| 1. |
- Gustafsson, Gabriel, et al.
(author)
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Secretion and uptake of α-synuclein via extracellular vesicles in cultured cells
- 2018
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In: Cellular and molecular neurobiology. - : Springer Science and Business Media LLC. - 0272-4340 .- 1573-6830. ; 38:8, s. 1539-1550
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Journal article (peer-reviewed)abstract
- In Parkinson’s disease and other Lewy body disorders, the propagation of pathology has been accredited to the spreading of extracellular α-synuclein (α-syn). Although the pathogenic mechanisms are not fully understood, cell-to-cell transfer of α-syn via exosomes and other extracellular vesicles (EVs) has been reported. Here, we investigated whether altered molecular properties of α-syn can influence the distribution and secretion of α-syn in human neuroblastoma cells. Different α-syn variants, including α-syn:hemi-Venus and disease-causing mutants, were overexpressed and EVs were isolated from the conditioned medium. Of the secreted α-syn, 0.1–2% was associated with vesicles. The major part of EV α-syn was attached to the outer membrane of vesicles, whereas a smaller fraction was found in their lumen. For α-syn expressed with N-terminal hemi-Venus, the relative levels associated with EVs were higher than for WT α-syn. Moreover, such EV-associated α-syn:hemi-Venus species were internalized in recipient cells to a higher degree than the corresponding free-floating forms. Among the disease-causing mutants, A53T α-syn displayed an increased association with EVs. Taken together, our data suggest that α-syn species with presumably lost physiological functions or altered aggregation properties may shift the cellular processing towards vesicular secretion. Our findings thus lend further support to the tenet that EVs can mediate spreading of harmful α-syn species and thereby contribute to the pathology in α-synucleinopathies.
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| 2. |
- Kristiansen, Per Eugen, et al.
(author)
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Nuclear Magnetic Resonance Structure and Mutational Analysis of the Lactococcin A Immunity Protein.
- 2016
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In: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 55:45, s. 6250-6257
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Journal article (peer-reviewed)abstract
- The class IId bacteriocin lactococcin A and the pediocin-like bacteriocins induce membrane leakage and cell death by specifically binding the mannose phophotransferase system (man-PTS) on their target cells. The bacteriocins' cognate immunity proteins that protect the producer cell from its own bacteriocin recognize and bind to the bacteriocin-man-PTS complex and thereby block membrane leakage. In this study, we have determined the three-dimensional structure of the lactococcin A immunity protein (LciA) by the use of nuclear magnetic resonance spectroscopy. LciA forms a four-helix bundle structure with a flexible C-terminal tail. Despite the low degree of sequence similarity between LciA and the pediocin-like immunity proteins, they share the same fold. However, there are certain differences between the structures. The C-terminal helix in LciA is considerably shorter than that observed in the pediocin-like immunity proteins, and the surface potentials of the immunity proteins differ. Truncated variants of LciA in which 6 or 10 of the C-terminal residues were removed yielded a reduced degree of protection, indicating that the unstructured C-terminal tail is important for the functionality of the immunity proteins.
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| 3. |
- Persson, Camilla, 1976
(author)
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Predicting the Long-Term Insulation Performance of District Heating Pipes
- 2015
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Doctoral thesis (other academic/artistic)abstract
- The aim of the studies that comprise this thesis was to predict the heat loss over timefrom a range of district heating pipes insulated with closed-cells foam. The thermalconductivity of the foam changes over time when it is not diffusion-tight encapsulatedagainst the environment, as diffusion alters the cell gas composition until it reachesequilibrium with the surrounding air. Over the first thirty years of use the insulationcapacity of a straight pipe of medium size insulated with polyurethane foam decreasesby about 10%. The insulating gases cyclopentane and carbon dioxide initially presentin the foam cells diffuse out of the foam over time, while nitrogen and oxygen fromthe air diffuse into it. Complete ageing increases the thermal conductivity of theinsulation by about 10 mW·m-1·K-1, but it is a slow process that takes several years.Equilibrium is not even reached after 100 years. In this work models have beenderived that can be used to predict the long-term heat flow from the pipes andinvestigate the influence of factors that have an impact.Finite difference models for the pipes alone are presented, which consider thevariation of the cell gas composition over the foam cross section. All gases areconsidered in the gas phase. But cyclopentane is also considered in dissolved state, aswell as potentially in liquid state depending on the amount and the temperaturepresent. In order to determine the solubility of cyclopentane in the polyurethanematrix of the foam measurements were performed. The solubility was found todecrease with temperature. About 50% of the cyclopentane was dissolved at roomtemperature, while only about 35% was dissolved at 50ᵒC. There is a weak couplingbetween the heat conduction (i.e. temperature) and the gas diffusion (i.e. cell gascontent) due to the fact that the thermal conductivity is dependent both on thetemperature and the cell gas content, which has been taken into consideration. Bothsingle and twin pipe geometry have been studied. Complex mathematics in the formof a coordinate transformation is needed to perform the predictions for twin pipegeometry.To model installed pipes, a stationary model for annularly insulated pipes in theground has been developed, which also involves complicated mathematics. Thetemperature is represented by series expansions; in each region with differing thermalconductivity a separate expansion is used. The expansions are matched to each otherat the region boundaries and chosen to fulfil the boundary conditions.Finally, the measured cell gas status of aged pipes and the results obtained bymodelling based on assumptions of their initial status and ageing conditions have beencompared. It was found that the actual aged pipes contained less oxygen and morecarbon dioxide than predicted. This is probably due to oxidation. It is interesting tonote that not only the oxygen but also the carbon dioxide content is influenced byoxidation. By consuming oxygen and producing carbon dioxide the oxidation willslow down the decrease of the insulation performance.
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