Impact of uniaxial strain and doping on oxygen diffusion in CeO2

Doped ceria is an important electrolyte for solid oxide fuel cell applications. Molecular dynamics simulations have been used to investigate the impact of uniaxial strain along the directions and rare-earth doping (Yb, Er, Ho, Dy, Gd, Sm, Nd, and La) on oxygen diffusion. We introduce a new potential model that is able to describe the thermal expansion and elastic properties of ceria to give excellent agreement with experimental data. We calculate the activation energy of oxygen migration in the temperature range 900-1900K for both unstrained and rare-earth doped ceria systems under tensile strain. Uniaxial strain has a considerable effect in lowering the activation energies of oxygen migration. A more pronounced increase in oxygen diffusivities is predicted at the lower end of the temperature range for all the dopants considered

Human ClC-6 Is a Late Endosomal Glycoprotein that Associates with Detergent-Resistant Lipid Domains

BACKGROUND: The mammalian CLC protein family comprises nine members (ClC-1 to -7 and ClC-Ka, -Kb) that function either as plasma membrane chloride channels or as intracellular chloride/proton antiporters, and that sustain a broad spectrum of cellular processes, such as membrane excitability, transepithelial transport, endocytosis and lysosomal degradation. In this study we focus on human ClC-6, which is structurally most related to the late endosomal/lysomal ClC-7. PRINCIPAL FINDINGS: Using a polyclonal affinity-purified antibody directed against a unique epitope in the ClC-6 COOH-terminal tail, we show that human ClC-6, when transfected in COS-1 cells, is N-glycosylated in a region that is evolutionary poorly conserved between mammalian CLC proteins and that is located between the predicted helices K and M. Three asparagine residues (N410, N422 and N432) have been defined by mutagenesis as acceptor sites for N-glycosylation, but only two of the three sites seem to be simultaneously N-glycosylated. In a differentiated human neuroblastoma cell line (SH-SY5Y), endogenous ClC-6 colocalizes with LAMP-1, a late endosomal/lysosomal marker, but not with early/recycling endosomal markers such as EEA-1 and transferrin receptor. In contrast, when transiently expressed in COS-1 or HeLa cells, human ClC-6 mainly overlaps with markers for early/recycling endosomes (transferrin receptor, EEA-1, Rab5, Rab4) and not with late endosomal/lysosomal markers (LAMP-1, Rab7). Analogously, overexpression of human ClC-6 in SH-SY5Y cells also leads to an early/recycling endosomal localization of the exogenously expressed ClC-6 protein. Finally, in transiently transfected COS-1 cells, ClC-6 copurifies with detergent-resistant membrane fractions, suggesting its partitioning in lipid rafts. Mutating a juxtamembrane string of basic amino acids (amino acids 71-75: KKGRR) disturbs the association with detergent-resistant membrane fractions and also affects the segregation of ClC-6 and ClC-7 when cotransfected in COS-1 cells. CONCLUSIONS: We conclude that human ClC-6 is an endosomal glycoprotein that partitions in detergent resistant lipid domains. The differential sorting of endogenous (late endosomal) versus overexpressed (early and recycling endosomal) ClC-6 is reminiscent of that of other late endosomal/lysosomal membrane proteins (e.g. LIMP II), and is consistent with a rate-limiting sorting step for ClC-6 between early endosomes and its final destination in late endosomes

Mesoscale engineering of photonic glass for tunable luminescence

The control of optical behavior of active materials through manipulation of microstructure has led to the development of high-performance photonic devices with enhanced integration density, improved quantum efficiencies and controllable colour output. However, the achievement of robust light-harvesting materials with tunable, broadband and flatten emission remains a long-standing goal, owing to the limited inhomogeneous broadening in ordinary hosts. Here, we describe an effective strategy for management of photon emission by manipulation of mesoscale heterogeneities in optically active materials. Importantly, this unique approach enables control of dopant-dopant and dopant-host interactions at the extended mesoscale. This allows generating intriguing optical phenomena such as high activation ratio of dopant (close to 100 %), dramatically inhomogeneous broadening (up to 480 nm), notable emission enhancement, and moreover, simultaneously extending emission bandwidth and flattening spectral shape in glass and fiber. Our results highlight that the findings connect the understanding and manipulation at the mesoscale realm to functional behavior at the macroscale, and the approach to managing the dopants based on mesoscale engineering may provide new opportunity for construction of robust fiber light source.National Natural Science Foundation of China (Grant IDs: 11474102, 51202180), the Chinese Program for New Century Excellent Talents in University (Grant ID: NCET-13-0221), Guangdong Natural Science Funds for Distinguished Young Scholar (Grant ID: S2013050014549), Fundamental Research Funds for the Central University, Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, World Premier International Research Center Initiative (WPI), MEXT, JapanThis is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Nature Publishing Group

Impairment of chaperone-mediated autophagy leads to selective lysosomal degradation defects in the lysosomal storage disease cystinosis

Metabolite accumulation in lysosomal storage disorders (LSDs) results in impaired cell function and multi-systemic disease. Although substrate reduction and lysosomal overload-decreasing therapies can ameliorate disease progression, the significance of lysosomal overload-independent mechanisms in the development of cellular dysfunction is unknown for most LSDs. Here, we identify a mechanism of impaired chaperone-mediated autophagy (CMA) in cystinosis, a LSD caused by defects in the cystine transporter cystinosin (CTNS) and characterized by cystine lysosomal accumulation. We show that, different from other LSDs, autophagosome number is increased, but macroautophagic flux is not impaired in cystinosis while mTOR activity is not affected. Conversely, the expression and localization of the CMA receptor LAMP2A are abnormal in CTNS-deficient cells and degradation of the CMA substrate GAPDH is defective in Ctns(-/-) mice. Importantly, cysteamine treatment, despite decreasing lysosomal overload, did not correct defective CMA in Ctns(-/-) mice or LAMP2A mislocalization in cystinotic cells, which was rescued by CTNS expression instead, suggesting that cystinosin is important for CMA activity. In conclusion, CMA impairment contributes to cell malfunction in cystinosis, highlighting the need for treatments complementary to current therapies that are based on decreasing lysosomal overload

Mitochondrial Turnover and Aging of Long-Lived Postmitotic Cells: The Mitochondrial–Lysosomal Axis Theory of Aging

It is now generally accepted that aging and eventual death of multicellular organisms is to a large extent related to macromolecular damage by mitochondrially produced reactive oxygen species, mostly affecting long-lived postmitotic cells, such as neurons and cardiac myocytes. These cells are rarely or not at all replaced during life and can be as old as the whole organism. The inherent inability of autophagy and other cellular-degradation mechanisms to remove damaged structures completely results in the progressive accumulation of garbage, including cytosolic protein aggregates, defective mitochondria, and lipofuscin, an intralysosomal indigestible material. In this review, we stress the importance of crosstalk between mitochondria and lysosomes in aging. The slow accumulation of lipofuscin within lysosomes seems to depress autophagy, resulting in reduced turnover of effective mitochondria. The latter not only are functionally deficient but also produce increased amounts of reactive oxygen species, prompting lipofuscinogenesis. Moreover, defective and enlarged mitochondria are poorly autophagocytosed and constitute a growing population of badly functioning organelles that do not fuse and exchange their contents with normal mitochondria. The progress of these changes seems to result in enhanced oxidative stress, decreased ATP production, and collapse of the cellular catabolic machinery, which eventually is incompatible with survival. Antioxid. Redox Signal. 12, 503–535