| 1. |
- Sjögren, Marie, et al.
(författare)
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Leptin deficiency reverses high metabolic state and weight loss without affecting central pathology in the R6/2 mouse model of Huntington's disease
- 2019
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961 .- 1095-953X. ; 132
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Body weight has been shown to be a predictor of clinical progression in Huntington's disease (HD). Alongside widespread neuronal pathology, both HD patients and the R6/2 mouse model of HD exhibit weight loss and increased energy expenditure, providing a rationale for targeting whole-body energy metabolism in HD. Leptin-deficient mice display low energy expenditure and increased body weight. We therefore hypothesized that normalizing energy metabolism in R6/2 mice, utilizing leptin- deficiency, would lead to a slower disease progression in the R6/2 mouse. In this study, we show that R6/2 mice on a leptin-deficient genetic background display increased body weight and increased fat mass compared to R6/2 mice, as well as wild type littermates. The increased body weight was accompanied by low energy expenditure, illustrated by a reduction in respiratory exchange rate. Leptin-deficient R6/2 mice had large white adipocytes with white adipocyte gene expression characteristics, in contrast to white adipose tissue in R6/2 mice, where white adipose tissue showed signs of browning. Leptin-deficient R6/2 mice did not exhibit improved neuropathological measures. Our results indicate that lowering energy metabolism in HD, by increasing fat mass and reducing respiratory exchange rate, is not sufficient to affect neuropathology. Further studies targeting energy metabolism in HD are warranted.
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| 2. |
- Aidemark, Mari, et al.
(författare)
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Trichoderma viride cellulase induces resistance to the antibiotic pore-forming peptide alamethicin associated with changes in the plasma membrane lipid composition of tobacco BY-2 cells
- 2010
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Ingår i: Bmc Plant Biology. - : Springer Science and Business Media LLC. - 1471-2229. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Background: Alamethicin is a membrane-active peptide isolated from the beneficial root-colonising fungus Trichoderma viride. This peptide can insert into membranes to form voltage-dependent pores. We have previously shown that alamethicin efficiently permeabilises the plasma membrane, mitochondria and plastids of cultured plant cells. In the present investigation, tobacco cells (Nicotiana tabacum L. cv Bright Yellow-2) were pre-treated with elicitors of defence responses to study whether this would affect permeabilisation. Results: Oxygen consumption experiments showed that added cellulase, already upon a limited cell wall digestion, induced a cellular resistance to alamethicin permeabilisation. This effect could not be elicited by xylanase or bacterial elicitors such as flg22 or elf18. The induction of alamethicin resistance was independent of novel protein synthesis. Also, the permeabilisation was unaffected by the membrane-depolarising agent FCCP. As judged by lipid analyses, isolated plasma membranes from cellulase-pretreated tobacco cells contained less negatively charged phospholipids ( PS and PI), yet higher ratios of membrane lipid fatty acid to sterol and to protein, as compared to control membranes. Conclusion: We suggest that altered membrane lipid composition as induced by cellulase activity may render the cells resistant to alamethicin. This induced resistance could reflect a natural process where the plant cells alter their sensitivity to membrane pore-forming agents secreted by Trichoderma spp. to attack other microorganisms, and thus adding to the beneficial effect that Trichoderma has for plant root growth. Furthermore, our data extends previous reports on artificial membranes on the importance of lipid packing and charge for alamethicin permeabilisation to in vivo conditions.
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| 3. |
- Andersson, Mats X., 1977, et al.
(författare)
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A chloroplast-localized vesicular transport system: a bio-informatics approach
- 2004
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Ingår i: BMC Genomics. - : Springer Science and Business Media LLC. - 1471-2164. ; 5:40
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Tidskriftsartikel (refereegranskat)abstract
- Background: The thylakoid membrane of higher plant chloroplasts is made of membrane lipids synthesized in the chloroplast envelope. As the inner envelope membrane and the thylakoid are separated by the aqueous stroma, a system for transporting newly synthesized lipids from the inner envelope membrane to the thylakoid is required. Ultrastructural as well as biochemical studies have indicated that lipid transport inside the chloroplast could be mediated by a system similar in characteristics to vesicular trafficking in the cytosol. If indeed the chloroplast system is related to cytosolic vesicular trafficking systems, a certain degree of sequence conservation between components of the chloroplast and the cytosolic systems could be expected. We used the Arabidopsis thaliana genome and web-based subcellular localization prediction tools to search for chloroplast-localized homologues of cytosolic vesicular trafficking components. Results: Out of the 28952 hypothetical proteins in the A. thaliana genome sequence, 1947 were predicted to be chloroplast-localized by two different subcellular localization predictors. In this chloroplast protein dataset, strong homologues for the main coat proteins of COPII coated cytosolic vesicles were found. Homologues of the small GTPases ARF1 and Sar1 were also found in the chloroplast protein dataset. Conclusion: Our database search approach gives further support to that a system similar to cytosolic vesicular trafficking is operational inside the chloroplast. However, solid biochemical data is needed to support the chloroplast localization of the identified proteins as well as their involvment in intra-chloroplast lipid trafficking.
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| 4. |
- Andersson, Mats X., 1977, et al.
(författare)
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Chloroplast biogenesis. Regulation of lipid transport to the thylakoid in chloroplasts isolated from expanding and fully expanded leaves of pea.
- 2001
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Ingår i: Plant physiology. - 0032-0889. ; 127:1, s. 184-93
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Tidskriftsartikel (refereegranskat)abstract
- To study the regulation of lipid transport from the chloroplast envelope to the thylakoid, intact chloroplasts, isolated from fully expanded or still-expanding pea (Pisum sativum) leaves, were incubated with radiolabeled lipid precursors and thylakoid membranes subsequently were isolated. Incubation with UDP[(3)H]Gal labeled monogalactosyldiacylglycerol in both envelope membranes and digalactosyldiacylglycerol in the outer chloroplast envelope. Galactolipid synthesis increased with incubation temperature. Transport to the thylakoid was slow below 12 degrees C, and exhibited a temperature dependency closely resembling that for the previously reported appearance and disappearance of vesicles in the stroma (D.J. Morré, G. Selldén, C. Sundqvist, A.S. Sandelius [1991] Plant Physiol 97: 1558-1564). In mature chloroplasts, monogalactosyldiacylglycerol transport to the thylakoid was up to three times higher than digalactosyldiacylglycerol transport, whereas the difference was markedly lower in developing chloroplasts. Incubation of chloroplasts with [(14)C]acyl-coenzyme A labeled phosphatidylcholine (PC) and free fatty acids in the inner envelope membrane and phosphatidylglycerol at the chloroplast surface. PC and phosphatidylglycerol were preferentially transported to the thylakoid. Analysis of lipid composition revealed that the thylakoid contained approximately 20% of the chloroplast PC. Our results demonstrate that lipids synthesized at the chloroplast surface as well as in the inner envelope membrane are transported to the thylakoid and that lipid sorting is involved in the process. Furthermore, the results also indicate that more than one pathway exists for galactolipid transfer from the chloroplast envelope to the thylakoid.
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| 5. |
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| 6. |
- Andersson, Mats X., 1977, et al.
(författare)
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Optical manipulation reveals strong attracting forces at membrane contact sites between endoplasmic reticulum and chloroplasts
- 2007
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Ingår i: Journal of Biological Chemistry. - 0021-9258. ; 282:2, s. 1170-1174
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryote cells depend on membrane lipid trafficking from biogenic membranes, like the endoplasmic reticulum (ER), to other membranes in the cell. Two major routes for membrane lipid transport are recognized: vesicular trafficking and lipid transfer at zones of close contact between membranes. Specific ER regions involved in such membrane contact sites (MCSs) have been isolated, and lipid transfer at MCSs as well as protein-protein interactions between the partaking membranes have been demonstrated (reviewed by Holthuis, J. C. M., and Levine, T. P. (2005) Nat. Rev. 6, 209–220). Here we present the first demonstration of the physical association between membranes involved in MCSs: by using optical imaging and manipulation, strong attracting forces between ER and chloroplasts are revealed. We used Arabidopsis thaliana expressing green fluorescent protein in the ER lumen and observed leaf protoplasts by confocal microscopy. The ER network was evident, with ER branch end points apparently localized at chloroplast surfaces. After rupture of a protoplast using a laser scalpel, the cell content was released. ER fragments remained attached to the released chloroplasts and could be stretched out by optical tweezers. The applied force, 400 pN, could not drag a chloroplast free from its attached ER, which could reflect protein-protein interactions at the ER-chloroplast MCSs. As chloroplasts rely on import of ER-synthesized lipids, we propose that lipid transfer occurs at these MCSs. We suggest that lipid transfer at the MCSs also occurs in the opposite direction, for example to channel plastid-synthesized acyl groups to supply substrates for ER-localized synthesis of membrane and storage lipids.
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| 7. |
- Andersson, Mats X., 1977, et al.
(författare)
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Phosphate-deficient oat replaces a major portion of the plasma membrane phospholipids with the galactolipid digalactosyldiacylglycerol.
- 2003
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Ingår i: FEBS letters. - 0014-5793. ; 537:1-3, s. 128-32
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Tidskriftsartikel (refereegranskat)abstract
- The plasma membranes of oat normally resemble those of other eukaryotes in containing mainly phospholipids and sterols. We here report the novel finding that the galactolipid digalactosyldiacylglycerol (DGDG) can constitute a substantial proportion of oat plasma membrane lipids, in both shoots and roots. When oat was cultivated under severe phosphate limitation, up to 70% of the plasma membrane phosphoglycerolipids were replaced by DGDG. Our finding not only reflects a far more developed potential for plasticity in plasma membrane lipid composition than often assumed, but also merits interest in the context of the limited phosphate availability in many soils.
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| 8. |
- Andersson, Mats X., 1977, et al.
(författare)
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The involvement of cytosolic lipases in converting phosphatidyl choline to substrate for galactolipid synthesis in the chloroplast envelope :
- 2004
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Ingår i: Biochimica et Biophysica Acta-Molecular and Cell Biology of Lipids. - : Elsevier BV. - 1388-1981. ; 1684:1-3, s. 46-53
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Tidskriftsartikel (refereegranskat)abstract
- Here we report that cytosolic phospholipases are involved in the utilization of phosphatidylcholine (PC) as substrate for chloroplast-localized synthesis of monogalactosyldiacylglycerol (MGDG). Isolated chloroplasts were pre-incubated with lysoPC and [C-14]18:0-CoA to form [C-14]PC. When soluble plant proteins (cytosol) and UDP-galactose were added, [C-14] MGDG was formed. An inhibitor of phospholipase D markedly lowered the formation of [C-14]MGDG, whereas thermolysin pretreatment of the chloroplasts was without effect. The cytosolic activity resided in the >100-kDa fraction. In a second approach, [C-14]PC-containing lipid mixtures were incubated with cytosol. Degradation of [C-14]PC to [C-14]diacylglycerol was highest when the lipid composition of the mixture mimicked that of the outer chloroplast envelope. We also investigated whether PC of extraplastidic origin could function as substrate for MGDG synthesis. Isolated chloroplasts were incubated with enriched endoplasmic reticulum containing radiolabelled acyl lipids. In the presence of cytosol and UDPgalactose, there was a time-dependent transfer of [C-14]PC from this fraction to chloroplasts, where [C-14]MGDG was formed. We conclude that chloroplasts recruit cytosolic phospholipase D and phosphatidic acid phosphatase to convert PC to diacylglycerol. Apparently, these lipases do not interact with chloroplast surface proteins, but rather with outer membrane lipids, either for association to the envelope or for substrate presentation. (C) 2004 Elsevier B.V. All rights reserved.
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| 9. |
- Andersson, Mats X., 1977, et al.
(författare)
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The plasma membrane and the tonoplast as major targets for phospholipid- to-glycolipid replacement and stimulation of phospholipases in the plasma membrane
- 2005
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Ingår i: Journal of Biological Chemistry. ; 280:30, s. 27578-27586
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Tidskriftsartikel (refereegranskat)abstract
- We recently reported that cultivation of oat (Avena sativa L.) without phosphate resulted in plasma membrane phosphoglycerolipids being replaced to a large extent by digalactosyldiacylglycerol (DGDG) (Andersson, M. X., Stridh, M. H., Larsson, K. E., Liljenberg, C., and Sandelius, A. S. ( 2003) FEBS Lett. 537, 128-132). We report here that DGDG is not the only non-phosphorous-containing lipid that replaces phospholipids but that also the content of glucosylceramides and sterolglycosides increased in plasma membranes as a response to phosphate starvation. In addition, phosphate deficiency induced similar changes in lipid composition in the tonoplast. The phospholipid-to-glycolipid replacement apparently did not occur to any greater extent in endoplasmic reticulum, Golgi apparatus, or mitochondrial inner membranes. In contrast to the marked effects on lipid composition, the polypeptide patterns were largely similar between root plasma membranes from well-fertilized and phosphate-limited oat, although the latter condition induced at least four polypeptides, including a chaperone of the HSP80 or HSP90 family, a phosphate transporter, and a bacterial-type phosphoesterase. The latter polypeptide reacted with an antibody raised against a phosphate deficiency-induced phospholipase C from Arabidopsis thaliana (Nakamura, Y., Awai, K., Masuda, T., Yoshioka, Y., Takamiya, K., and Ohta, H. ( 2005) J. Biol. Chem. 280, 7469-7476). In plasma membranes from oat, however, a phospholipase D-type activity and a phosphatidic acid phosphatase were the dominant lipase activities induced by phosphate deficiency. Our results reflect a highly developed plasticity in the lipid composition of the plasma membrane and the tonoplast. In addition, phosphate deficiency-induced alterations in plasma membrane lipid composition may involve different sets of lipid-metabolizing enzymes in different plant tissues or species, at different stages of plant development and/or at different stages of stress adjustments.
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| 10. |
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