Small heat-shock proteins interact with a flanking domain to suppress polyglutamine aggregation

Small heat-shock proteins (sHsps) are molecular chaperones that play an important protective role against cellular protein misfolding by interacting with partially unfolded proteins on their off-folding pathway, preventing their aggregation. Polyglutamine (polyQ) repeat expansion leads to the formation of fibrillar protein aggregates and neuronal cell death in nine diseases, including Huntington disease and the spinocerebellar ataxias (SCAs). There is evidence that sHsps have a role in suppression of polyQ-induced neurodegeneration; for example, the sHsp alphaB-crystallin (αB-c) has been identified as a suppressor of SCA3 toxicity in a Drosophila model. However, the molecular mechanism for this suppression is unknown. In this study we tested the ability of αB-c to suppress the aggregation of a polyQ protein. We found that αB-c does not inhibit the formation of SDS-insoluble polyQ fibrils. We further tested the effect of αB-c on the aggregation of ataxin-3, a polyQ protein that aggregates via a two-stage aggregation mechanism. The first stage involves association of the N-terminal Josephin domain followed by polyQ-mediated interactions and the formation of SDS-resistant mature fibrils. Our data show that αB-c potently inhibits the first stage of ataxin-3 aggregation; however, the second polyQ-dependent stage can still proceed. By using NMR spectroscopy, we have determined that αB-c interacts with an extensive region on the surface of the Josephin domain. These data provide an example of a domain/region flanking an amyloidogenic sequence that has a critical role in modulating aggregation of a polypeptide and plays a role in the interaction with molecular chaperones to prevent this aggregation

PFD: a database for the investigation of protein folding kinetics and stability

We have developed a new database that collects all protein folding data into a single, easily accessible public resource. The Protein Folding Database (PFD) contains annotated structural, methodological, kinetic and thermodynamic data for more than 50 proteins, from 39 families. A user-friendly web interface has been developed that allows powerful searching, browsing and information retrieval, whilst providing links to other protein databases. The database structure allows visualization of folding data in a useful and novel way, with a long-term aim of facilitating data mining and bioinformatics approaches. PFD can be accessed freely at http://pfd.med.monash.edu.au

Calorie Restriction Attenuates Terminal Differentiation of Immune Cells

Immune senescence is a natural consequence of aging and may contribute to frailty and loss of homeostasis in later life. Calorie restriction increases healthy life-span in C57BL/6J (but not DBA/2J) mice, but whether this is related to preservation of immune function, and how it interacts with aging, is unclear. We compared phenotypic and functional characteristics of natural killer (NK) cells and T cells, across the lifespan, of calorie-restricted (CR) and control C57BL/6 and DBA/2 mice. Calorie restriction preserves a naïve T cell phenotype and an immature NK cell phenotype as mice age. The splenic T cell populations of CR mice had higher proportions of CD11a-CD44locells, lower expression of TRAIL, KLRG1, and CXCR3, and higher expression of CD127, compared to control mice. Similarly, splenic NK cells from CR mice had higher proportions of less differentiated CD11b-CD27+cells and correspondingly lower proportions of highly differentiated CD11b+CD27-NK cells. Within each of these subsets, cells from CR mice had higher expression of CD127, CD25, TRAIL, NKG2A/C/E, and CXCR3 and lower expression of KLRG1 and Ly49 receptors compared to controls. The effects of calorie restriction on lymphoid cell populations in lung, liver, and lymph nodes were identical to those seen in the spleen, indicating that this is a system-wide effect. The impact of calorie restriction on NK cell and T cell maturation is much more profound than the effect of aging and, indeed, calorie restriction attenuates these age-associated changes. Importantly, the effects of calorie restriction on lymphocyte maturation were more marked in C57BL/6 than in DBA/2J mice indicating that delayed lymphocyte maturation correlates with extended lifespan. These findings have implications for understanding the interaction between nutritional status, immunity, and healthy lifespan in aging populations

PolyQ: a database describing the sequence and domain context of polyglutamine repeats in proteins

The polyglutamine diseases are caused in part by a gain-of-function mechanism of neuronal toxicity involving protein conformational changes that result in the formation and deposition of β-sheet rich aggregates. Recent evidence suggests that the misfolding mechanism is context-dependent, and that properties of the host protein, including the domain architecture and location of the repeat tract, can modulate aggregation. In order to allow the bioinformatic investigation of the context of polyglutamines, we have constructed a database, PolyQ (http://pxgrid.med.monash.edu.au/polyq). We have collected the sequences of all human proteins containing runs of seven or more glutamine residues and annotated their sequences with domain information. PolyQ can be interrogated such that the sequence context of polyglutamine repeats in disease and non-disease associated proteins can be investigated

Formation and stability of self-assembled coherent islands in highly mismatched heteroepitaxy

We study the energetics of island formation in Stranski-Krastanow growth within a parameter-free approach. It is shown that an optimum island size exists for a given coverage and island density if changes in the wetting layer morphology after the 3D transition are properly taken into account. Our approach reproduces well the experimental island size dependence on coverage, and indicates that the critical layer thickness depends on growth conditions. The present study provides a new explanation for the (frequently found) rather narrow size distribution of self-assembled coherent islands.Comment: 4 pages, 5 figures, In print, Phys. Rev. Lett. Other related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Cryptococcal Meningitis Screening and Community-based Early Adherence Support in People With Advanced Human Immunodeficiency Virus Infection Starting Antiretroviral Therapy in Tanzania and Zambia: A Cost-effectiveness Analysis

BACKGROUND: A randomized trial demonstrated that among people living with late-stage human immunodeficiency virus (HIV) infection initiating antiretroviral therapy, screening serum for cryptococcal antigen (CrAg) combined with adherence support reduced all-cause mortality by 28%, compared with standard clinic-based care. Here, we present the cost-effectiveness. METHODS: HIV-infected adults with CD4 count <200 cells/μL were randomized to either CrAg screening plus 4 weekly home visits to provide adherence support or to standard clinic-based care in Dar es Salaam and Lusaka. The primary economic outcome was health service care cost per life-year saved as the incremental cost-effectiveness ratio (ICER), based on 2017 US dollars. We used nonparametric bootstrapping to assess uncertainties and univariate deterministic sensitivity analysis to examine the impact of individual parameters on the ICER. RESULTS: Among the intervention and standard arms, 1001 and 998 participants, respectively, were enrolled. The annual mean cost per participant in the intervention arm was US$339 (95$331-$347), resulting in an incremental cost of the intervention of US$77 (95% CI, $66-$88). The incremental cost was similar when analysis was restricted to persons with CD4 count <100 cells/μL. The ICER for the intervention vs standard care, per life-year saved, was US$70 (95$43-$211) for all participants with CD4 count up to 200 cells/μL and US$91 (95% CI, $49-$443) among those with CD4 counts <100 cells /μL. Cost-effectveness was most sensitive to mortality estimates. CONCLUSIONS: Screening for cryptococcal antigen combined with a short period of adherence support, is cost-effective in resource-limited settings