-
[show abstract]
[hide abstract]
ABSTRACT: Previously, we reported the characterization of two novel antibodies that react with tau nitrated at tyrosine 197 (Tau-nY197) and tyrosine 394 (Tau-nY394) in Alzheimer's disease (AD). In this report, we examined whether tau nitration at these sites also occurs in corticobasal degeneration (CBD), progressive supranuclear palsy (PSP) and Pick's disease (PiD), three neurodegenerative tauopathies that contain abundant tau deposits within glial and neuronal cell types but lack amyloid deposition. The reactivity of these antibodies was also compared to two previously characterized antibodies Tau-nY18 and Tau-nY29, specific for tau nitrated at tyrosine 18 and tyrosine 29, respectively. In the present experiments, Tau-nY18 did not label the classical pathological lesions of CBD or PSP but did label the neuronal lesions associated with PiD to a limited extent. In contrast, Tau-nY29 revealed some, but not all classes of tau inclusions associated with both CBD and PSP but did label numerous Pick body inclusions in PiD. Tau-nY197 was restricted to the neuropil threads in both CBD and PSP; however, similar to Tau-nY29, extensive Pick body pathology was clearly labeled. Tau-nY394 did not detect any of the lesions associated with these disorders. In contrast, extensive neuronal and glial tau pathology within these diseases was labeled by Tau-Y197, a monoclonal antibody that reacts within the Y-197-containing proline-rich region of the molecule. Based on our Western and IHC experiments, it appears that nitration of tau at tyrosine 29 is a pathological modification that might be associated with neurodegeneration. Collectively, our data suggest that site-specific tau tyrosine nitration events occur in a disease and lesion-specific manner, indicating that nitration appears to be a highly controlled modification in AD and non-AD tauopathies.
Acta Neuropathologica 11/2011; 123(1):119-32. · 9.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Tau is a microtubule-associated protein that forms neurofibrillary tangles (NFTs) in the selective vulnerable long projection neurons of the cholinergic basal forebrain (CBF) in Alzheimer's disease (AD). Although CBF neurodegeneration correlates with cognitive decline during AD progression, little is known about the temporal changes of tau accumulation in this region. We investigated tau posttranslational modifications during NFT evolution within the CBF neurons of the nucleus basalis (NB) using tissue from subjects with no cognitive impairment, mild cognitive impairment, and AD. The pS422 antibody was used as an early tau pathology marker that labels tau phosphorylated at Ser422; the TauC3 antibody was used to detect later stage tau pathology. Stereologic evaluation of NB tissue immunostained for pS422 and TauC3 revealed an increase in neurons expressing these tau epitopes during disease progression. We also investigated the occurrence of pretangle tau events within cholinergic NB neurons by dual staining for the cholinergic cell marker, p75(NTR), which displays a phenotypic down-regulation within CBF perikarya in AD. As pS422+ neurons increased in number, p75(NTR)+ neurons decreased, and these changes correlated with both AD neuropathology and cognitive decline. Also, NFTs developed slower in the CBF compared with previously examined cortical regions. Taken together, these results suggest that changes in cognition are associated with pretangle events within NB cholinergic neurons before frank NFT deposition.
American Journal Of Pathology 09/2011; 179(5):2533-50. · 4.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We describe an instrument to record x-ray diffraction patterns from diseased regions of human brain tissue by combining an in-line visible light fluorescence microscope with an x-ray diffraction microprobe. We use thiazine red fluorescence to specifically label and detect the filamentous tau protein pathology associated with Pick's disease, as several labs have done previously. We demonstrate that thiazine red-enhanced regions within the tissue show periodic structure in x-ray diffraction that is not observed in healthy tissue. One observed periodicity (4.2 Å) is characteristic of cross-beta sheet structure, consistent with previous results from powder diffraction studies performed on purified, dried tau protein.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 09/2011; 649(1):184-187. · 1.21 Impact Factor
-
Kristina R. Patterson,
Christine Remmers,
Yifan Fu,
Sarah Brooker,
Nicholas M. Kanaan, Laurel Vana,
Sarah Ward,
Juan F. Reyes,
Keith Philibert,
Marc J. Glucksman,
Lester I. Binder
[show abstract]
[hide abstract]
ABSTRACT: Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark
of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the
formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To
determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular
interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers
self-associate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated
a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity
to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions
such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken
as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar
Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration.
Journal of Biological Chemistry 06/2011; 286(26):23063-23076. · 4.77 Impact Factor
-
Kristina R Patterson,
Christine Remmers,
Yifan Fu,
Sarah Brooker,
Nicholas M Kanaan, Laurel Vana,
Sarah Ward,
Juan F Reyes,
Keith Philibert,
Marc J Glucksman,
Lester I Binder
[show abstract]
[hide abstract]
ABSTRACT: Neurofibrillary tangles, composed of insoluble aggregates of the microtubule-associated protein Tau, are a pathological hallmark of Alzheimer disease (AD) and other tauopathies. However, recent evidence indicates that neuronal dysfunction precedes the formation of these insoluble fibrillar deposits, suggesting that earlier prefibrillar Tau aggregates may be neurotoxic. To determine the composition of these aggregates, we have employed a photochemical cross-linking technique to examine intermolecular interactions of full-length Tau in vitro. Using this method, we demonstrate that dimerization is an early event in the Tau aggregation process and that these dimers self-associate to form larger oligomeric aggregates. Moreover, using these stabilized Tau aggregates as immunogens, we generated a monoclonal antibody that selectively recognizes Tau dimers and higher order oligomeric aggregates but shows little reactivity to Tau filaments in vitro. Immunostaining indicates that these dimers/oligomers are markedly elevated in AD, appearing in early pathological inclusions such as neuropil threads and pretangle neurons as well as colocalizing with other early markers of Tau pathogenesis. Taken as a whole, the work presented herein demonstrates the existence of alternative Tau aggregates that precede formation of fibrillar Tau pathologies and raises the possibility that these hierarchical oligomeric forms of Tau may contribute to neurodegeneration.
Journal of Biological Chemistry 05/2011; 286(26):23063-76. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A substantial body of evidence suggests that nitrative injury contributes to neurodegeneration in Alzheimer's disease (AD) and other neurodegenerative disorders. Previously, we showed in vitro that within the tau protein the N-terminal tyrosine residues (Y18 and Y29) are more susceptible to nitrative modifications than other tyrosine sites (Y197 and Y394). Using site-specific antibodies to nitrated tau at Y18 and Y29, we identified tau nitrated in both glial (Y18) and neuronal (Y29) tau pathologies. In this study, we report the characterization of two novel monoclonal antibodies, Tau-nY197 and Tau-nY394, recognizing tau nitrated at Y197 and Y394, respectively. By Western blot analysis, Tau-nY197 labeled soluble tau and insoluble paired helical filament proteins (PHF-tau) nitrated at Y197 from control and AD brain samples. Tau-nY394 failed to label soluble tau isolated from control or severe AD samples, but labeled insoluble PHF-tau to a limited extent. Immunohistochemical analysis using Tau-nY197 revealed the hallmark tau pathology associated with AD; Tau-nY394 did not detect any pathological lesions characteristic of the disorder. These data suggest that a subset of the hallmark pathological inclusions of AD contain tau nitrated at Y197. However, nitration at Y197 was also identified in soluble tau from all control samples, including those at Braak stage 0, suggesting that nitration at this site in the proline-rich region of tau may have normal biological functions in the human brain.
American Journal Of Pathology 05/2011; 178(5):2275-85. · 4.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Tau undergoes numerous posttranslational modifications during the progression of Alzheimer's disease (AD). Some of these changes accelerate tau aggregation, while others are inhibitory. AD-associated inflammation is thought to create oxygen and nitrogen radicals such as peroxynitrite (PN). In vitro, PN can nitrate many proteins, including tau. We have previously demonstrated that tau's ability to form filaments is profoundly affected by treatment with PN and have attributed this inhibition to tyrosine nitration. However, PN is highly reactive and unstable leading to oxidative amino acid modifications through its free radical byproducts. To test whether PN can modify other amino acids in tau via oxidative modifications, a mutant form of the tau protein lacking all tyrosines (5XY → F) was constructed. 5XY → F tau readily forms filaments; however, like wild-type tau the extent of polymerization was greatly reduced following PN treatment. Since 5XY → F tau cannot be nitrated, it was clear that nonnitrative modifications are generated by PN treatment and that these modifications change tau filament formation. Mass spectrometry was used to identify these oxidative alterations in wild-type tau and 5XY → F tau. PN-treated wild-type tau and 5XY → F tau consistently displayed lysine formylation throughout tau in a nonsequence-specific distribution. Lysine formylation likely results from reactive free radical exposure caused by PN treatment. Therefore, our results indicate that PN treatment of proteins in vitro cannot be used to study protein nitration as it likely induces numerous other random oxidative modifications clouding the interpretations of any functional consequences of tyrosine nitration.
Biochemistry 02/2011; 50(7):1203-12. · 3.42 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The age-related pathological cascade underlying intraneuronal tau formation in 3xTg-AD mice, which harbor the human APP(Swe), PS1(M126V) , and Tau(P301L) gene mutations, remains unclear. At 3 weeks of age, AT180, Alz50, MC1, AT8, and PHF-1 intraneuronal immunoreactivity appeared in the amygdala and hippocampus and at later ages in the cortex of 3xTg-AD mice. AT8 and PHF-1 staining was fixation dependent in young mutant mice. 6E10 staining was seen at all ages. Fluorescent immunomicroscopy revealed CA1 neurons dual stained for 6E10 and Alz50 and single Alz50 immunoreactive neurons in the subiculum at 3 weeks and continuing to 20 months. Although electron microscopy confirmed intraneuronal cytoplasmic Alz50, AT8, and 6E10 reaction product in younger 3xTg-AD mice, straight filaments appeared at 23 months of age in female mice. The present data suggest that other age-related biochemical mechanisms in addition to early intraneuronal accumulation of 6E10 and tau underlie the formation of tau filaments in 3xTg-AD mice.
International journal of Alzheimer's disease. 01/2010; 2010.
