Mouse alpha-macroglobulin. Structure, function and a molecular model.

Mouse alpha-macroglobulin (M-AMG) is believed to be a functional homologue of human alpha 2-macroglobulin (h-alpha 2M). The subunit composition, the tryptic cleavage pattern before and after methylamine incorporation and the two-dimensional tryptic-peptide mapping, however, indicate that these two proteins are structurally distinct. M-AMG is composed of two major types of polypeptides (Mr 163,000 and 35,000) together with a minor polypeptide (Mr 185,000), whereas h-alpha 2M has only one type of polypeptide (Mr 185,000). After incorporation of methylamine, there is no change in the normal tryptic-cleavage pattern of M-AMG; however, tryptic cleavage of h-alpha 2M is severely retarded [Hudson & Koo (1982) Biochim. Biophys. Acta 704, 290-303]. The N-terminal sequence of the 163,000-Mr polypeptide of M-AMG shows sequence homology with the N-terminal sequence of h-alpha 2M. The amino acid compositions of M-AMG and its two major polypeptide chains are compared. Thermal fragmentation studies show that the 163,000-Mr polypeptide is broken down into 125,000-Mr and 29,000-Mr fragments. Trypsin-binding studies show that M-AMG can bind two molecules of trypsin/molecule. Inactivations of the trypsin-binding property of M-AMG and h-alpha 2M with methylamine show similar kinetics of inhibition at 4 degrees C. A structural model of M-AMG is proposed, based on accumulated data.     

Synthesis of (2R,5S)-dihydroxymethyl-(3R,4R)-dihydroxypyrrolidine (DGDP) via stereoselective amination using chlorosulfonyl isocyanate

A stereoselective approach for synthesizing (2R,5S)-dihydroxymethyl-(3R,4R)-dihydroxypyrrolidine 1 (2,5-dideoxy-2,5-imino-d-glucitol, DGDP) was achieved using a seven-step approach starting from 2,3,4,6-tetra-O-benzyl-d-mannose (7). Key steps for the preparation of the title compound 1 involved the regioselective and diastereoselective amination of the cinnamyl anti-1,2-polybenzyl ethers 5 and 6 using chlorosulfonyl isocyanate (CSI) and ring cyclization to form the pyrrolidine ring. The reaction between anti-1,2-polybenzyl ether 5 and CSI in toluene at 0 degrees C afforded the corresponding anti-1,2-amino alcohol 4 as a major product with a diastereoselectivity of 16:1 in 76% yield. The mechanism underlying these reactions may be explained by the neighboring-group effect leading to the retention of stereochemistry.     

A Survey of the Brassica rapa genome by BAC-end sequence analysis and comparison with Arabidopsis thaliana

Brassica rapa ssp. pekinensis (Chinese cabbage) is an economically important crop and a model plant for studies on polyploidization and phenotypic evolution. To gain an insight into the structure of the B. rapa genome we analyzed 12,017 BAC-end sequences for the presence of transposable elements (TEs), SSRs, centromeric satellite repeats and genes, and similarity to the closely related genome of Arabidopsis thaliana. TEs were estimated to occupy 14% of the genome, with 12.3% of the genome represented by retrotransposons. It was estimated that the B. rapa genome contains 43,000 genes, 1.6 times greater than the genome of A. thaliana. A number of centromeric satellite sequences, representing variations of a 176-bp consensus sequence, were identified. This sequence has undergone rapid evolution within the B. rapa genome and has diverged among the related species of Brassicaceae. A study of SSRs demonstrated a non-random distribution with a greater abundance within predicted intergenic regions. Our results provide an initial characterization of the genome of B. rapa and provide the basis for detailed analysis through whole-genome sequencing.     

Genetic characterization and curation of diploid A-genome wheat species

A-genome diploid wheats represent the earliest domesticated and cultivated wheat species in the Fertile Crescent and include the donor of the wheat A sub-genome. The A-genome species encompass the cultivated einkorn (Triticum monococcum L. subsp. monococcum), wild einkorn (T. monococcum L. subsp. aegilopoides (Link) Thell.), and Triticum urartu. We evaluated the collection of 930 accessions in the Wheat Genetics Resource Center (WGRC) using genotyping by sequencing and identified 13,860 curated single-nucleotide polymorphisms. Genomic analysis detected misclassified and genetically identical (>99%) accessions, with most of the identical accessions originating from the same or nearby locations. About 56% (n = 520) of the WGRC A-genome species collections were genetically identical, supporting the need for genomic characterization for effective curation and maintenance of these collections. Population structure analysis confirmed the morphology-based classifications of the accessions and reflected the species geographic distributions. We also showed that T. urartu is the closest A-genome diploid to the A-subgenome in common wheat (Triticum aestivum L.) through phylogenetic analysis. Population analysis within the wild einkorn group showed three genetically distinct clusters, which corresponded with wild einkorn races α, β, and γ described previously. The T. monococcum genome-wide F_ST scan identified candidate genomic regions harboring a domestication selection signature at the Non-brittle rachis 1 (Btr1) locus on the short arm of chromosome 3A^m at ∼70 Mb. We established an A-genome core set (79 accessions) based on allelic diversity, geographical distribution, and available phenotypic data. The individual species core set maintained at least 79% of allelic variants in the A-genome collection and constituted a valuable genetic resource to improve wheat and domesticated einkorn in breeding programs.

Genotyping diploid A-genome relatives of wheat uncovered high genetic diversity and unique evolutionary relationships giving insight to the effective use of this germplasm for wheat improvement.     

Effects of (−)-Sesamin on Chronic Stress-Induced Anxiety Disorders in Mice

This study investigated the effects of (?)-sesamin on chronic electric footshock (EF) stress-induced anxiety disorders in mice. Mice were treated with (?)-sesamin (25 and 50 mg/kg) orally once a day for 21 days prior to exposure to EF stress (0.6 mA, 1 s every 5 s, 3 min). Mice treated with (?)-sesamin (25 and 50 mg/kg) exhibited less severe decreases in the number of open arm entries and time spent on open arms in the elevated plus-maze test and the distance traveled in the open field test following exposure to chronic EF stress. Similarly, mice treated with (?)-sesamin exhibited significantly less severe decreases in brain levels of dopamine, norepinephrine, and serotonin following exposure to chronic EF stress. Increases in serum levels of corticosterone and expression of c-Fos were also less pronounced in mice treated with (?)-sesamin (25 and 50 mg/kg). These results suggest that (?)-sesamin may protect against the effects of chronic EF stress-induced anxiety disorders by modulating dopamine, norepinephrine, and serotonin levels, c-Fos expression, and corticosterone levels.     

Age-related Differentiation in Newly Generated DCX Immunoreactive Neurons in the Subgranular Zone of the Gerbil Dentate Gyrus

In the present study, we investigated age-related changes of newborn neurons in the gerbil dentate gyrus using doublecortin (DCX), a marker of neuronal progenitors which differentiate into neurons in the brain. In the postnatal month 1 (PM 1) group, DCX immunoreactivity was detected in the subgranular zone of the dentate gyrus, but DCX immunoreactive neurons did not have fully developed processes. Thereafter, DCX immunoreactivity and its protein levels in the dentate gyrus were found to decrease with age. Between PM 3 and PM 18, DCX immunoreactive neuronal progenitors showed well-developed processes which projected to the granular layer of the dentate gyrus, but at PM 24, a few DCX immunoreactive neuronal progenitors were detected in the subgranular zone of the dentate gyrus. DCX protein level in the dentate gyrus at PM 1 was high, thereafter levels of DCX were decreased with time. The authors suggest that a decrease of DCX immunoreactivity and its protein level with age may be associated with aging processes in the hippocampal dentate gyrus.     

Treadmill exercise represses neuronal cell death and inflammation during Aβ-induced ER stress by regulating unfolded protein response in aged presenilin 2 mutant mice

Alzheimer’s disease (AD) is characterized by the deposition of aggregated amyloid-beta (Aβ), which triggers a cellular stress response called the unfolded protein response (UPR). The UPR signaling pathway is a cellular defense system for dealing with the accumulation of misfolded proteins but switches to apoptosis when endoplasmic reticulum (ER) stress is prolonged. ER stress is involved in neurodegenerative diseases including AD, but the molecular mechanisms of neuronal apoptosis and inflammation by Aβ-induced ER stress to exercise training are not fully understood. Here, we demonstrated that treadmill exercise (TE) prevented PS2 mutation-induced memory impairment and reduced Aβ-42 deposition through the inhibition of β-secretase (BACE-1) and its product, C-99 in cortex and/or hippocampus of aged PS2 mutant mice. We also found that TE down-regulated the expression of GRP78/Bip and PDI proteins and inhibited activation of PERK, eIF2α, ATF6α, sXBP1 and JNK-p38 MAPK as well as activation of CHOP, caspase-12 and caspase-3. Moreover, TE up-regulated the expression of Bcl-2 and down-regulated the expressions of Bax in the hippocampus of aged PS2 mutant mice. Finally, the generation of TNFα and IL-1α and the number of TUNEL-positive cells in the hippocampus of aged PS2 mutant mice was also prevented or decreased by TE. These results showed that TE suppressed the activation of UPR signaling pathways as well as inhibited the apoptotic pathways of the UPR and inflammatory response following Aβ-induced ER stress. Thus, therapeutic strategies that modulate Aβ-induced ER stress through TE could represent a promising approach for the prevention or treatment of AD.     

Lipase-catalyzed synthesis of fatty acid sugar ester using extremely supersaturated sugar solution in ionic liquids

Artificial nanotransport systems inspired by intracellular transport processes have been investigated for over a decade using the motor protein kinesin and microtubules. However, only unidirectional cargo transport has been achieved for the purpose of nanotransport in a microfluidic system. Here, we demonstrate bidirectional nanotransport by integrating kinesin and dynein motor proteins. Our molecular system allows microtubule orientation of either polarity in a microfluidic channel to construct a transport track. Each motor protein acts as a nanoactuators that transports microspheres in opposite directions determined by the polarity of the oriented microtubules: kinesin-coated microspheres move toward the plus end of microtubules, whereas dynein-coated microspheres move toward the minus end. We demonstrate both unidirectional and bidirectional transport using kinesin- and dynein-coated microspheres on microtubules oriented and glutaraldehyde-immobilized in a microfluidic channel. Tracking and statistical analysis of microsphere movement demonstrate that 87-98% of microspheres move in the designated direction at a mean velocity of 0.22-0.28 microm/s for kinesin-coated microspheres and 0.34-0.39 microm/s for dynein-coated microspheres. This bidirectional nanotransport goes beyond conventional unidirectional transport to achieve more complex artificial nanotransport in vitro.