| 1. |
- Stefansdottir, Halla Steinunn
(creator_code:cre_t)
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Performance of An Urban Archive as an English Garden at SPOR festival
- 2019
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Premiere of An Urban Archive as an English Garden by Davíð Brynjar Franzson at the SPOR festival, Aarhus, Denmark. The work includes field recordings by Halla Steinunn Stefánsdóttir. The festival and choice of location was curated by Anna Berit Asp Christensen and Anne Marqvardsen.
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| 2. |
- Eriksson, Irene, et al.
(författare)
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The Early Awareness and Alert System in Sweden : History and Current Status
- 2017
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Ingår i: Frontiers in Pharmacology. - : Frontiers Media S.A.. - 1663-9812. ; 8
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Forskningsöversikt (refereegranskat)abstract
- The Swedish EAA System started as a regional initiative and rapidly grew to become a national level activity. An important feature of the system today is its complete integration into the national process for managed introduction and follow-up of new medicines. The system will continue to evolve as a response both to the changing landscape of health innovations and to new policy initiatives at the regional, national and international level.
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| 3. |
- Christensen, Anna, et al.
(författare)
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Higher plant calreticulins have acquired specialized functions in arabidopsis
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:6, s. e11342-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Calreticulin (CRT) is a ubiquitous ER protein involved in multiple cellular processes in animals, such as protein folding and calcium homeostasis. Like in animals, plants have evolved divergent CRTs, but their physiological functions are less understood. Arabidopsis contains three CRT proteins, where the two CRTs AtCRT1a and CRT1b represent one subgroup, and AtCRT3 a divergent member. Methodology/Principal Findings: Through expression of single Arabidopsis family members in CRT-deficient mouse fibroblasts we show that both subgroups have retained basic CRT functions, including ER Ca2+-holding potential and putative chaperone capabilities. However, other more general cellular defects due to the absence of CRT in the fibroblasts, such as cell adhesion deficiencies, were not fully restored. Furthermore, in planta expression, protein localization and mutant analyses revealed that the three Arabidopsis CRTs have acquired specialized functions. The AtCRT1a and CRT1b family members appear to be components of a general ER chaperone network. In contrast, and as recently shown, AtCRT3 is associated with immune responses, and is essential for responsiveness to the bacterial Pathogen-Associated Molecular Pattern (PAMP) elf18, derived from elongation factor (EF)-Tu. Whereas constitutively expressed AtCRT1a fully complemented Atcrt1b mutants, AtCRT3 did not. Conclusions/Significance: We conclude that the physiological functions of the two CRT subgroups in Arabidopsis have diverged, resulting in a role for AtCRT3 in PAMP associated responses, and possibly more general chaperone functions for AtCRT1a and CRT1b.
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| 4. |
- Christensen, Anna, et al.
(författare)
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Functional characterization of Arabidopsis calreticulin1a : a key alleviator of endoplasmic reticulum stress
- 2008
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Ingår i: Plant and Cell Physiology. - : Oxford University Press. - 0032-0781 .- 1471-9053. ; 49:6, s. 912-924
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Tidskriftsartikel (refereegranskat)abstract
- The chaperone calreticulin plays important roles in a variety of processes in the endoplasmic reticulum (ER) of animal cells, such as Ca2+ signaling and protein folding. Although the functions of calreticulin are well characterized in animals, only indirect evidence is available for plants. To increase our understanding of plant calreticulins we introduced one of the Arabidopsis isoforms, AtCRT1a, into calreticulin-deficient (crt–/–) mouse embryonic fibroblasts. As a result of calreticulin deficiency, the mouse crt–/– fibroblasts have decreased levels of Ca2+ in the ER and impaired protein folding abilities. Expression of the AtCRT1a in mouse crt–/– fibroblasts rescued these phenotypes, i.e. AtCRT1a restored the Ca2+-holding capacity and chaperone functions in the ER of the mouse crt–/– fibroblasts, demonstrating that the animal sorting machinery was also functional for a plant protein, and that basic calreticulin functions are conserved across the Kingdoms. Expression analyses using a β-glucuronidase (GUS)–AtCRT1a promoter construct revealed high expression of CRT1a in root tips, floral tissues and in association with vascular bundles. To assess the impact of AtCRT1a in planta, we generated Atcrt1a mutant plants. The Atcrt1a mutants exhibited increased sensitivity to the drug tunicamycin, an inducer of the unfolded protein response. We therefore conclude that AtCRT1a is an alleviator of the tunicamycin-induced unfolded protein response, and propose that the use of the mouse crt–/– fibroblasts as a calreticulin expression system may prove useful to assess functionalities of calreticulins from different species.
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| 5. |
- Christensen, Anna
(författare)
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Plant Calreticulins -Calcium-binding proteins with many functions
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Endoplasmic reticulum (ER) plays an important role in protein synthesis, folding, maturation and transport of newly synthesized proteins, as well as the regulation of cellular Ca2+ homeostasis. A protein that is involved in several of these functions in the ER is calreticulin (CRT), which is a Ca2+-binding chaperone that resides in the lumen of the ER. Animal CRT is a multifunctional protein involved in numerous cellular functions, such as protein folding, Ca2+ binding, regulation of gene expression, apoptosis and cell adhesion. Much less is known about CRTs in plants. Three Arabidopsis CRT isoforms have been identified and can be divided into two distinct CRT groups; CRT1a/1b and CRT3. To increase the understanding of plant CRTs, functional characteristics and expression profiles were examined. The regulation of cellular Ca2+ homeostasis was investigated using tobacco (Nicotiana tabacum) suspension cell lines with altered levels of maize CRT. An increased production of CRT in tobacco cell lines enabled growth in high calcium medium. Expression studies of Arabidopsis CRTs showed an overlapping expression and localization of CRT1a and 1b in floral tissues, leaves, elongating root cells, expanding cotyledons and root cap, while CRT3 was mainly expressed in cauline and wilting leaves, expanding cotyledons, elongating root cells and with no expression in pollen and root cap. For functional studies of plant CRTs, AtCRT1a and AtCRT3, respectively, were introduced into CRT-deficient (crt-/-) mouse embryonic fibroblasts. As a result of CRT-deficiency the mouse crt-/- fibroblasts have decreased levels of Ca2+ in the endoplasmic reticulum and impaired protein folding abilities. Both plant isoforms rescued these phenotypes, that is they were able to restore Ca2+-holding capacity and chaperone functions in the ER of the mouse crt-/- fibroblasts. This demonstrates that the animal sorting machinery was functional also with the plant CRTs, and that basic CRT functions are conserved across the Kingdoms. To understand the role of CRT in planta, T-DNA insertion mutants were collected for all three genes. Atcrt1a exhibited a conditional phenotype under tunicamycin stress, while disruption of AtCRT1b caused a constitutive ER stress. The double mutant Atcrt1a crt1b showed retarded growth in both normally-grown and etiolated seedlings as well as lower seed production. The Atcrt3 mutant was less sensitive to tunicamycin and CRT3 cDNA did not complement the Atcrt1b mutant, while CRT1a cDNA rescued the Atcrt1b mutant. These studies show that AtCRT1a and AtCRT1b can compensate for each other, although similar expression patterns was observed between CRT1a and 1b, cell-specific localization differences was also observed with specific antibodies. The differences observed between the CRT1 and CRT3 isoform groups suggest different physiological roles for AtCRT3 compared to AtCRT1a and 1b.
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| 6. |
- Christensen, Anna, et al.
(författare)
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Overexpression of the Ca2+-binding protein calreticulin in the endoplasmic reticulum improves growth of tobacco cell suspensions (Nicotiana tabacum) in high-Ca2+ medium
- 2005
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 123:1, s. 92-99
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Tidskriftsartikel (refereegranskat)abstract
- Calreticulin (CRT) is a eukaryotic, highly conserved, Ca2+-binding protein predominantly located in the endoplasmic reticulum (ER) lumen. In addition to being involved in the regulation of cellular Ca2+, calreticulin is a key quality control element during protein folding in the ER lumen. Tobacco (Nicotiana tabacum L.) suspension cells overexpressing a maize CRT (CRT1a) were used here to examine the properties of CRT in growing plant cells with respect to stress exposure. The endogenous CRT gene was induced rapidly after subculturing of the cells to new medium. In accordance, the CRT protein levels increased, peaking at days 3-4. At day 5, when the CRT transcript levels had levelled off, a further increase in endogenous CRT expression was obtained when the cells were treated with excess Ca2+ or the N-linked glycosylation inhibitor tunicamycin. Whereas the response to Ca2+ occurred within 30 min, the induction by tunicamycin took several hours to be established. Transforming tobacco cells with maize CRT1a, under a constitutive mannopine synthase promoter, resulted in a stable level of expressed CRT1a during the growth cycle compared with endogenous CRT. The CRTs showed differences in attached glycans, but both contained the high mannose-rich-type glycans characteristic of ER proteins. In agreement with an ER location, both tobacco CRT and the transgene product CRT1a codistributed with the ER marker NADH cytochrome c reductase after density gradient centrifugation of microsomal fractions from tobacco cells. Increased production of CRT, as was obtained in the transgenic tobacco cell lines, made cells more tolerant than wild-type cells to high Ca2+ during growth. These data suggest that overexpression of CRT1a in plant cells results in a more efficient calcium buffering capacity in the ER.
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