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The cellular prion protein, PrPC, is a copper‐binding protein abundantly expressed in the brain, particularly by neurons, and its conformational conversion into the amyloidogenic isoform, PrPSc, plays a key pathogenic role in prion diseases. However, the role of copper binding to PrPC in prion diseases remains unclear. Here, we fed mice with a low‐copper or regular diet and intracerebrally inoculated them with two different mouse‐adapted RML scrapie and BSE prions. Mice with a low‐copper diet developed disease significantly but only slightly later than those with a regular diet after inoculation with BSE prions, but not with RML prions, suggesting that copper could play a minor role in BSE prion pathogenesis, but not in RML prion pathogenesis. We then generated two lines of transgenic mice expressing mouse PrP with copper‐binding histidine (His) residues in the N‐terminal domain replaced with alanine residues, termed TgPrP(5H > A)‐7342/Prnp0/0 and TgPrP(5H > A)‐7524/Prnp0/0 mice, and similarly inoculated RML and BSE prions into them. Due to 2‐fold higher expression of PrP(5H > A) than PrPC in wild‐type (WT) mice, TgPrP(5H > A)‐7524/Prnp0/0 mice were highly susceptible to these prions, compared to WT mice. However, TgPrP(5H > A)‐7342/Prnp0/0 mice, which express PrP(5H > A) 1.2‐fold as high as PrPC in WT mice, succumbed to disease slightly, but not significantly, later than WT mice after inoculation with RML prions, but significantly so after inoculation with BSE prions. Subsequent secondary inoculation experiments revealed that amino acid sequence differences between PrP(5H > A) and WT PrPSc created no prion transmission barrier to BSE prions. These results suggest that copper‐binding His residues in PrPC are dispensable for RML prion pathogenesis but have a minor effect on BSE prion pathogenesis. Taken together, our current results suggest that copper could have a minor effect on prion pathogenesis in a strain‐dependent manner through binding to His residues in the N‐terminal domain of PrPC. [ABSTRACT FROM AUTHOR]

A comprehensive study is described on the ability to produce radicals, neurotoxicity, and aggregative ability of a series of Abeta42 mutants altered at positions 10,22,35, and 42. The results led to propose a new model for the aggregation of Abeta42 that can explain the mechanism behind the stabilization of the S-oxidized radical carbon of Met-35.

Abstract Background Prion diseases are fatal neurodegenerative disorders that accompany an accumulation of the disease-associated form(s) of prion protein (PrPSc) in the central nervous system. The neuropathological changes in the brain begin with focal deposits of PrPSc, followed by pathomorphological abnormalities of axon terminal degeneration, synaptic loss, atrophy of dendritic trees, and eventual neuronal cell death in the lesions. However, the underlying molecular basis for these neuropathogenic abnormalities is not fully understood. Results In a proteomic analysis of soluble proteins in the brains of mice challenged intracerebrally with scrapie prion (Obihiro I strain), we found that the amount of the full-length form of collapsin response mediator protein-2 (CRMP-2; 61 kDa) decreased in the late stages of the disease, while the amount of its truncated form (56 kDa) increased to comparable levels observed for the full-length form. Detailed analysis by liquid chromatography-electrospray ionization-tandem mass spectrometry showed that the 56-kDa form (named CRMP-2-ΔC) lacked the sequence from serine518 to the C-terminus, including the C-terminal phosphorylation sites important for the regulation of axonal growth and axon-dendrite specification in developing neurons. The invariable size of the mRNA transcript in Northern blot analysis suggested that the truncation was due to post-translational proteolysis. By overexpression of CRMP-2-ΔC in primary cultured neurons, we observed the augmentation of the development of neurite branch tips to the same levels as for CRMP-2T514A/T555A, a non-phosphorylated mimic of the full-length protein. This suggests that the increased level of CRMP-2-ΔC in the brain modulates the integrity of neurons, and may be involved in the pathogenesis of the neuronal abnormalities observed in the late stages of the disease. Conclusions We identified the presence of CRMP-2-ΔC in the brain of a murine model of prion disease. Of note, C-terminal truncations of CRMP-2 have been recently observed in models for neurodegenerative disorders such as ischemia, traumatic brain injury, and Wallerian degeneration. While the structural identity of CRMP-2-ΔC in those models remains unknown, the present study should provide clues to the molecular pathology of degenerating neurons in prion diseases in connection with other neurodegenerative disorders.

Double electron-electron resonance (DEER) has enabled the observation of long-range dipole interactions between electron spin centers and has become a unique method for structural analysis of site-directed spin-labeled (SDSL) proteins. DEER measurements of the oocytes, into which SDL-ubiquitin derivates are injected, have given rise to interpretable signals and have performed in situ analyses of the interspin distances of the proteins.

The article presents a structural analysis of the phototactic transducer protein HtrII linker region from Natronomonas pharaonis. The [alpha]-helix is found to act as an efficient mechanical joint between the HAMP domains.

A photoinduced analogue of the thermal Orton rearrangement reaction by which an N-chlorine atom from a side amino group is transferred to a phenyl ring is analyzed in the solid state. Based on the change of the crystal structure and the physicochemical data, a three-center five-atom mechanism involving homolytic cleavage of the N-Cl bond followed by hydrogen abstraction by the carbonyl group is indicated for the solid-state photoinduced Orton rearrangement.

The photochemical conversion of 1,8a‐dihydroazulene‐1,1‐dicarbonitrile (DHA) to vinylheptafulvene (VHF) is a positive T‐type photoswitch that is well understood in solution, but has not been explored in the solid state. Upon excitation with UV light, DHA is converted into VHF in the solid state, with a distinct color change from yellow to deep‐red, and retention of crystallinity. The structure of the ring‐opened product was assigned to syn‐VHF using variable‐temperature infrared spectroscopy, and determined by X‐ray photodiffraction in a crystal enriched with the product by two‐photon excitation. A radical pathway becomes an observable photoreaction channel at low temperatures, and includes a strongly colored, short‐lived diradical intermediate. True colors: Crystals of dihydroazulene can be reversibly switched between closed and open forms with a distinct color change from yellow to deep‐red. In addition to the closed‐shell ring‐opening reaction, a radical pathway becomes dominant at low temperatures, and includes a strongly colored, short‐lived diradical intermediate. [ABSTRACT FROM AUTHOR]

Investigates the electron spin echo envelope modulation spectra of the reduced primary acceptor quinone, Q[sub A] in preparations of plant photosystems. Substitution of the ferric ion in the quinone-ion complex; Similarity of structure of the binding site of Q[sub A]; Contribution of nitrogen nuclei to the spectra.

Examines the use pulsed electron-electron double resonance and electron spin echo (ESE) methods to measure dipole interaction between paramagnetic centers. Generation of the electron transfer chain structural information in photosystem II (PSII); Orientation of the PSII membranes; Oscillation types in the ESE system.

The cellular prion protein, designated PrPC, is a membrane glycoprotein expressed abundantly in brains and to a lesser extent in other tissues. Conformational conversion of PrPC into the amyloidogenic isoform is a key pathogenic event in prion diseases. However, the physiological functions of PrPC remain largely unknown, particularly in non-neuronal tissues. Here, we show that PrPC is expressed in lung epithelial cells, including alveolar type 1 and 2 cells and bronchiolar Clara cells. Compared with wild-type (WT) mice, PrPC-null mice (Prnp0/0) were highly susceptible to influenza A viruses (IAVs), with higher mortality. Infected Prnp0/0 lungs were severely injured, with higher inflammation and higher apoptosis of epithelial cells, and contained higher reactive oxygen species (ROS) than control WT lungs. Treatment with a ROS scavenger or an inhibitor of xanthine oxidase (XO), a major ROS-generating enzyme in IAV-infected lungs, rescued Prnp0/0 mice from the lethal infection with IAV. Moreover, Prnp0/0 mice transgenic for PrP with a deletion of the Cu-binding octapeptide repeat (OR) region, Tg(PrPΔOR)/Prnp0/0 mice, were also highly susceptible to IAV infection. These results indicate that PrPC has a protective role against lethal infection with IAVs through the Cu-binding OR region by reducing ROS in infected lungs. Cu content and the activity of anti-oxidant enzyme Cu/Zn-dependent superoxide dismutase, SOD1, were lower in Prnp0/0 and Tg(PrPΔOR)/Prnp0/0 lungs than in WT lungs. It is thus conceivable that PrPC functions to maintain Cu content and regulate SOD1 through the OR region in lungs, thereby reducing ROS in IAV-infected lungs and eventually protecting them from lethal infection with IAVs. Our current results highlight the role of PrPC in protection against IAV infection, and suggest that PrPC might be a novel target molecule for anti-influenza therapeutics. [ABSTRACT FROM AUTHOR]

Prion diseases are a group of fatal neurodegenerative disorders caused by prions, which consist mainly of the abnormally folded isoform of prion protein, PrPSc. A pivotal pathogenic event in prion disease is progressive accumulation of prions, or PrPSc, in brains through constitutive conformational conversion of the cellular prion protein, PrPC, into PrPSc. However, the cellular mechanism by which PrPSc is progressively accumulated in prion-infected neurons remains unknown. Here, we show that PrPSc is progressively accumulated in prion-infected cells through degradation of the VPS10P sorting receptor sortilin. We first show that sortilin interacts with PrPC and PrPSc and sorts them to lysosomes for degradation. Consistently, sortilin-knockdown increased PrPSc accumulation in prion-infected cells. In contrast, overexpression of sortilin reduced PrPSc accumulation in prion-infected cells. These results indicate that sortilin negatively regulates PrPSc accumulation in prion-infected cells. The negative role of sortilin in PrPSc accumulation was further confirmed in sortilin-knockout mice infected with prions. The infected mice had accelerated prion disease with early accumulation of PrPSc in their brains. Interestingly, sortilin was reduced in prion-infected cells and mouse brains. Treatment of prion-infected cells with lysosomal inhibitors, but not proteasomal inhibitors, increased the levels of sortilin. Moreover, sortilin was reduced following PrPSc becoming detectable in cells after infection with prions. These results indicate that PrPSc accumulation stimulates sortilin degradation in lysosomes. Taken together, these results show that PrPSc accumulation of itself could impair the sortilin-mediated sorting of PrPC and PrPSc to lysosomes for degradation by stimulating lysosomal degradation of sortilin, eventually leading to progressive accumulation of PrPSc in prion-infected cells. [ABSTRACT FROM AUTHOR]

We investigated the scavenging activities of methanol-extracted oil and the distribution of paramagnetic species inZanthoxylum limonella(ZL) seeds using noninvasive 9 GHz electron paramagnetic resonance (EPR) imaging and continuous wave EPR. EPR detected three different stable paramagnetic species that were assigned to stable organic radicals, Mn2+, and other paramagnetic metal complexes. Two-dimensional EPR imaging showed that the stable paramagnetic species were located in the pigmented seed region with a strong intensity. Gas chromatography–mass spectrophotometric (GC–MS) analyses were then performed to identify the compound possibly related to the scavenging activity. The DPPH scavenging activities of ZL were slightly higher than those ofPiper nigrumandCoriandrum sativum. Based on the results of EPR, GC–MS, and other methods, limonene in ZL is one of the major compounds that can be related to the scavenging activities. [ABSTRACT FROM PUBLISHER]

One of the most inevitable limitations of any material that is exposed to mechanical impact is that they are inexorably prone to mechanical damage, such as cracking, denting, gouging, or wearing. To confront this challenge, the field of polymers has developed materials that are capable of autonomous self-healing and recover their macroscopic integrity similar to biological organisms. However, the study of this phenomenon has mostly remained within the soft materials community and has not been explored by solid-state organic chemists. The first evidence of self-healing in a molecular crystal is now presented using crystals of dipyrazolethiuram disulfide. The crystals were mildly compressed and the degree of healing was found to be 6.7 %. These findings show that the self-healing properties can be extended beyond mesophasic materials and applied towards the realm of ordered solid-state compounds. [ABSTRACT FROM AUTHOR]

We investigated the antioxidant activities and locations of stable paramagnetic species in dry (or drying) shiitake mushroom (Lentinus edodes) using continuous wave (CW) electron paramagnetic resonance (EPR) and 9 GHz EPR imaging. CW 9 GHz EPR detected paramagnetic species (peak-to-peak linewidth (ΔHpp) = 0.57 mT) in the mushroom. Two-dimensional imaging of the sharp line using a 9 GHz EPR imager showed that the species were located in the cap and shortened stem portions of the mushroom. No other location of the species was found in the mushroom. However, radical locations and concentrations varied along the cap of the mushroom. The 9 GHz EPR imaging determined the exact location of stable paramagnetic species in the shiitake mushroom. Distilled water extracts of the pigmented cap surface and the inner cap of the mushroom showed similar antioxidant activities that reduced an aqueous solution of 0.1 mM 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl. The present results suggest that the antioxidant activities of the edible mushroom extracts are much weaker than those of ascorbic acid. Thus, CW EPR and EPR imaging revealed the location and distribution of stable paramagnetic species and the antioxidant activities in the shiitake mushroom for the first time. [ABSTRACT FROM PUBLISHER]