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| 2. |
- Brännström, Kristoffer, et al.
(författare)
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The N-terminal Region of Amyloid β Controls the Aggregation Rate and Fibril Stability at Low pH Through a Gain of Function Mechanism
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:31, s. 10956-10964
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease is linked to a pathological polymerization of the endogenous amyloid β-peptide (Aβ) that ultimately forms amyloid plaques within the human brain. We used surface plasmon resonance (SPR) to measure the kinetic properties of Aβ fibril formation under different conditions during the polymerization process. For all polymerization processes, a critical concentration of free monomers, as defined by the dissociation equilibrium constant (KD), is required for the buildup of the polymer, for example, amyloid fibrils. At concentrations below the KD, polymerization cannot occur. However, the KD for Aβ has previously been shown to be several orders of magnitude higher than the concentrations found in the cerebrospinal and interstitial fluids of the human brain, and the mechanism by which Aβ amyloid forms in vivo has been a matter of debate. Using SPR, we found that the KD of Aβ dramatically decreases as a result of lowering the pH. Importantly, this effect enables Aβ to polymerize within a picomolar concentration range that is close to the physiological Aβ concentration within the human brain. The stabilizing effect is dynamic, fully reversible, and notably pronounced within the pH range found within the endosomal and lysosomal pathways. Through sequential truncation, we show that the N-terminal region of Aβ contributes to the enhanced fibrillar stability due to a gain of function mechanism at low pH. Our results present a possible route for amyloid formation at very low Aβ concentrations and raise the question of whether amyloid formation in vivo is restricted to a low pH environment. These results have general implications for the development of therapeutic interventions.
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| 4. |
- Chamcheu, Jean Christopher, et al.
(författare)
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Chemical Chaperones Protect Epidermolysis Bullosa Simplex Keratinocytes from Heat Stress-Induced Keratin Aggregation : Involvement of Heat Shock Proteins and MAP Kinases
- 2011
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Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 0022-202X .- 1523-1747. ; 131:8, s. 1684-1691
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Tidskriftsartikel (refereegranskat)abstract
- Epidermolysis bullosa simplex (EBS) is a blistering skin disease caused by mutations in keratin genes (KRT5 or KRT14), with no existing therapies. Aggregates of misfolded mutant keratins are seen in cultured keratinocytes from severe EBS patients. In other protein-folding disorders, involvement of molecular chaperones and the ubiquitin-proteasome system may modify disease severity. In this study, the effects of heat stress on keratin aggregation in immortalized cells from two patients with EBS (KRT5) and a healthy control were examined with and without addition of various test compounds. Heat-induced (43 °C, 30 minutes) aggregates were observed in all cell lines, the amount of which correlated with the donor phenotype. In EBS cells pre-exposed to proteasome inhibitor, MG132, and p38-mitogen-activated protein kinase (MAPK) inhibitor, SB203580, the proportion of aggregate-positive cells increased, suggesting a role of proteasomes and phosphorylation in removing mutated keratin. In contrast, aggregates were reduced by pretreatment with two chemical chaperones, trimethylamine N-oxide (TMAO) and 4-phenylbutyrate (4-PBA). TMAO also modulated stress-induced p38/c-jun N-terminal kinase (JNK) activation and expression of heat shock protein (HSPA1A), the latter of which colocalized with phosphorylated keratin 5 in EBS cells. Taken together, our findings suggest therapeutic targets for EBS and other keratinopathies.
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| 5. |
- Chamcheu, Jean Christopher, et al.
(författare)
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Chemical chaperones protect epidermolysis bullosa simplex keratinocytes from heat stress-induced keratin aggregation: : Involvement of heat shock proteins and MAP kinases
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Ingår i: Journal of Investigative Dermatology. - 0022-202X .- 1523-1747.
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Tidskriftsartikel (refereegranskat)abstract
- Epidermolysis bullosa simplex (EBS) is an inherited epithelial tissue fragility disorder due to mutations in keratin genes (KRT5 or KRT14), with no existing therapies. Aggregates of misfolded mutant keratins are seen in cultured keratinocytes from severe EBS patients. In some protein folding disorders such as cystic fibrosis and Alzheimer’s disease, chaperones and the ubiquitin-proteasome system modify disease severity, suggesting a novel therapeutic approach even for EBS. In this study, the effects of two chemical chaperones (trimethylamine-N oxide (TMAO) and 4-phenylbutyrate (4-PBA)) on heat stress-induced keratin aggregation responses were examined in newly and previously established immortalized control and EBS patient-derived keratinocyte cell lines. Heat-induced keratin-positive aggregates were observed in all EBS cells, which were most prominent in severe keratin-defective cell lines and less so in normal cells. The proportion of cells containing aggregates were dramatically reduced by TMAO and 4-PBA pretreatment. Furthermore, heat stress greatly induced MAP kinase activation (p38 and JNK) and increased Hsp70/Hsc70 expression, and TMAO was able to transiently modulate these effects. The results suggest that TMAO rescue may involve components of the endogenous chaperone and MAPK machineries, which may represent novel targets for the development of more effective treatments for EBS and other keratin-related genetic disorders.
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| 6. |
- Chamcheu, Jean Christopher, et al.
(författare)
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Immortalized keratinocytes derived from patients with epidermolytic ichthyosis reproduce the disease phenotype : A useful in vitro model for testing new treatments
- 2011
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Ingår i: British Journal of Dermatology. - : British Association of Dermatologists. - 0007-0963 .- 1365-2133. ; 164:2, s. 263-272
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Tidskriftsartikel (refereegranskat)abstract
- Background: Epidermolytic ichthyosis (EI) is a skin fragility disorder caused by mutations in genes encoding suprabasal keratins 1 and 10. While the aetiology of EI is known, model systems are needed for pathophysiological studies and development of novel therapies. Objectives To generate immortalized keratinocyte lines from patients with EI for studies of EI cell pathology and the effects of chemical chaperones as putative therapies. Methods We derived keratinocytes from three patients with EI and one healthy control and established immortalized keratinocytes using human papillomavirus 16-E6/E7. Growth and differentiation characteristics, ability to regenerate organotypic epidermis, keratin expression, formation of cytoskeletal aggregates, and responses to heat shock and chemical chaperones were assessed. Results The cell lines EH11 (K1-p.Val176-Lys197del), EH21 (K10-p.156Arg>Gly), EH31 (K10-p.Leu161-Asp162del) and NKc21 (wild-type) currently exceed 160 population doublings and differentiate when exposed to calcium. At resting state, keratin aggregates were detected in 9% of calcium-differentiated EH31 cells, but not in any other cell line. Heat stress further increased this proportion to 30% and also induced aggregates in 3% of EH11 cultures. Treatment with trimethylamine N-oxide and 4-phenylbutyrate (4-PBA) reduced the fraction of aggregate-containing cells and affected the mRNA expression of keratins 1 and 10 while 4-PBA also modified heat shock protein 70 (HSP70) expression. Furthermore, in situ proximity ligation assay suggested a colocalization between HSP70 and keratins 1 and 10. Reconstituted epidermis from EI cells cornified but EH21 and EH31 cells produced suprabasal cytolysis, closely resembling the in vivo phenotype. Conclusions These immortalized cell lines represent a useful model for studying EI biology and novel therapies.
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| 7. |
- Gron, Kurt J., et al.
(författare)
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Archaeological cereals as an isotope record of long-term soil health and anthropogenic amendment in southern Scandinavia
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 253
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining soil health is integral to agricultural production, and the archaeological record contains multiple lines of palaeoclimatic and palaeoenvironmental proxy evidence that can contribute to the understanding and analysis of long-term trajectories of change that are key for contextualizing 21st century global environmental challenges. Soil is a capital resource and its nutrient balance is modified by agricultural activities, making it necessary to ensure soil productivity is maintained and managed through human choices and actions. Since prehistory this has always been the case; soil is a non-renewable resource within a human lifetime. Here, we present and interpret carbon and nitrogen isotope analysis of charred cereals from southern Scandinavia. Anthropogenic effects on soils are evident from the initiation of farming 6000 years ago, as is amendment to counteract its effects. The earliest cereals were planted on pristine soils, and by the late Neolithic, agriculture extensified. By the Iron Age it was necessary to significantly amend depleted soils to maintain crop yields. We propose that these data provide a record of soil water retention, net precipitation and amendment. From the start of the Neolithic there is a concurrent decrease in both Δ13C and δ15N, mitigated only by the replacement of soil organic content in the form of manure in the Iron Age. The cereal isotopes provide a record of trajectories of agricultural sustainability and anthropogenic adaptation for nearly the entire history of farming in the region.
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| 8. |
- Martinsson, Jesper, 1981-
(författare)
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Ecology of juvenile turbot and flounder in the Central Baltic Sea : Implications for recruitment
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our understanding of turbot and flounder ecology in the Baltic Sea is insufficient for sound management decisions. This thesis aims to fill some gaps in current knowledge by providing information of the ecology of turbot and flounder within their juvenile habitat, and to relate these findings to issues assumed relevant for recruitment variation. Main focus is on turbot due to its relatively low abundance and high variability in recruitment. The distribution of both species was studied on different scales, as was environmental effects on food consumption in 0-group turbot. The 0-group turbot display a relatively restricted spatial distribution compared to flounder. This is possibly due to a more specialized diet, which may make them more vulnerable to habitat degradation, especially eutrophication as a strong negative correlation was found with the organic content in the sediment. The species show high temporal and spatial overlap when settling in July-September, with peak abundances in August, and at depths <1 m. Both species display sedentary behavior within the nursery ground. Compared to flounder, turbot was more mobile potentially due to its restricted diet calling for extended searches. For turbot, feeding conditions appear to vary between size groups, which potentially could cause variations in survival between years through size-selective mortality. But, the predation may be low in central Baltic Sea as the abundance of the main predator, brown shrimp are comparatively low during flatfish occupancy. A significant positive relationship was found between the recruitment of turbot and flounder, which suggests that no inter-specific interactions during the juvenile stage affect recruitment. This co-variation also suggests that the recruitment of the species is determined by the same phenomena, potentially by large scale abiotic factors during the egg- and larval stage. For turbot, additional variability is potentially generated during the juvenile stage due to its relatively restricted food and habitat requirements. The specific habitat demands of turbot revealed in this thesis may be used to protect and restore essentially nursery grounds.
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| 9. |
- Mojtaba Ghiasi, Seyed, et al.
(författare)
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The Endoplasmic Reticulum Chaperone Glucose-Regulated Protein 94 is Essential for Proinsulin Handling
- 2019
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 68:4, s. 747-760
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Tidskriftsartikel (refereegranskat)abstract
- Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is under-investigated. Here, we have explored the importance of glucose regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 co-immunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life and lowered intracellular proinsulin and insulin levels. This phenotype was accompanied by post-ER proinsulin misprocessing and higher numbers of enlarged insulin granules that contained amorphic material with reduced immunogold staining for mature insulin. Insulin granule exocytosis was two-fold accelerated but the secreted insulin had diminished bioactivity. Moreover, GRP94 knockdown or knockout in β-cells selectively activated Protein Kinase R-like Endoplasmic Reticulum Kinase (PERK), without increasing apoptosis levels. Finally, GRP94 mRNA was overexpressed in islets from T2D patients. We conclude that GRP94 is a chaperone crucial for proinsulin handling and insulin secretion.
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| 10. |
- Mortensen, Morten Fischer, et al.
(författare)
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Turfs and Timbers- Resource use in the construction of the Viking Age Ring Fortress Borgring, Southeast Denmark
- 2021
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Ingår i: Danish Journal of Archaeology. - : Det Kgl. Bibliotek/Royal Danish Library. - 2166-2290 .- 2166-2282. ; 10, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Viking Age ring fortresses were some of the largest construction projects in Danish prehistory. In this article we reconstruct the amount of turf and timber used in the construction of the Borgring ring fortress and estimate the resource area needed to supply the building materials. Using REVEALS pollen data modelling, we quantify the regional oak land cover and estimate the resource area. The results show that even though Borgring was built in an open cultural landscape, sufficient supply of oak for the construction would have been accessible within a few kilometres from the fortress.
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