Volume 6, Number 5, October 2004

Pages 461-467
Mar Pérez, Raquel Cuadros, María J. Benítez, Juan S. Jiménez (communicated by Jesus Avila)
Interaction of Alzheimer’s disease amyloid ß peptide fragment 25-35 with tau protein, and with a tau peptide containing the microtubule binding domain
Abstract: The interaction of amyloid ß (Aß) 25-35 with tau protein and with the peptide 1/2R (KVTSKCGSLGNIHHKPGGG), has been investigated by chromatography, electron microscopy, and surface plasmon resonance (SPR). Aß 25-35 comprises the minimum region of Aß peptide that is able to aggregate into fibrils, and 1/2R contains residues 307-325 from the tau region involved in microtubule binding. The results of chromatography showed that Aß 25-35 induces the aggregation of tau protein and of tau peptide 1/2R. Likewise, the results of electron microscopy showed that Aß 25-35 increases the tau peptide polymerization observed in the presence of polyanions like heparin. A decrease in Aß 25-35 aggregation induced by tau peptide was also observed by both techniques. No direct interaction between tau protein immobilized on the sensor surface and Aß25-35 could be detected by SPR. However, incubation of tau protein at room temperature produced the loss of capability of this protein for interacting with the active biosensor surface. The presence of Aß 25-35 during the incubation of tau protein makes more efficient this loss of interacting capability with the sensor surface. These results clearly indicate that Aß 25-35, the peptide region to which the cytotoxic properties of Aß can be assigned, interacts with the peptide region of tau protein involved in microtubule binding. This interaction produces the aggregation of tau peptide and the concomitant disassembling of Aß 25-35, offering thus an explanation to the lack of co-localization of neurofibrillary tangles and senile plaques in Alzheimer’s disease, and suggesting the possibility that tau protein may have a protective action by preventing Aß from adopting the cytotoxic, aggregated form.

Pages 469-474
Jack van Horssen, Rob A.I. de Vos, Ernst N.H. Jansen Steur, Guido David, Pieter Wesseling, Robert M.W. de Waal, Marcel M. Verbeek
Absence of heparan sulfate proteoglycans in Lewy bodies and Lewy neurites in Parkinson’s disease brains
Abstract: Alpha-Synuclein is the major constituent of Lewy bodies and Lewy neurites in Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Relatively little is known about the exact mechanism of alpha-synuclein deposition and fibrillization in these alpha-synucleinopathies. In order to better understand the pathogenesis of alpha-synucleinopathies it is important to identify molecules that regulate the fibrillization of alpha-synuclein. Since it has been demonstrated that heparan sulfate proteoglycans (HSPGs) and glycosaminoglycans (GAGs) promote the conversion of non-fibrillar amyloid ß-protein (Aß) into neurotoxic fibrillar Aß in Alzheimer’s disease, they might also be involved in alpha-synuclein aggregation. It was the aim of our study to examine the distribution pattern of these macromolecules in PD brains and the possible association with Lewy bodies and Lewy neurites. Although HSPGs clearly colocalized with senile plaques, we were unable to identify HSPGs or GAGs in Lewy bodies and Lewy neurites and therefore concluded that it is likely that alpha-synuclein fibrillization and stabilization occurs independently of the presence of HSPGs or GAGs.

Pages 475-482
Manuel Menéndez
Pathological and clinical heterogeneity of presenilin 1 gene mutations
Abstract: The presenilins are two closely related genes which implication in familial Alzheimer’s disease (FAD) is well known. Presenilin 1 gene (PS1) mutations cause heterogeneous disorders and a bibliographical review of atypical PS1-FAD cases allows us to describe a great diversity of neuropathological and clinical variations and conclude that most of them do not strongly depend on the genetic location of the mutation so other genetic or epigenetic factors may be involved.

Pages 483-488
Hideo Hara, Alon Monsonego, Katsutoshi Yuasa, Kayo Adachi, Xiao Xiao, Shin’ichi Takeda, Keikichi Takahashi, Howard L. Weiner, Takeshi Tabira
Development of a safe oral Aß vaccine using recombinant adeno-associated virus vector for Alzheimer’s disease.
Abstract: A new oral vaccine for Alzheimer's disease was developed using recombinant adeno-associated virus vector carrying Aß cDNA (AAV/Aß). Oral administration of the vaccine without adjuvant induced the expression and secretion of Aß1-43 or Aß1-21 in the epithelial cell layer of the intestine in amyloid precursor protein transgenic mice. Serum antibody levels were elevated for more than six months, while T cell proliferative responses to Aß was not detected. Brain Aß burden was significantly decreased compared to the control without inflammatory changes. This oral AAV/Aß vaccine seems to be promising for prevention and treatment of Alzheimer’s disease.

Pages 489-495
Laura A. Robertson, Kenneth L. Moya, Kieran C. Breen
The potential role of tau protein O-glycosylation in Alzheimer’s disease
Abstract: Single O-linked N-acetylglucosamine (O-GlcNAc) sugar residues have been can compete with phosphate groups to occupy specific sites on certain nuclear and cytosolic proteins. Here we show that inhibiting cellular kinase activities resulted in changes in protein O-glycosylation levels in heat-stable cytoskeletal protein fractions derived from primary neuronal cells. As increased phosphorylation of the microtubule-associated protein tau is one of the pathological hallmarks of Alzheimer’s disease, glycosylation may play an influential role in this process. We observed a significant decrease in the protein O-GlcNAc glycosylation of a tau-enriched cytoskeletal fraction generated from AD post-mortem brain samples as compared with control, suggesting an inverse relationship between the two post-translational modifications. Finally, cells transfected with the cDNA coding for O-GlcNAc transferase (OGT) displayed altered tau phosphorylation patterns as compared with control cells, suggesting that changes in tau glycosylation may influence its phosphorylation state. The specificity of the changes in the phosphorylation of individual amino acid residues provides evidence for a targeted O-glycosylation of tau.

Pages 497-501
Liat Ben-Avi, Ronen Durst, Shoshi Shpitzen, Eran Leitersdorf, Vardiella Meiner
Apo E genotyping: accurate, simple, high throughput method using ABI Prism® SNaPshot™ Multiplex System
Abstract: Apolipoprotein E (apo E) is an essential constituent of several plasma lipoproteins, and plays an important role in lipoprotein metabolism. The apo E gene exhibits two common functional polymorphisms, producing 3 isoforms known to be associated with the risks of developing cardiovascular disease and susceptibility to Alzheimer’s disease. Numerous different methods have been established for determining the three apo E isoforms, yet there are disadvantages and ambiguities associated with all of them. We used a method adapted for multiplex automated primer extension analysis by improving a commercially available protocol (SNaPshot™) and simultaneously typing apo E single nucleotide polymorphisms (SNPs) encoding for isoforms at codon 112 and 158. This protocol relies on the extension with fluorescent dideoxyNTPs of a primer that ends one nucleotide 5’ of a given SNP (minisequencing). Improvement of the method is achieved by incorporating into the minisequencing reaction two pooled primers corresponding to both apo E SNPs followed by analysis on an ABI PRisMS 310 DNA sequencer. We found full concordance with genotypes determined using universal heteroduplex. This method is readily available for many laboratories and is a simple, unequivocal easy to use technique suitable for large amount of clinical samples that may provide a significant improvement over previously reported methods for apo E genotyping.

Pages 503-508
Thomas A. Ala, Robert C. Doss, Christopher J. Sullivan (Communicated by J. Riley McCarten)
Reversible dementia: A case of cryptococcal meningitis masquerading as Alzheimer’s disease
Abstract: A 70-year-old man presented to us in 1994 with a three-year history of worsening dementia. With the exceptions of a Mini-Mental State exam score of 20 and an inability to tandem walk, his physical and neurological examinations were normal. His past medical history revealed that in 1992 he had been evaluated at another institution for memory impairment and bifrontal headaches. A spinal tap had been done in 1992 showing elevated protein, reduced glucose, and a pleocytosis; his CSF fungal culture and cryptococcal antigen test were negative. He subsequently was lost to follow-up, and although his headaches had resolved, his mental status had continued to worsen. In 1994 his CSF cryptococcal antigen was positive, and his CSF fungal culture grew C. neoformans. He gradually improved with treatment for cryptococcal meningitis (CM). With the exception of mild memory impairment, in 2003 he and his family thought that his mental status had returned to normal. This case emphasizes that: 1) CM should always be kept in the differential diagnosis of dementia; 2) CM may be extremely insidious and difficult to diagnose; and 3) if one is to rule out unequivocally all possible reversible causes of dementia, one should perform a spinal tap.

Pages 509-514
David A. Costa, Lars N.G.Nilsson, Kelly R. Bales, Steven M. Paul, Huntington Potter
Apolipoprotein is required for the formation of filamentous amyloid, but not for amorphous Aß deposition, in an AßPP/PS double transgenic mouse model of Alzheimer’s disease
Abstract: To determine the role of apolipoprotein E (apoE) in the deposition of different forms of Alzheimer amyloid deposit, we studied mice expressing both mutant human amyloid ß-protein precursor (AßPP) and presenilin 1 (PS1) that, in addition, were either normal or knocked-out for apoE. By 7 months of age, extensive deposits of amorphous amyloid ß (Aß) had developed equally in both lines, indicating that, when present in high amounts, Aß alone is sufficient for such deposition to occur. In contrast, filamentous, thioflavine S-positive amyloid deposition in AßPP/PS mice was catalyzed at least 3000 fold by apoE. Electron micrographs further illustrated the filamentous nature of Aß deposits in mice expressing apoE. These and other behavior data indicate that the primary function of apoE in Alzheimer’s disease is to promote the polymerization of Aß into mature, beta pleated sheet filaments, a process that is necessary for inducing cognitive decline. Thus, preventing apoE from binding to Aß may prove to be an effective means of therapeutic intervention.

Pages 515-525
Debra Boyd-Kimball, Rukhsana Sultana, Hafiz Mohmmad-Abdul, D. Allan Butterfield
Rodent Aß(1-42) exhibits oxidative stress properties similar to those of human Aß(1-42): Implications for proposed mechanisms of toxicity
Abstract: Alzheimer’s disease is a neurodegenerative disorder associated with aging and cognitive decline. Amyloid beta peptide (1-42) [Aß(1-42)] is a primary constituent of senile plaques--a hallmark of Alzheimer’s disease--and has been implicated in the pathogenesis of the disease. Previous studies have shown that methionine residue 35 of Aß(1-42) may play a critical role in Aß(1-42)-mediated oxidative stress and neurotoxicity. Several additional mechanisms of neurotoxicity have been proposed, including the role of Cu(II) binding and reduction to produce hydrogen peroxide and the role of peptide aggregation. It has been reported that rodent Aß is less likely to form larger ß-sheet structures, and consequently, large aggregates. As a consequence of the lack of deposition of the peptide in rodent brain, rodent Aß has been proposed to be non-toxic. Additionally, the sequence of the rodent variety of Aß(1-42) contains three amino acid substitutions compared to the human sequence. These substitutions include the shift of arginine 5, trysosine 10, and histidine 13 to glycine, phenylalanine, and arginine, respectively. This shift in sequence within the Cu(II) binding region of the peptide results in a decrease in the ability of the rodent Aß peptide to reduce Cu(II) to Cu(I) compared to the human Aß peptide. As a result of the effect of the amino acid variations on the ability of the rodent peptide to reduce Cu(II) to Cu(I) compared to the human peptide, the rodent Aß has been proposed to lack oxidative stress properties. In this study, the oxidative stress and neurotoxic properties of rodent Aß(1-42) [Aß1-42)Rat] were evaluated and compared to those of human Aß(1-42). Both human Aß(1-42) and Aß(1-42)Rat were found to have a significant effect on neuronal DNA fragmentation, loss of neuritic networks, and cell viability. Aß(1-42) Rat was found to cause a significant increase in both protein oxidation and lipid peroxidation, similar to Aß(1-42), both of which were inhibited by the lipid-soluble, chain breaking antioxidant vitamin E, suggesting that reactive oxygen species play a role in the Aß-mediated toxicity. Taken together, these results suggest that Cu(II) reduction may not play a critical role in Aß(1-42)Rat-induced oxidative stress, and that the oxidative stress exhibited by this peptide may be a consequence of the presence of methionine 35, similar to the findings associated with the native human Aß(1-42) peptide.

Pages 527-536
LuGuang Luo, Edward G Stopa
Thyrotropin releasing hormone inhibits tau phosphorylation by dual signaling pathways in hippocampal neurons
Abstract: Depletion of thyrotropin releasing hormone (TRH) gene expression resulted in augmented Tau and glycosynthetase kinase-3ß (GSK-3ß), in contrast, TRH administration resulted in decreases of 75% in GSK-3ß and 90% in Tau phosphorylation in cultured rat hippocampal neurons. To further study TRH regulation of tau phosphorylation, immunoblotting was used to explore G-protein coupled TRH receptor activation of the phosphokinase C (PKC) and phosphokinase A (PKA) signaling pathways. TRH was found to rapidly activate PKA (2.5 fold in 10 min) while it suppressed PKC (levels decreased by 85% vs. control) in hippocampal neurons. This process was also discovered to be a cell type-specific response, as TRH activated PKC in only hypothalamic neurons. Further investigation revealed that the Src inhibitor Protein Phosphatase 2 (PP2, 50 uM) could block TRH inhibition of PKC, GSK-3ß, and tau phosphorylation with no effects on PKA. In addition, the PKC inhibitor GF109203 Bis (10 uM) was also able to suppress TRH inhibition of GSK-3ß, leading to increased GSK-3ß activity. Independent of these effects, inhibition of PKA by H89 (10 uM) significantly blocked TRH inhibition of GSK-3ß. These data suggests that both PKA and PKC are independently crucial to TRH’s effects on GSK-3ß, and support the roles of two distinct pathways involving suppression of PKC via the Src kinase and activation of PKA in mediating TRH effects on GSK-3ß and tau. These dual signaling pathways between TRH and tau may provide mechanisms for the precise regulation of tau phosphorylation and dephosphorylation in neurons.

Pages 537-545
Transcript of Live Discussion held at the Alzheimer Research Forum
Axonal Transport Hypothesis Moves on to Implicate Presenilin

Pages 547-568
Proceedings of the 11th International Symposium, “New Frontiers of Neurochemistry and Neurophysics on Diagnosis and Treatment of Neurological Diseases,”
with participation of the International Society for Neurochemistry (ISN), in Memory of Vincenzo Lombardi (Martin, Slovakia, December 4-7, 2003)

Page 569
Book Review:
Psychiatry Highlights 2003-2004 Fast Facts Series by Malcolm Lader. Health Press Ltd., Oxford, UK, 2004, 98 pp. Reviewed by Alexandre de Mendonça.