1
|
Jimenez-Harrison D, Huseby CJ, Hoffman CN, Sher S, Snyder D, Seal B, Yuan C, Fu H, Wysocki V, Giorgini F, Kuret J. DJ-1 Molecular Chaperone Activity Depresses Tau Aggregation Propensity through Interaction with Monomers. Biochemistry 2023; 62:976-988. [PMID: 36813261 PMCID: PMC9997487 DOI: 10.1021/acs.biochem.2c00581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 01/19/2023] [Indexed: 02/24/2023]
Abstract
Tau aggregate-bearing lesions are pathological markers and potential mediators of tauopathic neurodegenerative diseases, including Alzheimer's disease. The molecular chaperone DJ-1 colocalizes with tau pathology in these disorders, but it has been unclear what functional link exists between them. In this study, we examined the consequences of tau/DJ-1 interaction as isolated proteins in vitro. When added to full-length 2N4R tau under aggregation-promoting conditions, DJ-1 inhibited both the rate and extent of filament formation in a concentration-dependent manner. Inhibitory activity was low affinity, did not require ATP, and was not affected by substituting oxidation incompetent missense mutation C106A for wild-type DJ-1. In contrast, missense mutations previously linked to familial Parkinson's disease and loss of α-synuclein chaperone activity, M26I and E64D, displayed diminished tau chaperone activity relative to wild-type DJ-1. Although DJ-1 directly bound the isolated microtubule-binding repeat region of tau protein, exposure of preformed tau seeds to DJ-1 did not diminish seeding activity in a biosensor cell model. These data reveal DJ-1 to be a holdase chaperone capable of engaging tau as a client in addition to α-synuclein. Our findings support a role for DJ-1 as part of an endogenous defense against the aggregation of these intrinsically disordered proteins.
Collapse
Affiliation(s)
- Daniela Jimenez-Harrison
- Medical
Scientist Training Program, The Ohio State
University, Columbus, Ohio 43210, United States
| | - Carol J. Huseby
- Department
of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, Ohio 43210, United States
| | - Claire N. Hoffman
- Department
of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, Ohio 43210, United States
| | - Steven Sher
- Medical
Scientist Training Program, The Ohio State
University, Columbus, Ohio 43210, United States
| | - Dalton Snyder
- Department
of Chemistry and Biochemistry, The Ohio
State University College of Medicine, Columbus, Ohio 43210, United States
| | - Brayden Seal
- Department
of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, Ohio 43210, United States
| | - Chunhua Yuan
- Campus
Chemical Instrument Center, The Ohio State
University College of Medicine, Columbus, Ohio 43210, United States
| | - Hongjun Fu
- Department
of Neuroscience, The Ohio State University
College of Medicine, Columbus, Ohio 43210, United States
| | - Vicki Wysocki
- Department
of Chemistry and Biochemistry, The Ohio
State University College of Medicine, Columbus, Ohio 43210, United States
| | - Flaviano Giorgini
- Department
of Genetics and Genome Biology, University
of Leicester, Leicester LE1 7RH, United
Kingdom
| | - Jeff Kuret
- Department
of Biological Chemistry and Pharmacology, The Ohio State University College of Medicine, Columbus, Ohio 43210, United States
| |
Collapse
|
2
|
Prokopovich DV, Whittaker JW, Muthee MM, Ahmed A, Larini L. Impact of Phosphorylation and Pseudophosphorylation on the Early Stages of Aggregation of the Microtubule-Associated Protein Tau. J Phys Chem B 2017; 121:2095-2103. [PMID: 28218850 DOI: 10.1021/acs.jpcb.7b00194] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The microtubule-associated protein tau regulates the stability of microtubules within neurons in the central nervous system. In turn, microtubules are responsible for the remodeling of the cytoskeleton that ultimately leads to the formation or pruning of new connections among neurons. As a consequence, dysfunction of tau is associated with many forms of dementia as well as Alzheimer's disease. In the brain, tau activity is regulated by its phosphorylation state. Phosphorylation is a post-translational modification of proteins that adds a phosphate group to the side chain of an amino acid. Phosphorylation at key locations in the tau sequence leads to a higher or lower affinity for microtubules. In Alzheimer's disease, tau is present in an abnormal phosphorylation state. However, studying the effect of phosphorylation experimentally has been extremely challenging as there is no viable way of exactly selecting the location and the number of phosphorylated sites. For this reason, researchers have turned to pseudophosphorylation. In this technique, actual phosphorylation is mimicked by mutating the selected amino acid into glutamate or aspartate. Whether this methodology is equivalent to actual phosphorylation is still open to debate. In this study, we will show that phosphorylation and pseudophosphorylation are not exactly equivalent. Although for larger aggregates the two techniques lead to similar structures, the kinetics of the process may be altered. In addition, very little is known about the impact that this may have on the early stages of aggregation, such as nucleation and conformational rearrangement. In this study, we show that the two methods may produce a similar ensemble of conformations, even though the kinetic and chemical details that lead to it are quite different.
Collapse
Affiliation(s)
- Dmitriy V Prokopovich
- Department of Physics and ‡Center for Computational and Integrative Biology, Rutgers University-Camden , Camden, New Jersey 08102, United States
| | - John W Whittaker
- Department of Physics and ‡Center for Computational and Integrative Biology, Rutgers University-Camden , Camden, New Jersey 08102, United States
| | - Micaiah M Muthee
- Department of Physics and ‡Center for Computational and Integrative Biology, Rutgers University-Camden , Camden, New Jersey 08102, United States
| | - Azka Ahmed
- Department of Physics and ‡Center for Computational and Integrative Biology, Rutgers University-Camden , Camden, New Jersey 08102, United States
| | - Luca Larini
- Department of Physics and ‡Center for Computational and Integrative Biology, Rutgers University-Camden , Camden, New Jersey 08102, United States
| |
Collapse
|
3
|
Tiernan CT, Combs B, Cox K, Morfini G, Brady ST, Counts SE, Kanaan NM. Pseudophosphorylation of tau at S422 enhances SDS-stable dimer formation and impairs both anterograde and retrograde fast axonal transport. Exp Neurol 2016; 283:318-29. [PMID: 27373205 PMCID: PMC4992631 DOI: 10.1016/j.expneurol.2016.06.030] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 06/22/2016] [Accepted: 06/28/2016] [Indexed: 12/17/2022]
Abstract
In 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.
Collapse
Affiliation(s)
- Chelsea T Tiernan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Benjamin Combs
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Kristine Cox
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA
| | - Gerardo Morfini
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, IL 60612, USA
| | - Scott T Brady
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, IL 60612, USA
| | - Scott E Counts
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Department of Family Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA; Hauenstein Neuroscience Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI 49503, USA
| | - Nicholas M Kanaan
- Department of Translational Science and Molecular Medicine, Michigan State University, Grand Rapids, MI 49503, USA; Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA; Hauenstein Neuroscience Center, Mercy Health Saint Mary's Hospital, Grand Rapids, MI 49503, USA.
| |
Collapse
|
4
|
Abstract
Conversion of monomeric tau protein into filamentous aggregates is a defining event in the pathogenesis of Alzheimer's disease. To gain insight into disease pathogenesis, the mechanisms that trigger and mediate tau aggregation are under intense investigation. Characterization efforts have relied primarily on recombinant tau protein preparations and high-throughput solution-based detection methods such as thioflavin-dye fluorescence and laser-light-scattering spectroscopies. Transmission electron microscopy (TEM) is a static imaging tool that complements these approaches by detecting individual tau filaments at nanometer resolution. In doing so, it can provide unique insight into the quality, quantity, and composition of synthetic tau filament populations. Here we describe protocols for analysis of tau filament populations by TEM for purposes of dissecting aggregation mechanism.
Collapse
Affiliation(s)
- Carol J Huseby
- Department of Molecular and Cellular Biochemistry, Interdisciplinary Biophysics Graduate Program, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Jeff Kuret
- Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, 108 Rightmire Hall, 1060 Carmack Road, Columbus, OH, 43210, USA.
| |
Collapse
|
5
|
Lysine methylation is an endogenous post-translational modification of tau protein in human brain and a modulator of aggregation propensity. Biochem J 2014; 462:77-88. [PMID: 24869773 DOI: 10.1042/bj20140372] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In Alzheimer's disease, the microtubule-associated protein tau dissociates from the neuronal cytoskeleton and aggregates to form cytoplasmic inclusions. Although hyperphosphorylation of tau serine and threonine residues is an established trigger of tau misfunction and aggregation, tau modifications extend to lysine residues as well, raising the possibility that different modification signatures depress or promote aggregation propensity depending on site occupancy. To identify lysine residue modifications associated with normal tau function, soluble tau proteins isolated from four cognitively normal human brains were characterized by MS methods. The major detectable lysine modification was found to be methylation, which appeared in the form of mono- and di-methyl lysine residues distributed among at least 11 sites. Unlike tau phosphorylation sites, the frequency of lysine methylation was highest in the microtubule-binding repeat region that mediates both microtubule binding and homotypic interactions. When purified recombinant human tau was modified in vitro through reductive methylation, its ability to promote tubulin polymerization was retained, whereas its aggregation propensity was greatly attenuated at both nucleation and extension steps. These data establish lysine methylation as part of the normal tau post-translational modification signature in human brain, and suggest that it can function in part to protect against pathological tau aggregation.
Collapse
|
6
|
D'Alton S, Lewis J. Therapeutic and diagnostic challenges for frontotemporal dementia. Front Aging Neurosci 2014; 6:204. [PMID: 25191265 PMCID: PMC4137452 DOI: 10.3389/fnagi.2014.00204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 07/25/2014] [Indexed: 12/12/2022] Open
Abstract
In the search for therapeutic modifiers, frontotemporal dementia (FTD) has traditionally been overshadowed by other conditions such as Alzheimer's disease (AD). A clinically and pathologically diverse condition, FTD has been galvanized by a number of recent discoveries such as novel genetic variants in familial and sporadic forms of disease and the identification of TAR DNA binding protein of 43 kDa (TDP-43) as the defining constituent of inclusions in more than half of cases. In combination with an ever-expanding knowledge of the function and dysfunction of tau-a protein which is pathologically aggregated in the majority of the remaining cases-there exists a greater understanding of FTD than ever before. These advances may indicate potential approaches for the development of hypothetical therapeutics, but FTD remains highly complex and the roles of tau and TDP-43 in neurodegeneration are still wholly unclear. Here the challenges facing potential therapeutic strategies are discussed, which include sufficiently accurate disease diagnosis and sophisticated technology to deliver effective therapies.
Collapse
Affiliation(s)
- Simon D'Alton
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, College of Medicine, University of Florida Gainesville, FL, USA
| | - Jada Lewis
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, College of Medicine, University of Florida Gainesville, FL, USA
| |
Collapse
|
7
|
Jia SH, Parodo J, Charbonney E, Tsang JLY, Jia SY, Rotstein OD, Kapus A, Marshall JC. Activated neutrophils induce epithelial cell apoptosis through oxidant-dependent tyrosine dephosphorylation of caspase-8. THE AMERICAN JOURNAL OF PATHOLOGY 2014; 184:1030-1040. [PMID: 24589337 DOI: 10.1016/j.ajpath.2013.12.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 11/19/2013] [Accepted: 12/16/2013] [Indexed: 01/12/2023]
Abstract
Activated neutrophils can injure host cells through direct effects of oxidants on membrane phospholipids, but an ability to induce apoptotic cell death has not previously been reported. We show that neutrophils activated in vivo in patients who have sustained multiple trauma or in vitro by exposure to bacterial lipopolysaccharide promote epithelial cell apoptosis through SHP-1-mediated dephosphorylation of epithelial cell caspase-8. Epithelial cell apoptosis induced by circulating neutrophils from patients who had sustained serious injury depended on the generation of neutrophil-derived reactive oxygen intermediates and was blocked by inhibition of NADPH oxidase or restoration of intracellular glutathione. Caspase-8 was constitutively tyrosine phosphorylated in a panel of resting epithelial cells, but underwent SHP-1-dependent dephosphorylation in response to hydrogen peroxide, activated neutrophils, or inhibition of Src kinases. Cells transfected with a mutant caspase-8 in which tyrosine residues at Tyr397 or Tyr465 are replaced by nonphosphorylatable phenylalanine underwent accelerated apoptosis, whereas either mutation of these residues to phosphomimetic glutamic acid or transfection with the Src kinases Lyn or c-Src inhibited hydrogen peroxide-induced apoptosis. Exposure to either hydrogen peroxide or lipopolysaccharide-stimulated neutrophils increased phosphorylation and activity of the phosphatase SHP-1, increased activity of caspases 8 and 3, and accelerated epithelial cell apoptosis. These observations reveal a novel mechanism for neutrophil-mediated tissue injury through oxidant-dependent, SHP-1-mediated dephosphorylation of caspase-8 resulting in enhanced epithelial cell apoptosis.
Collapse
Affiliation(s)
- Song Hui Jia
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada
| | - Jean Parodo
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada
| | - Emmanuel Charbonney
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada; Department of Critical Care Medicine, St. Michael's Hospital, Tortonto, Ontario, Canada
| | - Jennifer L Y Tsang
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada; Department of Critical Care Medicine, St. Michael's Hospital, Tortonto, Ontario, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Sang Yang Jia
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada
| | - Ori D Rotstein
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada; Department of Surgery, St. Michael's Hospital, Tortonto, Ontario, Canada
| | - Andras Kapus
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada; Department of Surgery, St. Michael's Hospital, Tortonto, Ontario, Canada
| | - John C Marshall
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, Tortonto, Ontario, Canada; Department of Critical Care Medicine, St. Michael's Hospital, Tortonto, Ontario, Canada; Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Ontario, Canada; Department of Surgery, St. Michael's Hospital, Tortonto, Ontario, Canada.
| |
Collapse
|
8
|
Yuzwa SA, Cheung AH, Okon M, McIntosh LP, Vocadlo DJ. O-GlcNAc modification of tau directly inhibits its aggregation without perturbing the conformational properties of tau monomers. J Mol Biol 2014; 426:1736-52. [PMID: 24444746 DOI: 10.1016/j.jmb.2014.01.004] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/11/2013] [Accepted: 01/14/2014] [Indexed: 11/29/2022]
Abstract
The aggregation of the microtubule-associated protein tau into paired helical filaments to form neurofibrillary tangles constitutes one of the pathological hallmarks of Alzheimer's disease. Tau is post-translationally modified by the addition of N-acetyl-D-glucosamine O-linked to several serine and threonine residues (O-GlcNAc). Previously, increased O-GlcNAcylation of tau has been shown to block the accumulation of tau aggregates within a tauopathy mouse model. Here we show that O-GlcNAc modification of full-length human tau impairs the rate and extent of its heparin-induced aggregation without perturbing its activity toward microtubule polymerization. O-GlcNAcylation, however, does not impact the "global-fold" of tau as measured by a Förster resonance energy transfer assay. Similarly, nuclear magnetic resonance studies demonstrated that O-GlcNAcylation only minimally perturbs the local structural and dynamic features of a tau fragment (residues 353-408) spanning the last microtubule binding repeat to the major GlcNAc-acceptor Ser400. These data indicate that the inhibitory effects of O-GlcNAc on tau aggregation may result from enhanced monomer solubility or the destabilization of fibrils or soluble aggregates, rather than by altering the conformational properties of the monomeric protein. This work further underscores the potential of targeting the O-GlcNAc pathway for potential Alzheimer's disease therapeutics.
Collapse
Affiliation(s)
- Scott A Yuzwa
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6; Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
| | - Adrienne H Cheung
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and the Michael Smith Laboratories, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
| | - Mark Okon
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and the Michael Smith Laboratories, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
| | - Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and the Michael Smith Laboratories, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
| | - David J Vocadlo
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6; Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6.
| |
Collapse
|
9
|
Schafer KN, Cisek K, Huseby CJ, Chang E, Kuret J. Structural determinants of Tau aggregation inhibitor potency. J Biol Chem 2013; 288:32599-32611. [PMID: 24072703 DOI: 10.1074/jbc.m113.503474] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Small-molecule Tau aggregation inhibitors are under investigation as potential therapeutic agents against Alzheimer disease. Many such inhibitors have been identified in vitro, but their potency-driving features, and their molecular targets in the Tau aggregation pathway, have resisted identification. Previously we proposed ligand polarizability, a measure of electron delocalization, as a candidate descriptor of inhibitor potency. Here we tested this hypothesis by correlating the ground state polarizabilities of cyanine, phenothiazine, and arylmethine derivatives calculated using ab initio quantum methods with inhibitory potency values determined in the presence of octadecyl sulfate inducer under reducing conditions. A series of rhodanine analogs was analyzed as well using potency values disclosed in the literature. Results showed that polarizability and inhibitory potency directly correlated within all four series. To identify putative binding targets, representative members of the four chemotypes were added to aggregation reactions, where they were found to stabilize soluble, but SDS-resistant Tau species at the expense of filamentous aggregates. Using SDS resistance as a secondary assay, and a library of Tau deletion and missense mutants as targets, interaction with cyanine was localized to the microtubule binding repeat region. Moreover, the SDS-resistant phenotype was completely dependent on the presence of octadecyl sulfate inducer, but not intact PHF6/PH6* hexapeptide motifs, indicating that cyanine interacted with a species in the aggregation pathway prior to nucleus formation. Together the data suggest that flat, highly polarizable ligands inhibit Tau aggregation by interacting with folded species in the aggregation pathway and driving their assembly into soluble but highly stable Tau oligomers.
Collapse
Affiliation(s)
- Kelsey N Schafer
- From the Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Katryna Cisek
- From the Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Carol J Huseby
- From the Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Edward Chang
- From the Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210
| | - Jeff Kuret
- From the Department of Molecular and Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210.
| |
Collapse
|
10
|
Zhong Q, Congdon EE, Nagaraja HN, Kuret J. Tau isoform composition influences rate and extent of filament formation. J Biol Chem 2012; 287:20711-9. [PMID: 22539343 DOI: 10.1074/jbc.m112.364067] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The risk of developing tauopathic neurodegenerative disease depends in part on the levels and composition of six naturally occurring Tau isoforms in human brain. These proteins, which form filamentous aggregates in disease, vary only by the presence or absence of three inserts encoded by alternatively spliced exons 2, 3, and 10 of the Tau gene (MAPT). To determine the contribution of alternatively spliced segments to Tau aggregation propensity, the aggregation kinetics of six unmodified, recombinant human Tau isoforms were examined in vitro using electron microscopy assay methods. Aggregation propensity was then compared at the level of elementary rate constants for nucleation and extension phases. We found that all three alternatively spliced segments modulated Tau aggregation but through differing kinetic mechanisms that could synergize or compete depending on sequence context. Overall, segments encoded by exons 2 and 10 promoted aggregation, whereas the segment encoded by exon 3 depressed it with its efficacy dependent on the presence or absence of a fourth microtubule binding repeat. In general, aggregation propensity correlated with genetic risk reported for multiple tauopathies, implicating aggregation as one candidate mechanism rationalizing the correlation between Tau expression patterns and disease.
Collapse
Affiliation(s)
- Qi Zhong
- Department of Molecular & Cellular Biochemistry, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | | | | | | |
Collapse
|
11
|
Combs B, Voss K, Gamblin TC. Pseudohyperphosphorylation has differential effects on polymerization and function of tau isoforms. Biochemistry 2011; 50:9446-56. [PMID: 21942206 DOI: 10.1021/bi2010569] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The microtubule-associated protein tau exists as six isoforms created through the splicing of the second, third, and tenth exons. The isoforms are classified by their number of N-terminal exons (0N, 1N, or 2N) and by their number of microtubule-binding repeat regions (3R or 4R). Hyperphosphorylated isoforms accumulate in insoluble aggregates in Alzheimer's disease and other tauopathies. These neurodegenerative diseases can be categorized based on the isoform content of the aggregates they contain. Hyperphosphorylated tau has the general characteristics of an upward electrophoretic shift, decreased microtubule binding, and an association with aggregation. Previously we have shown that a combination of seven pseudophosphorylation mutations at sites phosphorylated by GSK-3β, referred to as 7-Phos, induced several of these characteristics in full-length 2N4R tau and led to the formation of fewer but longer filaments. We sought to determine whether the same phosphorylation pattern could cause differential effects in the other tau isoforms, possibly through varied conformational effects. Using in vitro techniques, we examined the electrophoretic mobility, aggregation properties, and microtubule stabilization of all isoforms and their pseudophosphorylated counterparts. We found that pseudophosphorylation affected each isoform, but in several cases certain isoforms were affected more than others. These results suggest that hyperphosphorylation of tau isoforms could play a major role in determining the isoform composition of tau aggregates in disease.
Collapse
Affiliation(s)
- Benjamin Combs
- Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, United States
| | | | | |
Collapse
|
12
|
Finding order within disorder: elucidating the structure of proteins associated with neurodegenerative disease. Future Med Chem 2011; 1:467-82. [PMID: 21426127 DOI: 10.4155/fmc.09.40] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A number of neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, involve the formation of protein aggregates. The primary constituent of these aggregates belongs to a unique class of heteropolymers known as intrinsically disordered proteins (IDPs). While many proteins fold to a unique conformation that is determined by their amino acid sequence, IDPs do not adopt a single well-defined conformation in solution. Instead, they populate a heterogeneous set of conformers under physiological conditions. Despite this intrinsic propensity for disorder, a number of these proteins can form ordered aggregates both in vitro and in vivo. As the formation of these aggregates may play an important role in disease pathogenesis, a detailed structural characterization of these proteins and their mechanism of aggregation is of critical importance. However, new methods are needed to understand the diversity of structures that make up the unfolded ensemble of these systems. In this review, we discuss recent advances in the structural analysis and modeling of IDPs involved in neurodegenerative diseases. While there are challenges in both the experimental characterization and the modeling of such proteins, a comprehensive understanding of the structure of IDPs will likely facilitate the development of effective therapies for a number of neurodegenerative diseases.
Collapse
|
13
|
Chang E, Kim S, Schafer KN, Kuret J. Pseudophosphorylation of tau protein directly modulates its aggregation kinetics. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1814:388-95. [PMID: 20974297 DOI: 10.1016/j.bbapap.2010.10.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/11/2010] [Accepted: 10/15/2010] [Indexed: 11/27/2022]
Abstract
Hyperphosphorylation of tau protein is associated with neurofibrillary lesion formation in Alzheimer's disease and other tauopathic neurodegenerative diseases. It fosters lesion formation by increasing the concentration of free tau available for aggregation and by directly modulating the tau aggregation reaction. To clarify how negative charge incorporation into tau directly affects aggregation behavior, the fibrillization of pseudophosphorylation mutant T212E prepared in a full-length four-repeat tau background was examined in vitro as a function of time and submicromolar tau concentrations using electron microscopy assay methods. Kinetic constants for nucleation and extension phases of aggregation were then estimated by direct measurement and mathematical simulation. Kinetic analysis revealed that pseudophosphorylation increased tau aggregation rate by increasing the rate of filament nucleation. In addition, it increased aggregation propensity by stabilizing mature filaments against disaggregation. The data suggest that incorporation of negative charge into the T212 site can directly promote tau filament formation at multiple steps in the aggregation pathway.
Collapse
Affiliation(s)
- Edward Chang
- Center of Molecular Neurobiology, Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | | | | | | |
Collapse
|
14
|
Yuzwa SA, Yadav AK, Skorobogatko Y, Clark T, Vosseller K, Vocadlo DJ. Mapping O-GlcNAc modification sites on tau and generation of a site-specific O-GlcNAc tau antibody. Amino Acids 2010; 40:857-68. [PMID: 20706749 DOI: 10.1007/s00726-010-0705-1] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 07/14/2010] [Indexed: 11/30/2022]
Abstract
The microtubule-associated protein tau is known to be post-translationally modified by the addition of N-acetyl-D: -glucosamine monosaccharides to certain serine and threonine residues. These O-GlcNAc modification sites on tau have been challenging to identify due to the inherent complexity of tau from mammalian brains and the fact that the O-GlcNAc modification typically has substoichiometric occupancy. Here, we describe a method for the production of recombinant O-GlcNAc modified tau and, using this tau, we have mapped sites of O-GlcNAc on tau at Thr-123 and Ser-400 using mass spectrometry. We have also detected the presence of a third O-GlcNAc site on either Ser-409, Ser-412, or Ser-413. Using this information we have raised a rabbit polyclonal IgG antibody (3925) that detects tau O-GlcNAc modified at Ser-400. Further, using this antibody we have detected the Ser-400 tau O-GlcNAc modification in rat brain, which confirms the validity of this in vitro mapping approach. The identification of these O-GlcNAc sites on tau and this antibody will enable both in vivo and in vitro experiments designed to understand the possible functional roles of O-GlcNAc on tau.
Collapse
Affiliation(s)
- Scott A Yuzwa
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada
| | | | | | | | | | | |
Collapse
|
15
|
Sun Q, Gamblin TC. Pseudohyperphosphorylation causing AD-like changes in tau has significant effects on its polymerization. Biochemistry 2009; 48:6002-11. [PMID: 19459590 DOI: 10.1021/bi900602h] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The microtubule-associated protein tau, in a hyperphosphorylated form, aggregates into insoluble paired-helical filaments (PHFs) in Alzheimer's disease (AD) and other tauopathies. In AD, there is approximately 8 mol of phosphate per mole of tau distributed among approximately 30 PHF phosphorylation sites as compared to 2-3 mol of phosphate per mole in normal brain. In AD, kinases such as glycogen synthase kinase-3beta (GSK-3beta) are believed to be involved in the generation of hyperphosphorylated tau. However, the functional consequences of hyperphosphorylation on the microtubule binding and polymerization of tau are not well understood. To address this question, we have generated pseudohyperphosphorylation mutants consisting of six and seven sites in the proline-rich region and carboxy terminus of tau by amino acid substitution. In addition, several single, double, and triple pseudophosphorylation mutants were also generated. Pseudophosphorylation of tau decreases its affinity for microtubules, and pseudohyperphosphorylated forms of tau do not have significantly decreased levels of microtubule binding as compared to single and double sites. Three pseudohyperphosphorylated forms of tau with altered sodium dodecyl sulfate-polyacrylamide gel electrophoresis migration have a greater effect on its inducer-mediated polymerization, slowing the rate of nucleation and elongation. On the basis of the observations that pseudohyperphosphorylated tau has decreased affinity for microtubules and reduced inducer-initiated rates of nucleation and polymerization, we propose that this combination could be the cause of the increased cytotoxicity of hyperphosphorylated tau in Alzheimer's disease and also explain the potentially beneficial role of tau polymerization and NFT formation.
Collapse
Affiliation(s)
- Qian Sun
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | | |
Collapse
|
16
|
Chang E, Kim S, Yin H, Nagaraja HN, Kuret J. Pathogenic missense MAPT mutations differentially modulate tau aggregation propensity at nucleation and extension steps. J Neurochem 2008; 107:1113-23. [PMID: 18803694 DOI: 10.1111/j.1471-4159.2008.05692.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mutations in the MAPT gene encoding tau protein lead to neurofibrillary lesion formation, neurodegeneration, and cognitive decline associated with frontotemporal lobar degeneration. While some pathogenic mutations affect MAPT introns, resulting in abnormal splicing patterns, the majority occur in the tau coding sequence leading to single amino acid changes in tau primary structure. Depending on their location within the polypeptide chain, tau missense mutations have been reported to augment aggregation propensity. To determine the mechanisms underlying mutation-associated changes in aggregation behavior, the fibrillization of recombinant pathogenic mutants R5L, G272V, P301L, V337M, and R406W prepared in a full-length four-repeat human tau background was examined in vitro as a function of time and submicromolar tau concentrations using electron microscopy assay methods. Kinetic constants for nucleation and extension phases of aggregation were then estimated by direct measurement and mathematical simulation. Results indicated that the mutants differ from each other and from wild-type tau in their aggregation propensity. G272V and P301L mutations increased the rates of both filament nucleation and extension reactions, whereas R5L and V337M increased only the nucleation phase. R406W did not differ from wild-type in any kinetic parameter. The results show that missense mutations can directly promote tau filament formation at different stages of the aggregation pathway.
Collapse
Affiliation(s)
- Edward Chang
- Department of Molecular and Cellular Biochemistry, Center for Molecular Neurobiology, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
| | | | | | | | | |
Collapse
|
17
|
Congdon EE, Kim S, Bonchak J, Songrug T, Matzavinos A, Kuret J. Nucleation-dependent tau filament formation: the importance of dimerization and an estimation of elementary rate constants. J Biol Chem 2008; 283:13806-16. [PMID: 18359772 DOI: 10.1074/jbc.m800247200] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Filamentous inclusions composed of the microtubule-associated protein tau are found in Alzheimer disease and other tauopathic neurodegenerative diseases, but the mechanisms underlying their formation from full-length protein monomer under physiological conditions are unclear. To address this issue, the fibrillization of recombinant full-length four-repeat human tau was examined in vitro as a function of time and submicromolar tau concentrations using electron microscopy assay methods and a small-molecule inducer of aggregation, thiazine red. Data were then fit to a simple homogeneous nucleation model with rate constant constraints established from filament dissociation rate, critical concentration, and mass-per-unit length measurements. The model was then tested by comparing the predicted time-dependent evolution of length distributions to experimental data. Results indicated that once assembly-competent conformations were attained, the rate-limiting step in the fibrillization pathway was tau dimer formation. Filament elongation then proceeded by addition of tau monomers to nascent filament ends. Filaments isolated at reaction plateau contained approximately 2 tau protomers/beta-strand spacing on the basis of mass-per-unit length measurements. The model suggests four key steps in the aggregation pathway that must be surmounted for tau filaments to form in disease.
Collapse
Affiliation(s)
- Erin E Congdon
- Center for Molecular Neurobiology, Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | | | | | | | | | | |
Collapse
|
18
|
Jia SH, Parodo J, Kapus A, Rotstein OD, Marshall JC. Dynamic regulation of neutrophil survival through tyrosine phosphorylation or dephosphorylation of caspase-8. J Biol Chem 2007; 283:5402-13. [PMID: 18086677 DOI: 10.1074/jbc.m706462200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Efficient expression of innate immunity is critically dependent upon the capacity of the neutrophil to be activated rapidly in the face of an acute threat and to involute once that threat has been eliminated. Here we report a novel mechanism regulating neutrophil survival dynamically through the tyrosine phosphorylation or dephosphorylation of caspase-8. Caspase-8 is tyrosine-phosphorylated in freshly isolated neutrophils but spontaneously dephosphorylates in culture, in association with the progression of constitutive apoptosis. Phosphorylation of caspase-8 on Tyr-310 facilitates its interaction with the Src-homology domain 2 containing tyrosine phosphatase-1 (SHP-1) and enables SHP-1 to dephosphorylate caspase-8, permitting apoptosis to proceed. The non-receptor tyrosine kinase, Lyn, can phosphorylate caspase-8 on Tyr-397 and Tyr-465, rendering it resistant to activational cleavage and inhibiting apoptosis. Exposure to lipopolysaccharide reduces SHP-1 activity and binding to caspase-8, caspase-8 activity, and rates of spontaneous apoptosis. SHP-1 activity is reduced and Lyn increased in neutrophils from patients with sepsis, in association with profoundly delayed apoptosis; inhibition of Lyn can partially reverse this delay. Thus the phosphorylation and dephosphorylation of caspase-8, mediated by Lyn and SHP-1, respectively, represents a novel, dynamic post-translational mechanism for the regulation of neutrophil apoptosis whose dysregulation contributes to persistent neutrophil survival in sepsis.
Collapse
Affiliation(s)
- Song Hui Jia
- Department of Surgery, University of Toronto, Toronto, Ontario, Canada
| | | | | | | | | |
Collapse
|
19
|
Ryoo SR, Jeong HK, Radnaabazar C, Yoo JJ, Cho HJ, Lee HW, Kim IS, Cheon YH, Ahn YS, Chung SH, Song WJ. DYRK1A-mediated hyperphosphorylation of Tau. A functional link between Down syndrome and Alzheimer disease. J Biol Chem 2007; 282:34850-7. [PMID: 17906291 DOI: 10.1074/jbc.m707358200] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most individuals with Down syndrome show early onset of Alzheimer disease (AD), resulting from the extra copy of chromosome 21. Located on this chromosome is a gene that encodes the dual specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A). One of the pathological hallmarks in AD is the presence of neurofibrillary tangles (NFTs), which are insoluble deposits that consist of abnormally hyperphosphorylated Tau. Previously it was reported that Tau at the Thr-212 residue was phosphorylated by Dyrk1A in vitro. To determine the physiological significance of this phosphorylation, an analysis was made of the amount of phospho-Thr-212-Tau (pT212) in the brains of transgenic mice that overexpress the human DYRK1A protein (DYRK1A TG mice) that we recently generated. A significant increase in the amount of pT212 was found in the brains of DYRK1A transgenic mice when compared with age-matched littermate controls. We further examined whether Dyrk1A phosphorylates other Tau residues that are implicated in NFTs. We found that Dyrk1A also phosphorylates Tau at Ser-202 and Ser-404 in vitro. Phosphorylation by Dyrk1A strongly inhibited the ability of Tau to promote microtubule assembly. Following this, using mammalian cells and DYRK1A TG mouse brains, it was demonstrated that the amounts of phospho-Ser-202-Tau and phospho-Ser-404-Tau are enhanced when DYRK1A amounts are high. These results provide the first in vivo evidence for a physiological role of DYRK1A in the hyperphosphorylation of Tau and suggest that the extra copy of the DYRK1A gene contributes to the early onset of AD.
Collapse
Affiliation(s)
- Soo-Ryoon Ryoo
- Graduate Program in Neuroscience, Institute for Brain Science and Technology, Inje University, Busan 614-735, South Korea
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Chun W, Waldo GS, Johnson GVW. Split GFP complementation assay: a novel approach to quantitatively measure aggregation of tau in situ: effects of GSK3beta activation and caspase 3 cleavage. J Neurochem 2007; 103:2529-39. [PMID: 17908237 DOI: 10.1111/j.1471-4159.2007.04941.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
To quantitatively measure tau aggregation in situ, we established a cell model system using a split green fluorescence protein (GFP) complementation assay. In this assay the more aggregated the protein of interest the lower the GFP fluorescence. Tau microtubule-binding domain constructs, whose aggregation characteristics have been described previously (Khlistunova et al. 2006), were used to validate the assay. The aggregation-prone construct exhibited the lowest GFP intensity whereas the aggregation-resistant construct showed the highest GFP intensity. To examine the role of glycogen synthase kinase 3beta (GSK3beta) activity and caspase 3 cleavage on tau aggregation, GFP complementation of full length (T4), caspase-cleaved (T4C3), and pseudophosphorylated at S396/S404 (T4-2EC) tau was examined in the presence of an active or a kinase-dead GSK3beta. Extensive phosphorylation of T4 by GSK3beta resulted in increased GFP intensity. T4C3 showed neither efficient phosphorylation nor a significant GFP intensity change by GSK3beta. The GFP intensity of T4-2EC was significantly reduced by GSK3beta accompanying its presence in the sarkosyl-insoluble fraction, thus demonstrating that T4-2EC was partitioning into aggregates. This indicates that if the majority of tau is phosphorylated at S396/S404, in combination with increased GSK3beta activity, tau aggregation is favored. These data demonstrate that split GFP complementation may be a valuable approach to determine the aggregation process in living cells.
Collapse
Affiliation(s)
- Wanjoo Chun
- Department of Psychiatry, University of Alabama at Birmingham School of Medicine, Alabama, USA
| | | | | |
Collapse
|
21
|
Chang E, Kuret J. Detection and quantification of tau aggregation using a membrane filter assay. Anal Biochem 2007; 373:330-6. [PMID: 17949677 DOI: 10.1016/j.ab.2007.09.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Revised: 09/12/2007] [Accepted: 09/14/2007] [Indexed: 11/19/2022]
Abstract
Aggregation of the microtubule-associated protein tau contributes to the formation of neurofibrillary lesions in Alzheimer's disease and is a useful marker of disease progression. Although filter trap assays have been employed to assess the extent of tau aggregation in cells and tissues as well as in vitro, their performance relative to other assay modalities has not been reported. To clarify this issue, the ability of the filter trap approach to quantify aggregation of purified recombinant full-length tau protein in vitro was examined as a function of membrane chemistry in a 96-well format. Results showed that nitrocellulose yielded the greatest assay sensitivity relative to polyvinylidene fluoride or cellulose acetate at equal membrane porosity. However, all combinations of filter chemistries, porosities, and monoclonal detection antibodies yielded nonlinear correlations between signal intensity and analyte concentration. When corrected for nonlinearity, the filter trap assay determined a value for the critical monomer concentration for tau aggregation that was statistically identical to determinations made by electron microscopy assay. The data suggest conditions under which filter trap assays can be used to estimate tau aggregation kinetics.
Collapse
Affiliation(s)
- Edward Chang
- Integrated Biomedical Sciences Graduate Program, Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | | |
Collapse
|
22
|
Chun W, Johnson GVW. Activation of Glycogen Synthase Kinase 3β Promotes the Intermolecular Association of Tau. J Biol Chem 2007; 282:23410-7. [PMID: 17565981 DOI: 10.1074/jbc.m703706200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Tau is hyperphosphorylated and undergoes proteolysis in Alzheimer disease brain. Caspase-cleaved tau efficiently forms fibrillary structures in vitro and in situ. Glycogen synthase kinase 3beta (GSK3beta) phosphorylates tau and induces the aggregation of caspase-cleaved tau in situ. Given the hypothesis that increased association of tau precedes the formation of fibrillar structures, we generated a cell model to quantitate the extent of tau association in situ using fluorescence resonance energy transfer (FRET) microscopy. The cyan and yellow fluorescent proteins were attached to full-length (T4) and caspase-cleaved (T4C3) tau at either the N or C termini, and a pair of cyan and yellow fluorescent protein-tagged tau were co-transfected into human embryonic kidney cells. The FRET efficiency was examined in the presence of a constitutively active or a kinase-dead GSK3beta. Active GSK3beta significantly increased FRET efficiency with both T4 and T4C3, indicating that GSK3beta activation resulted in an increase in the self-association of both T4 and T4C3, but interestingly only T4 is efficiently phosphorylated by GSK3beta. There was no significant difference in FRET efficiency between T4 and T4C3, although only T4C3 in the presence of active GSK3beta leads to the formation of Sarkosyl-insoluble inclusions. These FRET studies demonstrate that GSK3beta facilitates the association of T4 and T4C3, and the presence of caspase-cleaved tau is necessary for the evolution of tau oligomers into Sarkosyl-insoluble inclusions even though it is not extensively phosphorylated. These data imply that increased association of tau should not be regarded as a direct indicator of the formation of insoluble tau aggregates.
Collapse
Affiliation(s)
- Wanjoo Chun
- Department of Psychiatry, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama 35294, USA
| | | |
Collapse
|
23
|
Congdon EE, Necula M, Blackstone RD, Kuret J. Potency of a tau fibrillization inhibitor is influenced by its aggregation state. Arch Biochem Biophys 2007; 465:127-35. [PMID: 17559794 PMCID: PMC2048980 DOI: 10.1016/j.abb.2007.05.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2007] [Revised: 05/07/2007] [Accepted: 05/08/2007] [Indexed: 11/17/2022]
Abstract
Tau fibrillization is a potential therapeutic target for Alzheimer's and other neurodegenerative diseases. Several small-molecule inhibitors of tau aggregation have been developed for this purpose. One of them, 3,3'-bis(beta-hydroxyethyl)-9-ethyl-5,5'-dimethoxythiacarbocyanine iodide (N744), is a cationic thiacarbocyanine dye that inhibits recombinant tau filament formation when present at submicromolar concentrations. To prepare dosing regimens for testing N744 activity in biological models, its full concentration-effect relationship in the range 0.01-60muM was examined in vitro by electron microscopy and laser light scattering methods. Results revealed that N744 concentration dependence was biphasic, with fibrillization inhibitory activity appearing at submicromolar concentration, but with relief of inhibition and increases in fibrillization apparent above 10muM. Therefore, fibrillization was inhibited 50% only over a narrow concentration range, which was further reduced by filament stabilizing modifications such as tau pseudophosphorylation. N744 inhibitory activity also was paralleled by changes in its aggregation state, with dimer predominating at inhibitory concentrations and large dye aggregates appearing at high concentrations. Ligand dimerization was promoted by the presence of tau protein, which lowered the equilibrium dissociation constant for dimerization more than an order of magnitude relative to controls. The results suggest that ligand aggregation may play an important role in both inhibitory and disinhibitory phases of the concentration-effect curve, and may lead to complex dose-response relationships in model systems.
Collapse
Affiliation(s)
- Erin E. Congdon
- Neuroscience Graduate Studies Program, The Ohio State University, Columbus, OH 43210
| | - Mihaela Necula
- Biophysics Program, The Ohio State University, Columbus, OH 43210
| | - Robert D. Blackstone
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
| | - Jeff Kuret
- Center for Molecular Neurobiology, The Ohio State University, Columbus, OH 43210
- *Corresponding Author: Jeff Kuret, Ph.D., Center for Molecular Neurobiology 1060 Carmack Rd. Columbus, OH 43210, TEL: (614) 688-5899, FAX: (614) 292-5379,
| |
Collapse
|
24
|
Abstract
Alzheimer's disease is characterized by two protein precipitates, extracellular amyloid plaques and intracellular neurofibrillary tangles (NFTs). The primary constituent of NFTs is a hyperphosphorylated form of the microtubule-binding protein tau. Hyperphosphorylation of tau on over 30 residues, primarily within proline-rich sequences, is associated with conformational changes whose nature is poorly defined. Peptides derived from the proline-rich region of tau (residues 174-242) were synthesized, and the conformations were analyzed for the nonphosphorylated and phosphorylated peptides. CD and NMR data indicate that phosphorylation of serine and threonine residues in proline-rich sequences induces a conformational change to a type II polyproline helix. The largest phosphorylation-dependent conformational changes observed by CD were for tau peptides incorporating residues 174-183 or residues 229-238. Phosphoserine and phosphothreonine residues exhibited ordered values of (3)J(alphaN) (3.1-6.2 Hz; mean = 4.7 Hz) compared to nonphosphorylated serine and threonine. Phosphorylation of a tau peptide consisting of tau residues 196-209 resulted in the disruption of a nascent alpha-helix. These results suggest that global reorganization of tau may occur upon hyperphosphorylation of proline-rich sequences in tau.
Collapse
Affiliation(s)
- Agata A Bielska
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
| | | |
Collapse
|
25
|
Guillozet-Bongaarts AL, Cahill ME, Cryns VL, Reynolds MR, Berry RW, Binder LI. Pseudophosphorylation of tau at serine 422 inhibits caspase cleavage: in vitro evidence and implications for tangle formation in vivo. J Neurochem 2006; 97:1005-14. [PMID: 16606369 DOI: 10.1111/j.1471-4159.2006.03784.x] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The tangles of Alzheimer's disease (AD) are comprised of the tau protein displaying numerous alterations, including phosphorylation at serine 422 (S422) and truncation at aspartic acid 421 (D421). Truncation at the latter site appears to result from activation of caspases, a class of proteases that cleave specifically at aspartic acid residues. It has been proposed that phosphorylation at or near caspase cleavage sites could regulate the ability of the protease to cleave at those sites. Here, we use tau pseudophosphorylated at S422 (S422E) to examine the effects of tau phosphorylation on its cleavage by caspase 3. We find that S422E tau is more resistant to proteolysis by caspase 3 than non-pseudophosphorylated tau. Additionally, we use antibodies directed against the phosphorylation site and against the truncation epitope to assess the presence of these epitopes in neurofibrillary tangles in the aged human brain. We show that phosphorylation precedes truncation during tangle maturation. Moreover, the distribution of the two epitopes suggests that a significant length of time (perhaps as much as two decades) elapses between S422 phosphorylation and cleavage at D421. We further conclude that tau phosphorylation at S422 may be a protective mechanism that inhibits cleavage in vivo.
Collapse
Affiliation(s)
- Angela L Guillozet-Bongaarts
- Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
| | | | | | | | | | | |
Collapse
|
26
|
Kraemer BC, Burgess JK, Chen JH, Thomas JH, Schellenberg GD. Molecular pathways that influence human tau-induced pathology in Caenorhabditis elegans. Hum Mol Genet 2006; 15:1483-96. [PMID: 16600994 DOI: 10.1093/hmg/ddl067] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mutations in the gene encoding tau cause frontotemporal dementia with parkinsonism--chromosome 17 type (FTDP-17). In FTDP-17, Alzheimer's disease, and other tauopathies, aggregated hyper-phosphorylated tau forms the neurofibrillary tangles characteristic of these disorders. We previously reported a Caenorhabditis elegans model for tauopathies using human normal and FTDP-17 mutant tau as transgenes. Neuronal transgene expression caused insoluble phosphorylated tau accumulation, neurodegeneration and uncoordinated (Unc) movement. Here we describe a genome-wide RNA-mediated interference (RNAi) screen for genes that modify the tau-induced Unc phenotype. We tested RNAi sequences for 16,757 genes and found 75 that enhanced the transgene-induced Unc phenotype. Forty-six of these genes have sequence similarity to known human genes and fall into a number of broad classes including kinases, chaperones, proteases and phosphatases. The remaining 29 modifiers have sequence similarity only with other nematode genes. To determine if the enhancers are specific for the tau-induced Unc behavior, we exposed several non-tau Unc mutants to tau RNAi enhancer clones. Fifteen enhancers modified phenotypes in multiple Unc mutants, whereas 60 modified only the Unc phenotype in the tau transgenic lines. We also introduced the tau transgene into the background of genetic loss-of-function mutations for a subset of the enhancer genes. Tau transgenic animals homozygous for loss of these enhancer genes exhibited increased impaired motility relative to the tau transgene line alone. This work uncovers novel candidate genes that prevent tau toxicity, as well as genes previously implicated in tau-mediated neurodegeneration.
Collapse
Affiliation(s)
- Brian C Kraemer
- Geriatrics Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108-1597, USA
| | | | | | | | | |
Collapse
|
27
|
Sarthy J, Gamblin TC. A light scattering assay for arachidonic acid-induced tau fibrillization without interfering micellization. Anal Biochem 2006; 353:150-2. [PMID: 16620751 DOI: 10.1016/j.ab.2006.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Revised: 03/02/2006] [Accepted: 03/07/2006] [Indexed: 11/16/2022]
Affiliation(s)
- Jay Sarthy
- Department of Molecular Biosciences, University of Kansas, Lawrence, 66045, USA
| | | |
Collapse
|
28
|
Yin H, Kuret J. C-terminal truncation modulates both nucleation and extension phases of τ fibrillization. FEBS Lett 2005; 580:211-5. [PMID: 16364303 DOI: 10.1016/j.febslet.2005.11.077] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 11/30/2005] [Indexed: 11/16/2022]
Abstract
Proteolytic post-translational modification has been proposed as an early stage event in the aggregation of tau protein and formation of neurofibrillary lesions in Alzheimer's disease. Caspases and other proteases cleave tau in vivo at discrete locations including Asp421 and Glu391. Both cleavage products are prone to aggregation relative to wild-type, full-length tau protein. To determine the mechanism underlying this effect, the fibrillization of tau truncated after Asp421 and Glu391 residues was characterized in a full-length four-repeat tau background using quantitative electron microscopy methods under homogeneous nucleation conditions. Both C-terminal truncations decreased critical concentration relative to full-length tau, resulting in more filament mass at reaction plateau. Moreover, truncation directly augmented the efficiency of the nucleation reaction. The results suggest the mechanism through which C-terminal proteolysis can modulate tau filament accumulation depending on whether it precedes or follows nucleation.
Collapse
Affiliation(s)
- Haishan Yin
- Ohio State Biochemistry Program, The Ohio State University College of Medicine and Public Health, Columbus, OH 43210, USA
| | | |
Collapse
|
29
|
Necula M, Chirita CN, Kuret J. Cyanine dye N744 inhibits tau fibrillization by blocking filament extension: implications for the treatment of tauopathic neurodegenerative diseases. Biochemistry 2005; 44:10227-37. [PMID: 16042400 DOI: 10.1021/bi050387o] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Tau fibrillization is a potential therapeutic target for Alzheimer's and other neurodegenerative diseases. Small molecules capable of both inhibiting aggregation and promoting filament disaggregation have been discovered, but knowledge of their mechanism of action and potential for testing in biological models is fragmentary. To clarify these issues, the interaction between a small-molecule inhibitor of tau fibrillization, 3,3'-bis(beta-hydroxyethyl)-9-ethyl-5,5'-dimethoxythiacarbocyanine iodide (N744), and full-length four-repeat tau protein was characterized in vitro using transmission electron microscopy and fluorescence spectroscopy. Analysis of reaction time courses performed in the presence of anionic fibrillization inducers revealed that increasing concentrations of N744 decreased the total filament length without modulating lag time, indicating that filament extension but not nucleation was affected by inhibitor under the conditions that were investigated. Critical concentration measurements confirmed that N744 shifted equilibria at filament ends away from the fibrillized state, resulting in endwise filament disaggregation when it was added to synthetic filaments. Both increasing bulk tau concentrations and filament stabilizing modifications such as pseudophosphorylation and glycation antagonized N744 activity. The results illustrate the importance of mechanism for the design and interpretation of pharmacological studies in biological models of tau aggregation.
Collapse
Affiliation(s)
- Mihaela Necula
- Biophysics Program, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA
| | | | | |
Collapse
|
30
|
Kuret J, Congdon EE, Li G, Yin H, Yu X, Zhong Q. Evaluating triggers and enhancers of tau fibrillization. Microsc Res Tech 2005; 67:141-55. [PMID: 16103995 DOI: 10.1002/jemt.20187] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alzheimer's disease is characterized in part by the aggregation of tau protein into filamentous inclusions. Because tau filaments form in brain regions associated with memory retention, and because their appearance correlates well with the degree of dementia, they have emerged as robust markers of disease progression. Yet the discovery that mutations in tau protein can lead directly to filament and tangle formation in humans, and that filament formation is linked to neurodegeneration in model biological systems, suggests that tau aggregation may also contribute directly to degeneration in affected neurons. In this context, the mechanism of tau filament formation and its modulation by mutation and posttranslational modification is of fundamental importance. Here, recent progress on the molecular mechanisms underlying tau aggregation deduced from in vivo and in vitro experimentation is reviewed and a model rationalizing the effect of posttranslational and other structural modifications on assembly kinetics and thermodynamics is presented. We hypothesize that tau aggregation can be described as a heterogeneous nucleation reaction, where exogenous effectors, tau gene mutations, or other modifications that stabilize assembly-competent conformations of tau act to trigger the fibrillization reaction. In contrast, those that modulate postnuclear equilibria can enhance fibrillization by increasing the free energy difference between polymers and unincorporated monomers, resulting in stabilization of filaments at low bulk protein concentrations.
Collapse
Affiliation(s)
- Jeff Kuret
- Department of Molecular and Cellular Biochemistry and Center for Molecular Neurobiology, The Ohio State University College of Medicine and Public Health, Columbus, Ohio 43210, USA.
| | | | | | | | | | | |
Collapse
|