In Vitro Polymerization of Embryonic MAP-2c and Fragments of the MAP-2 Microtubule Binding Region into Structures Resembling Paired Helical Filaments

DeTure, Michael; Zhang, Edith Yi; Bubb, Michael R.; Purich, Daniel L.

doi:10.1074/jbc.271.51.32702

Cited by 16 publications

(17 citation statements)

References 28 publications

(32 reference statements)

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“…1, inset, for typical morphologies), whereas the MTBR of MAP2 only forms straight filaments. Because bacterially expressed MAP2 MTBR and Tau MTBR have the same filament polymerization habits as the proteins isolated directly from brain tissue (13)(14)(15)(16)19), post-translational modification is not required for these differences in filament morphology. We therefore considered the possibility that one or more amino acid residues in their MTBRs is(are) somehow playing a mor- phology-determining role.…”

Section: Resultsmentioning

confidence: 99%

“…Upon overnight dialysis in the absence of a thiol reducing agent, MTBR-mod A (HGKYP) formed the disulfide cross-linked dimer (lane 1 of Fig. 3A) which is known to hasten filament self-assembly (13)(14)(15)22). As shown in lane 2, treatment with 4 mM dithiothreitol converts the cross-linked dimer into monomer.…”

Section: Resultsmentioning

confidence: 99%

“…Schweers et al (13) advanced our understanding of Tau polymerization by describing how disulfide-linked dimers more readily assemble into PHF-like structures. Our laboratory made the unprecedented finding that the MTBR of MAP2 as well as full-length MAP2c form straight filaments in vitro (14,15), indicating that there is no clear explanation for why AD neurofibrillary pathology strictly involves Tau. Despite numerous attempts to modify solution conditions to favor the assembly of paired-helical filaments, we consistently observed that wild-type MAP2 MTBR could not form PHF structures.…”

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In Vitro Assembly of Alzheimer-like Filaments

DeTure

Noto

Purich

2002

Journal of Biological Chemistry

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Although the microtubule-binding regions (MTBRs) of both Tau and MAP2 can undergo self-assembly into straight filaments (SFs) in vitro, only the Tau MTBR forms paired helical filaments (PHFs). Moreover, Tau appears to be the exclusive building block of the neuropathic filaments observed in Alzheimer's disease and certain frontotemporal dementias (FTDs). Despite significant conservation in the MTBR sequences, there are two persistently different stretches of amino acids (designated here as Module-A and Module-B) between Tau and MAP2 from a number of organisms. To evaluate the role of charged residues in these modules as potential morphology-specifying elements, we used site-directed mutagenesis to replace selected residues within the MAP2 MTBR by residues at corresponding positions in Tau. We then employed electron microscopy to determine the frequency of occurrence of SF and PHF morphology in filaments assembled from these mutant microtubule-binding regions. Our experimental results indicate that a very small number of residues are especially significant determinants of filament morphology; this inference is also supported by the observation that site-directed substitutions of individual Tau residues into MAP2 Module-B likewise result in the formation of PHF-like structures. Because the Module-B in Tau contains two naturally occurring FTD mutations, residues in this region may play a critical role in neuropathic filament assembly.The mechanism of nerve cell degeneration/death in Alzheimer's disease (AD) 1 and related Chromosome-17 tauopathies remains uncertain. Dysfunctional ␤-amyloid protein processing appears to be significant in AD progression (1), culminating in cellular oxidative stress as well as formation of plaques comprised of amyloid ␤-protein. AD brain also exhibits extensive pathology, chiefly in the form of neurofibrillary tangles (NFTs), the abnormal cytoplasmic fibrous aggregates associated with dead or dying neurons in the hippocampus and amygdala. Kidd (2) and Terry (3) found that NFTs consist mainly of paired helical filaments (PHFs) and straight filaments (SFs). Wischik et al. (4) made the seminal finding that the brain microtubuleassociated protein Tau is the basic building block of AD filaments. Tau and other structurally related MAPs use their highly conserved microtubule-binding regions (MTBRs) to interact with assembled microtubules (5-7), and the MTBR of Tau comprises the core structure of PHF. Other NFT-producing neurodegenerative diseases result from point mutations in or near the MTBR of Tau (8 -10), underscoring the concept that NFT formation stems from modifications within the MTBR of Tau.Crowther et al. (11) first described the in vitro assembly of Alzheimer-like filaments from a 99-residue Tau fragment containing the microtubule binding repeats, and Wilson and Binder (12) demonstrated that full-length Tau also forms filaments. Schweers et al. (13) advanced our understanding of Tau polymerization by describing how disulfide-linked dimers more readily assemble into PHF-like struct...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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In Vitro Assembly of Alzheimer-like Filaments

DeTure

Noto

Purich

2002

Journal of Biological Chemistry

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“…Despite the still unclear role of MAP1B and MAP2 in AD-associated neurodegeneration, several studies have highlighted the possible involvement of aberrant phosphorylation and proteolysis in several fragments (35,54,55), leading to MAP incorporation into PHFs as effectors of neurodegeneration in AD. Moreover, it has been demonstrated that small MAP2a and MAP2b fragments and MAP2c (via their microtubule-binding region) readily polymerize into structures resembling PHFs (37).…”

Section: Discussionmentioning

confidence: 99%

“…A region-specific increase in calpain activity has been demonstrated in the early stages of AD development, even before synaptic loss, neuronal degeneration, and tau hyperphosphorylation and aggregation (33). Moreover, in AD brain, the active form of calpain co-localizes with NFTs, senile plaques, and neuropil threads (34), just like MAP1B and MAP2 (35,36), which supports the capacity of MAP2 to form structures resembling PHFs via its microtubule-binding region (37). Moreover, MAP1 and MAP2 or their proteolytic products have been suggested to act as effectors of cell death in AD (1,38).…”

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confidence: 93%

Microtubule-associated Protein MAP1A, MAP1B, and MAP2 Proteolysis during Soluble Amyloid β-Peptide-induced Neuronal Apoptosis

Fifre¹,

Sponne²,

Koziel³

et al. 2006

Journal of Biological Chemistry

108

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A growing body of evidence supports the notion that soluble oligomeric forms of the amyloid ␤-peptide (A␤) may be the proximate effectors of neuronal injuries and death in the early stages of Alzheimer disease. However, the molecular mechanisms associated with neuronal apoptosis induced by soluble A␤ remain to be elucidated. We recently demonstrated the involvement of an early reactive oxygen species-dependent perturbation of the microtubule network (Sponne, I., Fifre, A., Drouet, B., Klein, C., Koziel, V., Pincon-Raymond, M., Olivier, J.-L., Chambaz, J., and Pillot, T. Microtubules are polymers of ␣-and ␤-tubulin dimers that mediate many functions in neurons, including organelle transport and cell shape establishment and maintenance as well as axonal elongation and growth cone steering in neurons. The polymerization, stabilization, and dynamic properties of microtubules are influenced by interactions with microtubule-associated proteins (MAPs).3 Members of this protein family are classified by size: high molecular mass proteins (MAP1A, MAP1B, MAP2a, and MAP2b) and intermediate molecular mass proteins (MAP2c, MAP2d, and tau) (1-3). Numerous studies have shown that neuronal apoptotic cell death involves alterations of the microtubule network consequent to calpain and effector caspase activation (4, 5). These calcium-dependent proteases are responsible for the degradation and turnover of a broad repertoire of MAP substrates, some of which they share, such as ␣II-spectrin and tau, and some of which are specific, as is the case of calpain-degraded MAP1B and MAP2.Intraneuronal neurofibrillary tangles (NFTs) are one of the histopathological hallmarks in brains of patients diagnosed with Alzheimer disease (AD), a progressive dementia that manifests primarily as a profound inability to form new memories. These NFTs are composed of hyperphosphorylated tau organized into paired helical filaments (PHFs) (6). In addition, AD is also associated with the presence of extracellular senile plaques (7) formed as a consequence of the gradual accumulation and aggregation of the amyloid ␤-peptide (A␤) into fibrils (8). Despite evidence that A␤ represents a key factor in AD (9), the nature of the toxic form of A␤ involved early in AD pathology remains to be determined. The issue of which pool (soluble or aggregated) of A␤ in brain is more deleterious in the early stages of AD is still controversial (10). However, clinicopathological hallmarks of AD correlate far better with the soluble pool of A␤ (11,12). Moreover, several studies in transgenic mice have indicated that specific cognitive deficits, neurodegeneration, and synaptic loss might occur before any histologically detectable formation of senile plaques (13,14). So, in reports from our group (15-18) and others (19,20), attention has been paid to the soluble oligomeric forms of A␤ as the principal mediators of neurodegeneration in the early stages of AD development (10, 19 -23).Increasing evidence suggests that the selective neuronal cell death in AD involves activation of caspa...

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Structural insights into Alzheimer filament assembly pathways based on site‐directed mutagenesis and S‐glutathionylation of three‐repeat neuronal Tau protein

DiNoto

DeTure

Purich

2005

Microscopy Res & Technique

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Although Tau and MAP2 readily assemble into straight filaments (SFs), Tau's unique ability to form paired-helical filaments (PHFs) may offer clues as to why Tau's microtubule-binding region (MTBR) is the exclusive building block of the neurofibrillary tangles that accumulate during Alzheimer's disease. To learn more about the factors permitting Tau to form both SFs and PHFs, we investigated the microtubule binding, thiol oxidation, and polymerization reactions of the monomer and dimer forms of Tau and MAP2 MTBRs. This review focuses on electron microscopic evidence (1) that facilitated the identification of amino acid residues within 3-repeat Tau that promote PHF formation; and (2) provided experimental evidence for the polymerization of S-glutathionylated three-repeat Tau, a reaction that unambiguously demonstrates that disulfide-linked Tau-S-S-Tau dimer formation is not a compulsory step in filament assembly. We also consider these findings within the context of current views on the genetic and biochemical basis of Tau fibrillogenesis.

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In Vitro Polymerization of Embryonic MAP-2c and Fragments of the MAP-2 Microtubule Binding Region into Structures Resembling Paired Helical Filaments

Cited by 16 publications

References 28 publications

In Vitro Assembly of Alzheimer-like Filaments

In Vitro Assembly of Alzheimer-like Filaments

Microtubule-associated Protein MAP1A, MAP1B, and MAP2 Proteolysis during Soluble Amyloid β-Peptide-induced Neuronal Apoptosis

Structural insights into Alzheimer filament assembly pathways based on site‐directed mutagenesis and S‐glutathionylation of three‐repeat neuronal Tau protein

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