforms allow plasticity of the cytoskeleton whereas the longer isoforms may preferentially play a role in its stabilization.<ref>PMID:21985311</ref> 
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== Publication Abstract from PubMed ==
Frontotemporal lobar degeneration with tau inclusions (FTLD-tau) comprise a class of fatal heterogeneous neurodegenerative diseases. Approximately 10% arise from pathogenic MAPT mutations and often cause severe, early-onset disease with pathology that is distinct yet partially overlapping with sporadic cases. Here, we evaluated post-mortem tissue from a patient with FTLD-tau due to MAPT S305I showing neuropathology most consistent with argyrophilic grain disease (AGD), a prevalent limbic tauopathy of aging. Structures determined by cryo-electron microscopy reveal tau filament folds that differ from those found in sporadic AGD or other tauopathies and feature a 4-layer architecture stabilized by the Ile substitution within its core. Comparative structural analysis reveals conserved motifs are shared among AGD, corticobasal degeneration, and MAPT P301T. A well-defined density stacks along a cationic cleft, indicative of a bound RNA-like polyanion or small-molecule. In vitro analysis shows the S305I mutation promotes fibrilization relative to normal tau. These results demonstrate that MAPT S305I stabilizes a distinct aggregation-prone tau fold that likely contributes to disease pathology and heterogeneity beyond its known splicing defects, and underscore potential limitations of using the most pathologically similar genetic form as a model for sporadic FTLD-tau.

Distinct tau filament folds in familial frontotemporal dementia due to the MAPT S305I mutation.,Pan HS, Merz GE, Li AN, Le MQ, Jo H, Quddus A, Yung A, Kormos RC, Melo AA, Ramos EM, Lago AL, Spina S, Grinberg LT, Rosen HJ, Tse E, Gorno-Tempini ML, DeGrado WF, Seeley WW, Southworth DR bioRxiv [Preprint]. 2026 Feb 15:2026.02.12.705620. doi: , 10.64898/2026.02.12.705620. PMID:41726928<ref>PMID:41726928</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Merz GE]]
[[Category: Pan HS]]
[[Category: Southworth DR]]
[[Category: Tse E]]