High intergrain critical current density in fine-grain (Ba0.6K0.4)Fe2As2 wires and bulks

The K- and Co-doped BaFe(2)As(2) (Ba-122) superconducting compounds are potentially useful for applications because they have upper critical fields (H(c2)) of well over 50 T, H(c2) anisotropy γ < 2and thin-film critical current densities J(c) exceeding 1 MA cm(-2) (refs 1-4) at 4.2 K. However, thin-film bicrystals of Co-doped Ba-122 clearly exhibit weak link behaviour for [001] tilt misorientations of more than about 5°, suggesting that textured substrates would be needed for applications, as in the cuprates. Here we present a contrary and very much more positive result in which untextured polycrystalline (Ba(0.6)K(0.4))Fe(2)As(2) bulks and round wires with high grain boundary density have transport critical current densities well over 0.1 MA cm(-2) (self-field, 4.2 K), more than 10 times higher than that of any other round untextured ferropnictide wire and 4-5 times higher than the best textured flat wire. The enhanced grain connectivity is ascribed to their much improved phase purity and to the enhanced vortex stiffness of this low-anisotropy compound (γ~1-2) when compared with YBa(2)Cu(3)O(7-x) (γ~5).

Neuronal β-amyloid generation is independent of lipid raft association of β-secretase BACE1: analysis with a palmitoylation-deficient mutant

β-Secretase, BACE1 is a neuron-specific membrane-associated protease that cleaves amyloid precursor protein (APP) to generate β-amyloid protein (Aβ). BACE1 is partially localized in lipid rafts. We investigated whether lipid raft localization of BACE1 affects Aβ production in neurons using a palmitoylation-deficient mutant and further analyzed the relationship between palmitoylation of BACE1 and its shedding and dimerization. We initially confirmed that BACE1 is mainly palmitoylated at four C-terminal cysteine residues in stably transfected neuroblastoma cells. We found that raft localization of mutant BACE1 lacking the palmitoylation modification was markedly reduced in comparison to wild-type BACE1 in neuroblastoma cells as well as rat primary cortical neurons expressing BACE1 via recombinant adenoviruses. In primary neurons, expression of wild-type and mutant BACE1 enhanced production of Aβ from endogenous or overexpressed APP to similar extents with the β-C-terminal fragment (β-CTF) of APP mainly distributed in nonraft fractions. Similarly, β-CTF was recovered mainly in nonraft fractions of neurons expressing Swedish mutant APP only. These results show that raft association of BACE1 does not influence β-cleavage of APP and Aβ production in neurons, and support the view that BACE1 cleaves APP mainly in nonraft domains. Thus, we propose a model of neuronal Aβ generation involving mobilization of β-CTF from nonraft to raft domains. Additionally, we obtained data indicating that palmitoylation plays a role in BACE1 shedding but not dimerization.

Postmortem findings in a patient with cerebral amyloid angiopathy actively treated with corticosteroid

We examined histopathological changes in cerebrovascular amyloid deposition in a patient with cerebral amyloid angiopathy receiving corticosteroid therapy. A 69-year-old female developed subacute onset cognitive decline, and magnetic resonance image (MRI) showed subarachnoid hemorrhage with leptomeningeal enhancement. She entered in an apathetic state due to communicating hydrocephalus and a ventricle-peritoneal (V-P) shunt operation was performed. Brain biopsy disclosed multiple cortical microhemorrhages and severe Congophilic angiopathy with positive Aβ-immunoreactivity in most vessels. Inflammatory mononuclear cells surrounded a few severe amyloid-laden leptomeningeal vessels. She received high-dose corticosteroid, which was slowly tapered. She gradually recovered but finally died 1.5 years later with no recurrence of CAA-related hemorrhages. Postmortem examination of the brain showed multiple old microhemorrhages in the cortex and extensive degeneration of cerebral white matter. The cortical and leptomeningeal vascular walls showed a few Congophilic amyloid deposits, but small deposits with Aβ-immunoreactivity were frequently seen. There was no infiltration of inflammatory cells in either leptomeninges or vascular walls. Electron microscopy revealed sparse aggregation of amyloid fibrils in significant numbers of vascular walls. Biochemical analysis disclosed that Aβ1-40-immunoreactive amyloid protein fractions obtained from the patient's leptomeninges were very small in amount. Comparing the previous biopsy findings with those at autopsy, the total disappearance of the inflammatory cell infiltration and diminishing of the cerebrovascular amyloid deposits were noted.

Epitope mapping of antibodies against TDP-43 and detection of protease-resistant fragments of pathological TDP-43 in amyotrophic lateral sclerosis and frontotemporal lobar degeneration

TAR DNA-binding protein of 43 kDa (TDP-43) is the major component of the intracellular inclusions in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Here, we show that both monoclonal (60019-2-Ig) and polyclonal (10782-2-AP) anti-TDP-43 antibodies recognize amino acids 203-209 of human TDP-43. The monoclonal antibody labeled human TDP-43 by recognizing Glu204, Asp205 and Arg208, but failed to react with mouse TDP-43. The antibodies stained the abnormally phosphorylated C-terminal fragments of 24-26 kDa in addition to normal TDP-43 in ALS and FTLD brains. Immunoblot analysis after protease treatment demonstrated that the epitope of the antibodies (residues 203-209) constitutes part of the protease-resistant domain of TDP-43 aggregates which determine a common characteristic of the pathological TDP-43 in both ALS and FTLD-TDP. The antibodies and methods used in this study will be useful for the characterization of abnormal TDP-43 in human materials, as well as in vitro and animal models for TDP-43 proteinopathies.

[Molecular dissection of TDP-43 in ALS and FTLD]

Proteomic and immunochemical analyses have shown that hyperphosphorylated TDP-43 is a major component of ubiquitin-positive inclusions from brain of frontotemporal lobar degeneration (FTLD) patients. In 2008, TDP-43 gene mutations were discovered in familial and sporadic amyotrophic lateral sclerosis (ALS), indicating that TDP-43 protein abnormality is associated with neurodegeneration. We raised antibodies against 36 synthetic phosphopeptides and demonstrated that abnormal phosphorylation takes place in the C-terminal region of TDP-43. One antibody, pS409/410, stained the inclusions in both FTLD and ALS brains, with no nuclear staining. Immunoblotting revealed the presence of hyperphosphorylated 45 kDa band, smearing substances and 18-26 kDa fragments in deposits, and the band patterns were different between FTLD and ALS. Overexpression of TDP-43 C-terminal fragments as GFP-fusions resulted in formation of inclusions positive for antibodies to phosphorylated TDP-43 and ubiquitin. We further investigated the protease-resistant TDP-43 and found that it is also different between ALS and FTLD, supporting the idea that the different band patterns reflect different conformations of abnormal TDP-43. Interestingly, the C-terminal band pattern is indistinguishable among brain regions and spinal cord in each individual patient. These results suggest that abnormal TDP-43 produced in a cell may be transferred to different regions and propagated during disease progression.

Molecular dissection of TDP-43 proteinopathies

TDP-43 has been identified as a major component of ubiquitin-positive tau-negative cytoplasmic inclusions in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and in amyotrophic lateral sclerosis (ALS). We raised antibodies to phosphopeptides representing 36 out of 64 candidate phosphorylation sites of human TDP-43 and showed that the antibodies to pS379, pS403/404, pS409, pS410 and pS409/410 labeled the inclusions, but not the nuclei. Immunoblot analyses demonstrated that the antibodies recognized TDP-43 at ~45 kDa, smearing substances and 18-26 kDa C-terminal fragments. Furthermore, the band patterns of the C-terminal fragments differed between neuropathological subtypes, but were indistinguishable between brain regions and spinal cord in each individual patient. Protease treatment of Sarkosyl-insoluble TDP-43 suggests that the different band patterns of the C-terminal fragments reflect different conformations of abnormal TDP-43 molecules between the diseases. These results suggest that molecular species of abnormal TDP-43 are different between the diseases and that they propagate from affected cells to other cells during disease progression and determine the clinicopathological phenotypes of the diseases.

Phosphorylated and cleaved TDP-43 in ALS, FTLD and other neurodegenerative disorders and in cellular models of TDP-43 proteinopathy

Transactivation response (TAR) DNA-binding protein of Mr 43 kDa (TDP-43) is a major component of the tau-negative and ubiquitin-positive inclusions that characterize amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration which is now referred to as FTLD-TDP. Concurrent TDP-43 pathology has been reported in a variety of other neurodegenerative disorders such as Alzheimer's disease, forming a group of TDP-43 proteinopathy. Accumulated TDP-43 is characterized by phosphorylation and fragmentation. There is a close relationship between the pathological subtypes of FTLD-TDP and the immunoblot pattern of the C-terminal fragments of phosphorylated TDP-43. These results suggest that proteolytic processing of accumulated TDP-43 may play an important role for the pathological process. In cultured cells, transfected C-terminal fragments of TDP-43 are more prone to form aggregates than full-length TDP-43. Transfecting the C-terminal fragment of TDP-43 harboring pathogenic mutations of TDP-43 gene identified in familial and sporadic ALS cases into cells enhanced the aggregate formation. Furthermore, we found that methylene blue and dimebon inhibit aggregation of TDP-43 in these cellular models. Understanding the mechanism of phosphorylation and truncation of TDP-43 and aggregate formation may be crucial for clarifying the pathogenesis of TDP-43 proteinopathy and for developing useful therapeutics.

[TDP-43 proteinopathies, toward understanding of the molecular pathogenesis]

The TDP-43 proteinopathies: Toward understanding of the molecular pathogenesis. TAR DNA binding protein of 43 kDa (TDP-43), a heterogeneous nuclear ribonucleoprotein was identified as a major component of ubiquitin-positive inclusions in FTLD and ALS, and the concept of TDP-43 proteinopathies was proposed. Immunoblot and immunohistochemical analyses using multiple anti-phosphorylated TDP-43 antibodies revealed that hyperphosphorylated 18-26 kDa C-terminal fragments in addition to the full-length TDP-43 are major constituents of inclusions in FTLD-U and ALS. Recent discovery of mutations in the TDP-43 gene in familial and sporadic ALS, indicating that abnormality of TDP-43 protein cause neurodegeneration. It also strongly suggests that aggregation of TDP-43 or the process is responsible for neurodegeneration in FTLD-U and ALS. To investigate the molecular mechanisms of aggregation of TDP-43, we have established two cellular models for intracellular aggregates of TDP-43 similar to those in brains of TDP-43 proteinopathies patients. The first consists of SH-SY5Y cells expressing mutant TDP-43 that lacks both the nuclear localization signal (NLS) and residues 187-192 (deltaNLS & 187-192). The second model consists of SH-SY5Y cells expressing an aggregation-prone TDP-43 C-terminal fragment as a green fluorescent protein (GFP)-fusion. In these cells, round structures positive for both anti-pS409/410 and anti-Ub are observed. These results suggest that intracellular localization of TDP-43, truncation of TDP-43 and proteasomal dysfunction of cells may be involved in the pathological process of TDP-43 proteinopathies. We also found that two small compounds that have been reported to be beneficial in phase II clinical trials of Alzheimer's disease, inhibited the formation of TDP-43 aggregates in these two cellular models, suggesting that these compounds may be effective for the treatment of ALS and FTLD-U.

Methylene blue and dimebon inhibit aggregation of TDP-43 in cellular models

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) are major neurodegenerative diseases with TDP-43 pathology. Here we investigated the effects of methylene blue (MB) and dimebon, two compounds that have been reported to be beneficial in phase II clinical trials of Alzheimer's disease (AD), on the formation of TDP-43 aggregates in SH-SY5Y cells. Following treatment with 0.05 microM MB or 5 microM dimebon, the number of TDP-43 aggregates was reduced by 50% and 45%, respectively. The combined use of MB and dimebon resulted in a 80% reduction in the number. These findings were confirmed by immunoblot analysis. The results indicate that MB and dimebon may be useful for the treatment of ALS, FTLD-U and other TDP-43 proteinopathies.

Truncation and pathogenic mutations facilitate the formation of intracellular aggregates of TDP-43

TAR DNA binding protein of 43 kDa (TDP-43) is a major component of the ubiquitin-positive inclusions found in the brain of patients with frontotemporal lobar degeneration (FTLD-U) and amyotrophic lateral sclerosis (ALS). Here, we report that expression of TDP-43 C-terminal fragments as green fluorescent protein (GFP) fusions in SH-SY5Y cells results in the formation of abnormally phosphorylated and ubiquitinated inclusions that are similar to those found in FTLD-U and ALS. Co-expression of DsRed-tagged full-length TDP-43 with GFP-tagged C-terminal fragments of TDP-43 causes formation of cytoplasmic inclusions positive for both GFP and DsRed. Cells with GFP and DsRed positive inclusions lack normal nuclear staining for endogenous TDP-43. These results suggest that GFP-tagged C-terminal fragments of TDP-43 are bound not only to transfected DsRed-full-length TDP-43 but also to endogenous TDP-43. Endogenous TDP-43 may be recruited to cytoplasmic aggregates of TDP-43 C-terminal fragments, which results in the failure of its nuclear localization and function. Interestingly, expression of GFP-tagged TDP-43 C-terminal fragments harboring pathogenic mutations that cause ALS significantly enhances the formation of inclusions. We also identified cleavage sites of TDP-43 C-terminal fragments deposited in the FTLD-U brains using mass spectrometric analyses. We propose that generation and aggregation of phosphorylated C-terminal fragments of TDP-43 play a primary role in the formation of inclusions and resultant loss of normal TDP-43 localization, leading to neuronal degeneration in TDP-43 proteinopathy.

Expression of reticulon 3 in Alzheimer's disease brain

AIMS

Reticulon 3 (RTN3), a member of the reticulon family of proteins, interacts with the beta-secretase, beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1), and inhibits its activity to produce beta-amyloid protein. The aim of the present study was to clarify the biological role of RTN3 in the brain and its potential involvement in the neuropathology of Alzheimer's disease (AD).

METHODS

We performed immunohistochemical and biochemical analyses using a specific antibody against RTN3 to investigate the expression and subcellular localization of RTN3 in control and AD brain tissue samples.

RESULTS

Western blot analysis revealed no significant differences in the RTN3 levels between control and AD brains. Immunohistochemical staining showed that RTN3 immunoreactivity was predominantly localized in pyramidal neurones of the cerebral cortex. The patterns of RTN3 immunostaining were similar in control and AD cerebral cortices, and senile plaques were generally negative for RTN3. Biochemical subcellular fractionation disclosed that RTN3 colocalized with BACE1 in various fractions, including the endoplasmic reticulum and the Golgi apparatus. Double-immunofluorescence staining additionally indicated that RTN3 was localized in both endoplasmic reticulum and Golgi compartments in neurones.

CONCLUSIONS

These results show that RTN3 is primarily expressed in pyramidal neurones of the human cerebral cortex and that no clear difference of RTN3 immunoreactivity is observable between control and AD brains. Our data also suggest that there is considerable colocalization of RTN3 with BACE1 at a subcellular level.

[Significance of the TDP-43 deposition in FTLD-U and ALS]

Tau-negative and ubiquitin-positive inclusions (UPI) are the pathological hallmarks of frontotemporal lobar degeneration (FTLD-U) and amyotrophic lateral sclerosis (ALS). Recently, TDP-43, a heterogeneous nuclear ribonucleoprotein was identified as a component of these UPI. However, it remains to be determined whether TDP-43 is the major component of UPI, because only antibodies recognizing both normal and abnormal TDP-43 have been available. We raised antibodies to phosphopeptides representing 36 out of 64 candidate phosphorylation sites of human TDP-43. Of the generated antibodies, pS379, pS403/404, pS409, pS410 and pS409/410 clearly labeled UPI and glial cytoplasmic inclusions but not the nuclei. Immunoblot analyses of sarkosyl insoluble fractions demonstrated that the phosphorylation-specific antibodies recognized TDP-43 at -45 kDa, smearing substances and the -25 kDa fragment, all of which were present in the brains of FTLD-U and ALS but not controls. These antibodies did not recognize normal TDP-43 at 43 kDa. These results clearly indicate that abnormally phosphorylated full-length TDP-43 and the C-terminal fragments are the major component of UPI in FTLD-U and ALS. These findings together with recent discovery of mutations in the TDP-43 gene in ALS strongly suggest that TDP-43 is the

Identification of casein kinase-1 phosphorylation sites on TDP-43

TAR DNA-binding protein of 43 kDa (TDP-43) is deposited as hyperphosphorylated cytoplasmic and intranuclear inclusions in brains of patients with frontotemporal lobar degeneration with ubiquitinated inclusions and amyotrophic lateral sclerosis. In this study, we identified 29 phosphorylation sites on recombinant TDP-43 that are phosphorylated by casein kinase-1 (CK1). Interestingly, 18 of them were located in the C-terminal glycine-rich region of TDP-43. Our results indicate that CK1-mediated phosphorylation may play a role in the pathogenesis of these diseases.

[Frontotemporal dementia (FTD) and genetic mutations including progranulin gene]

Research on familial frontotemporal lobar degeneration (FTLD) has led to the discovery of disease-causing genes: microtubule-associated protein tau (MAPT), progranulin (PGRN) and valosin-containing protein (VCP). TAR DNA-binding protein of 43 kDa (TDP-43) has been identified as a major component of tau-negative ubiquitin-positive inclusions in familial and sporadic FTLD and amyotrophic lateral sclerosis (ALS), which are now referred to as TDP-43 proteinopathy. Recent findings of mutations in TDP-43 gene in familial and sporadic ALS cases confirm the pathogenetic role for TDP-43 in neurodegeneration. TDP-43 proteinopathies have been classified into 4 pathological subtypes. Type 1 is characterized by numerous dystrophic neurites (DNs), Type 2 has numerous neuronal cytoplasmic inclusions (NCIs), Type 3 has NCIs and DNs and Type 4 has neuronal intranuclear inclusions (NIIs) and DNs. There is a close relationship between such pathological subtypes of TDP-43 proteinopathy and the immunoblot pattern of C-terminal fragments of accumulated TDP-43. These results parallel our earlier findings of differing C-terminal tau fragments in progressive supranuclear palsy and corticobasal degeneration, despite identical composition of tau isoforms. Taken together, these results suggest that elucidating the mechanism of C-terminal fragment origination may shed light on the pathogenesis of several neurodegenerative disorders involving TDP-43 proteinopathy and tauopathy.