Oligomeric forms of amyloid-β peptide (Aβ) are thought to play a pivotal role in the pathogenesis of Alzheimer's disease (AD), but the mechanism involved is still unclear. Here, we generated induced pluripotent stem cells (iPSCs) from familial and sporadic AD patients and differentiated them into neural cells. Aβ oligomers accumulated in iPSC-derived neurons and astrocytes in cells from patients with a familial amyloid precursor protein (APP)-E693Δ mutation and sporadic AD, leading to endoplasmic reticulum (ER) and oxidative stress. The accumulated Aβ oligomers were not proteolytically resistant, and docosahexaenoic acid (DHA) treatment alleviated the stress responses in the AD neural cells. Differential manifestation of ER stress and DHA responsiveness may help explain variable clinical results obtained with the use of DHA treatment and suggests that DHA may in fact be effective for a subset of patients. It also illustrates how patient-specific iPSCs can be useful for analyzing AD pathogenesis and evaluating drugs.

Background:The inhibitory mechanism of A␤42 aggregation by flavonoid is fully unknown. Results: The oxidant enhanced the inhibitory activity of (ϩ)-taxifolin against A␤42 aggregation by forming A␤42-taxifolin adducts between the Lys residues and oxidized (ϩ)-taxifolin. Conclusion:The inhibitory activity of catechol-type flavonoids requires autoxidation to form an o-quinone to react with Lys. Significance: These may help design promising inhibitors against A␤42 aggregation for Alzheimer disease therapy.

Amyloid fibrils in Alzheimer's disease mainly consist of 40-and 42-mer ␤-amyloid peptides (A␤40 and A␤42) that exhibit aggregative ability and neurotoxicity. Although the aggregates of A␤ peptides are rich in intermolecular ␤-sheet, the precise secondary structure of A␤ in the aggregates remains unclear. To identify the amino acid residues involved in the ␤-sheet formation, 34 proline-substituted mutants of A␤42 were synthesized and their aggregative ability and neurotoxicity on PC12 cells were examined. Prolines are rarely present in ␤-sheet, whereas they are easily accommodated in ␤-turn as a Pro-X corner. Among the mutants at positions 15-32, only E22P-A␤42 extensively aggregated with stronger neurotoxicity than wild-type A␤42, suggesting that the residues at positions 15-21 and 24 -32 are involved in the ␤-sheet and that the turn at positions 22 and 23 plays a crucial role in the aggregation and neurotoxicity of A␤42. The C-terminal proline mutants (A42P-, I41P-, and V40P-A␤42) hardly aggregated with extremely weak cytotoxicity, whereas the C-terminal threonine mutants (A42T-and I41T-A␤42) aggregated potently with significant cytotoxicity. These results indicate that the hydrophobicity of the C-terminal two residues of A␤42 is not related to its aggregative ability and neurotoxicity, rather the C-terminal three residues adopt the ␤-sheet. These results demonstrate well the large difference in aggregative ability and neurotoxicity between A␤42 and A␤40. In contrast, the proline mutants at the N-terminal 13 residues showed potent aggregative ability and neurotoxicity similar to those of wild-type A␤42. The identification of the ␤-sheet region of A␤42 is a basis for designing new aggregation inhibitors of A␤ peptides. Alzheimer's disease (AD)1 is neuropathologically characterized by the progressive deposition of amyloid fibrils in the brain parenchyma and cortical blood vessels (1). This deposition mainly consists of 40-and 42-mer peptides (A␤40 and A␤42) generated from amyloid precursor protein by two proteases, ␤-and ␥-secretase (2, 3). A␤42 plays a pivotal role in the pathogenesis of AD, because the aggregative ability and neurotoxicity of A␤42 are considerably higher than those of A␤40 (4). Because the aggregative ability of A␤ peptides is closely related to the neurotoxicity, precise structural information for amyloid fibrils is indispensable for understanding the molecular mechanisms of AD and related folding diseases and for developing new medicinal leads using the inhibitory activity of amyloid fibril formation.Previous studies on A␤ fibrils showed that A␤ aggregates mainly consist of intermolecular parallel ␤-sheet (5-10

Stomata are composed of a pair of guard cells and a pore between them, and their density and positions are regulated by developmental and environmental signals. In a screen in which we overexpressed many genes coding for putative secretory proteins one by one in Arabidopsis, we identified a gene named STOMAGEN, which increases stomatal density when overexpressed. The STOMAGEN gene encodes a small peptide with a putative secretory signal sequence at its N-terminus and is expressed preferentially in mesophyll cells. This peptide belongs to the EPIDERMAL PATTERNING FACTOR (EPF) family of the cysteine-rich peptides superfamily. The mature form was a 45-amino-acid peptide (stomagen) with three intramolecular disulfide bonds. Stomagen treatment at very low concentrations, as low as 10 nM, increased the stomatal density of wild-type Arabidopsis plants. We propose that stomagen is a mesophyll-to-epidermis signaling molecule that positively regulates stomatal density. We also suggest that stomagen increases stomatal density by competing with negative regulators EPF1 and EPF2 for the receptor-like protein TOO MANY MOUTHS.

Cerebral amyloid angiopathy (CAA) due to ␤-amyloid (A␤) is one of the specific pathological features of familial Alzheimer's disease. A␤ mainly consisting of 40-and 42-mer peptides (A␤40 and A␤42) exhibits neurotoxicity and aggregative abilities. All of the variants of A␤40 and A␤42 found in CAA were synthesized in a highly pure form and examined for neurotoxicity in PC12 cells and aggregative ability. All of the A␤40 mutants at positions 22 and 23 showed stronger neurotoxicity than wild-type A␤40. Similar tendency was observed for A␤42 mutants at positions 22 and 23 whose neurotoxicity was 50 -200 times stronger than that of the corresponding A␤40 mutants, suggesting that these A␤42 mutants are mainly involved in the pathogenesis of CAA. Although the aggregation of E22G-A␤42 and D23N-A␤42 was similar to that of wild-type A␤42, E22Q-A␤42 and E22K-A␤42 aggregated extensively, supporting the clinical evidence that Dutch and Italian patients are diagnosed as hereditary cerebral hemorrhage with amyloidosis. In contrast, A21G mutation needs alternative explanation with the exception of physicochemical properties of A␤ mutants. Attenuated total reflection-Fourier transform infrared spectroscopy spectra suggested that ␤-sheet content of the A␤ mutants correlates with their aggregation. However, ␤-turn is also a critical secondary structure because residues at positions 22 and 23 that preferably form two-residue ␤-turn significantly enhanced the aggregative ability. Alzheimer's disease (AD)1 is neuropathologically characterized by the progressive deposition of amyloid in the brain parenchyma and cortical blood vessels (1). This deposition mainly consists of 40-and 42-mer ␤-amyloid peptides (A␤40 and A␤42) generated from amyloid precursor protein by two proteases, ␤-and ␥-secretases (2, 3). Cerebral amyloid angiopathy (CAA) in familial Alzheimer's disease is linked to missense mutations inside the A␤-coding region in the amyloid precursor protein. The mutations of A␤ sequence are concentrated at positions 21-23 and are called Flemish (A21G) (4), Arctic (E22G) (5, 6), Dutch (E22Q) (7), Italian (E22K) (8), and Iowa (D23N) (9) mutations. These A␤ mutant peptides may play a pathological role in the CAAs because wild-type A␤ peptides induce neuronal death in vitro (10). Neurotoxicity and formation of amyloid fibrils of some CAA-related A␤40 mutants have been independently reported by several groups (11-15). However, there are no reports on the neurotoxicity and aggregation of the CAA-related A␤42 mutants with the exception of Dutch mutation (E22Q) (11), the investigation of which is essential to reveal the mechanism of CAA because wild-type A␤42 shows considerably stronger neurotoxicity and aggregative ability than wild-type A␤40 (11). Moreover, it is indispensable to simultaneously compare neurotoxicity and aggregative ability of all of the CAA-related A␤40 and A␤42 mutants in the same conditions such as pH, peptide concentration, reaction buffer, and temperature.It is difficult to synthesize A␤42 with 14 hydrophobic and/or ...

Oxidative stress is closely linked to the pathogenesis of neurodegeneration. Soluble amyloid ␤ (A␤) oligomers cause cognitive impairment and synaptic dysfunction in Alzheimer disease (AD). However, the relationship between oligomers, oxidative stress, and their localization during disease progression is uncertain. Our previous study demonstrated that mice deficient in cytoplasmic copper/zinc superoxide dismutase (CuZn-SOD, SOD1) have features of drusen formation, a hallmark of agerelated macular degeneration (Imamura, Y., Noda, S., Hashizume, K., Shinoda, K., Yamaguchi, M., Uchiyama, S., Shimizu, T., Mizushima, Y., Shirasawa, T., and Tsubota, K. (2006) Proc. Natl. Acad. Sci. U.S.A. 103, 11282-11287). Amyloid assembly has been implicated as a common mechanism of plaque and drusen formation. Here, we show that Sod1 deficiency in an amyloid precursor protein-overexpressing mouse model (AD mouse, Tg2576) accelerated A␤ oligomerization and memory impairment as compared with control AD mouse and that these phenomena were basically mediated by oxidative damage. The increased plaque and neuronal inflammation were accompanied by the generation of N ⑀ -carboxymethyl lysine in advanced glycation end products, a rapid marker of oxidative damage, induced by Sod1 gene-dependent reduction. The Sod1 deletion also caused Tau phosphorylation and the lower levels of synaptophysin. Furthermore, the levels of SOD1 were significantly decreased in human AD patients rather than non-AD agematched individuals, but mitochondrial SOD (Mn-SOD, SOD2) and extracellular SOD (CuZn-SOD, SOD3) were not. These findings suggest that cytoplasmic superoxide radical plays a critical role in the pathogenesis of AD. Activation of Sod1 may be a therapeutic strategy for the inhibition of AD progression. Alzheimer disease (AD)3 is characterized by amyloid deposits in senile plaques mainly consisting of 40-and 42-mer amyloid ␤ proteins (A␤40 and A␤42) (1, 2). These proteins are produced from amyloid precursor protein (APP) by ␤-and ␥-secretases. A␤42 plays a more important role in the pathogenesis of AD than A␤40 because of its greater aggregation propensity and higher neurotoxicity (3). It has been well demonstrated that oxidative stress is a contributing factor to neurodegenerative disease progression (4, 5). A␤-induced neurotoxicity has been linked to oxidative stress via protein radicalization in vitro (6, 7). Soluble oligomeric assemblies (50ϳ60 kDa; e.g. A␤-derived diffusible ligand, A␤ * 56, and globulomer) of A␤ rather than insoluble fibrils are believed to inhibit long term potentiation and induce neuronal loss (8, 9).Many defensive systems protect mammals from oxidative stress caused by reactive oxygen species, including superoxide radicals, hydrogen peroxide, hydroxyl radicals, and singlet oxygen. Superoxide dismutase (SOD) is one of the major antioxidant enzymes that catalyzes the conversion of superoxide radicals to hydrogen peroxide (10). SOD consists of three isozymes: copper/zinc SOD (CuZn-SOD, SOD1), which is localized in the cytosol, nucle...

Amyloid fibrils mainly consist of 40-mer and 42-mer peptides (Abeta40, Abeta42). Abeta42 is believed to play a crucial role in the pathogenesis of Alzheimer's disease because its aggregative ability and neurotoxicity are considerably greater than those of Abeta40. The neurotoxicity of Abeta peptides involving the generation of free radicals is closely related to the S-oxidized radical cation of Met-35. However, the cation's origin and mechanism of stabilization remain unclear. Recently, structural models of fibrillar Abeta42 and Abeta40 based on systematic proline replacement have been proposed by our group [Morimoto, A.; et al. J. Biol. Chem. 2004, 279, 52781] and Wetzel's group [Williams, A. D.; et al. J. Mol. Biol. 2004, 335, 833], respectively. A major difference between these models is that our model of Abeta42 has a C-terminal beta-sheet region. Our biophysical study on Abeta42 using electron spin resonance (ESR) suggests that the S-oxidized radical cation of Met-35 could be generated by the reduction of the tyrosyl radical at Tyr-10 through a turn structure at positions 22 and 23, and stabilized by a C-terminal carboxylate anion through an intramolecular beta-sheet at positions 35-37 and 40-42 to form a C-terminal core that would lead to aggregation. A time-course analysis of the generation of radicals using ESR suggests that stabilization of the radicals by aggregation might be a main reason for the long-lasting oxidative stress of Abeta42. In contrast, the S-oxidized radical cation of Abeta40 is too short-lived to induce potent neurotoxicity because no such stabilization of radicals occurs in Abeta40.

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