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Extracellular Tau levels are influenced by variability in Tau that is associated with tauopathies.

Abstract
Tauopathies are a class of neurodegenerative diseases marked by intracellular aggregates of hyperphosphorylated Tau. These diseases may occur by sporadic mechanisms in which genetic variants represent risk factors for disease, as is the case in Alzheimer disease (AD). In AD, cerebrospinal fluid (CSF) levels of soluble Tau/pTau-181 are higher in cases compared with controls. A subset of frontotemporal dementia (FTD) cases occur by a familial mechanism in which MAPT, the gene that encodes Tau, mutations are dominantly inherited. In symptomatic FTD patients expressing a MAPT mutation, CSF Tau levels are slightly elevated but are significantly lower than in AD patients. We sought to model CSF Tau changes by measuring extracellular Tau in cultured cells. Full-length, monomeric extracellular total Tau and pTau-181 were detectable in human neuroblastoma cells expressing endogenous Tau, in human non-neuronal cells overexpressing wild-type Tau, and in mouse cortical neurons. Tau isoforms influence the rate of Tau release, whereby the N terminus (exons 2/3) and microtubule binding repeat length contribute to Tau release from the cell. Compared with cells overexpressing wild-type Tau, cells overexpressing FTD-associated MAPT mutations produce significantly less extracellular total Tau without altering intracellular total Tau levels. This study demonstrates that cells actively release Tau in the absence of disease or toxicity, and Tau release is modified by changes in the Tau protein that are associated with tauopathies.
AuthorsCeleste M Karch, Amanda T Jeng, Alison M Goate
JournalThe Journal of biological chemistry (J Biol Chem) Vol. 287 Issue 51 Pg. 42751-62 (Dec 14 2012) ISSN: 1083-351X [Electronic] United States
PMID23105105 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
Chemical References
  • Protein Isoforms
  • tau Proteins
Topics
  • Animals
  • Cell Death
  • Cell Line, Tumor
  • Cell Membrane (metabolism)
  • Extracellular Space (metabolism)
  • Frontotemporal Dementia (genetics, metabolism, pathology)
  • HEK293 Cells
  • Humans
  • Mice
  • Microtubules (metabolism)
  • Models, Biological
  • Mutation (genetics)
  • Neurons (metabolism, pathology)
  • Protein Isoforms (metabolism)
  • Secretory Pathway
  • Tauopathies (genetics, metabolism, pathology)
  • tau Proteins (genetics, metabolism)

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