| 1. |
- Ahnström, Josefin, et al.
(author)
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Activated protein C cofactor function of protein S: a novel role for a gamma-carboxyglutamic acid residue
- 2011
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 117:24, s. 6685-6693
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Journal article (peer-reviewed)abstract
- Protein S has an important anticoagulant function by acting as a cofactor for activated protein C (APC). We recently reported that the EGF1 domain residue Asp95 is critical for APC cofactor function. In the present study, we examined whether additional interaction sites within the Gla domain of protein S might contribute to its APC cofactor function. We examined 4 residues, composing the previously reported "Face1" (N33S/P35T/E36A/Y39V) variant, as single point substitutions. Of these protein S variants, protein S E36A was found to be almost completely inactive using calibrated automated thrombography. In factor Va inactivation assays, protein S E36A had 89% reduced cofactor activity compared with wild-type protein S and was almost completely inactive in factor VIIIa inactivation; phospholipid binding was, however, normal. Glu36 lies outside the omega-loop that mediates Ca2+-dependent phospholipid binding. Using mass spectrometry, it was nevertheless confirmed that Glu36 is gamma-carboxylated. Our finding that Gla36 is important for APC cofactor function, but not for phospholipid binding, defines a novel function (other than Ca2+ coordination/phospholipid binding) for a Gla residue in vitamin K-dependent proteins. It also suggests that residues within the Gla and EGF1 domains of protein S act cooperatively for its APC cofactor function. (Blood. 2011;117(24):6685-6693)
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| 2. |
- Ahnström, Josefin, et al.
(author)
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HDL Stimulates apoM Secretion.
- 2010
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In: Protein & Peptide Letters. - 0929-8665. ; Jul 1, s. 1285-1289
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Journal article (peer-reviewed)abstract
- Apolipoprotein M (apoM) in human plasma is mainly associated with HDL. A retained signal peptide anchors apoM to the lipoproteins. To investigate the role of the signal peptide in the transfer of apoM from the synthesizing cell to the lipoproteins, wildtype apoM cDNA and the Q(22)A mutant, introducing a signal peptidase cleavage site, were used to stably transfect HEK293 cells, which intrinsically do not express apolipoproteins. When cultured under serum-free conditions, wildtype apoM was, in contrast to Q(22)A, poorly secreted. Addition of serum or purified HDL stimulated secretion of wildtype apoM, which was recovered in the medium incorporated in HDL. The liver cell line HepG2, which synthesizes HDL, was cultured under serum-free conditions and found to secrete apoM as part of an HDL-like particle. In conclusion, due to its retained signal peptide, apoM is poorly secreted unless HDL is either coexpressed or added to the culture medium.
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| 3. |
- Ahnström, Josefin, et al.
(author)
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Plasma concentrations of apolipoproteins A-I, B, and M in patients with abdominal aortic aneurysms.
- 2010
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In: Clinical Biochemistry. - : Elsevier BV. - 1873-2933 .- 0009-9120. ; 43:4-5, s. 407-410
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Journal article (peer-reviewed)abstract
- Objectives: Apolipoproteins play important roles in the development of atherosclerosis but their involvement in the pathogenesis of abdominal aortic aneurysm (AAA) is poorly understood. The aim was to investigate whether apoA-I, apoB and apoM are independently associated with AAA. Design and methods: Plasma apoA-I, apoB and apoM were measured in 343 patients with AAA and in 214 elderly apparently healthy control individuals from the background population. Results: AAA patients had lower apolipoprotein levels, as compared to healthy individuals; apoA-I, 1.62 vs. 2.08 g/l; apoB, 0.91 vs. 1.04 g/l; apoM, 0.72 vs. 0.91 mumol/l (p<0.0001 for all three). In multivariate analyses, apoA-I and apoB were associated with AAA, odds ratios (95% confidence intervals) being 0.53 (0.43-0.64) and 0.86 (0.75-0.998), respectively. Conclusions: ApoA-I, apoB and apoM levels were significantly lower in patients with AAA than in the control individuals, but only apoA-I and apoB were independently associated to AAA.
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| 4. |
- Ahnström, Josefin, et al.
(author)
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Plasma concentrations of apolipoproteins A-I, B, and M in patients with critical limb ischemia.
- 2010
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In: Clinical Biochemistry. - : Elsevier BV. - 1873-2933 .- 0009-9120. ; 43, s. 599-603
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Journal article (peer-reviewed)abstract
- OBJECTIVES: Apolipoproteins affect development of atherosclerosis, but their involvement in the pathogenesis of critical limb ischemia (CLI), a severe form of atherosclerosis, has not previously been examined. DESIGN AND METHODS: ApoA-I, apoB, and apoM were measured in plasma from 196 CLI subjects and 214 control individuals from the background population. RESULTS: Cases had lower levels of the apolipoproteins, as compared to controls; apoA-I, 1.23 vs. 2.08 g/L; apoB, 0.93 vs. 1.04 g/L; apoM, 0.75 vs. 0.91 mumol/L (p<0.0001 for all three). ApoA-I and apoM correlated negatively with inflammatory markers and positively to 1- and 3-year survival rates, whereas apoB did not. In multivariate analyses, apoA-I, but not apoB and apoM, was independently associated with CLI, the odds ratio being 0.015. CONCLUSIONS: In subjects with CLI, plasma concentrations of apoA-I, apoB and apoM were significantly lower than in control individuals, but only apoA-I was independently associated to CLI.
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| 5. |
- Ahnström, Josefin, et al.
(author)
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Plasma levels of apolipoprotein M in normal and complicated pregnancy.
- 2010
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In: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 1600-0412 .- 0001-6349. ; 89:9, s. 1214-1217
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Journal article (peer-reviewed)abstract
- Apolipoprotein M (apoM) is mainly associated with high-density lipoprotein in human plasma. Despite several studies suggesting apoM as an anti-atherogenic, its function is not yet fully understood. Plasma apoM was measured in normal pregnancies at four different gestational ages and in the postpartum period to investigate whether the concentration of apoM changes during pregnancy. In addition, apoM was measured at 13 weeks in women who subsequently developed preeclampsia, gestational diabetes, recurrent miscarriage, or small-for-gestational age babies, and in women with uncomplicated pregnancies. The plasma concentrations of apoM increased during pregnancy to reach highest levels in the postpartum period. Thus, plasma apoM in non-pregnant women was around 0.77 micromol/l, 0.88 micromol/l at 40 gestational weeks, and 1.05 micromol/l in the postpartum period (p < 0.0001). No differences in plasma concentrations of apoM were found among the studied pregnancy complications.
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| 6. |
- Andersson, Helena M., et al.
(author)
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Activated protein C cofactor function of protein S: a critical role for Asp95 in the EGF1-like domain
- 2010
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 115:23, s. 4878-4885
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Journal article (peer-reviewed)abstract
- Protein S has an established role in the protein C anticoagulant pathway, where it enhances the factor Va (FVa) and factor VIIIa (FVIIIa) inactivating property of activated protein C (APC). Despite its physiological role and clinical importance, the molecular basis of its action is not fully understood. To clarify the mechanism of the protein S interaction with APC, we have constructed and expressed a library of composite or point variants of human protein S, with residue substitutions introduced into the Gla, thrombin-sensitive region (TSR), epidermal growth factor 1 (EGF1), and EGF2 domains. Cofactor activity for APC was evaluated by calibrated automated thrombography (CAT) using protein S-deficient plasma. Of 27 variants tested initially, only one, protein S D95A (within the EGF1 domain), was largely devoid of functional APC cofactor activity. Protein S D95A was, however, gamma-carboxylated and bound phospholipids with an apparent dissociation constant (Kd(app)) similar to that of wildtype (WT) protein S. In a purified assay using FVa R506Q/R679Q, purified protein S D95A was shown to have greatly reduced ability to enhance APC-induced cleavage of FVa Arg306. It is concluded that residue Asp95 within EGF1 is critical forAPC cofactor function of protein S and could define a principal functional interaction site for APC. (Blood. 2010;115(23):4878-4885)
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| 7. |
- Berggren, Peter, 1971-, et al.
(author)
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Statistical modelling of team training in a microworld study
- 2014
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In: Proceedings of the Human Factors and Ergonomics Society Annual Meeting. - : Sage Publications. - 2169-5067. ; , s. 894-898
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Conference paper (peer-reviewed)abstract
- A command and control environment is a dynamic and complex setting with complicated technical systems where teams of operators interact to reach shared goals. This study presents an experiment in which we, by means of Structural Equation Modeling (SEM), explain the relations between basic concepts of command and control environments: mental workload, frustration, situational awareness, and performance. This paper reports a LISREL analysis of the Baroutsi, Berggren, Nählinder, & Johansson (2013) data. From that data, a new latent variable “Frustration” emerges, which now can be included in the model.
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| 8. |
- Berggren, Peter, 1971-, et al.
(author)
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The shared priorities measure as a way of assessing team strategic awareness : a bridge between self-assessment and the deep blue sea of field recordings
- 2014
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In: Proceedings of the 2014 European Conference on Cognitive Ergonomics. - New York, NY, USA : ACM Digital Library. - 9781450328746 ; , s. 13-
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Conference paper (peer-reviewed)abstract
- Objective, easy to use, easy to comprehend, high face-validity assessment methods for measuring shared awareness in teams are hard to find. This paper describes an experiment where a new measure called Shared Priorities, which is based on ranking of self-generated strategic items, is tested. Trained teams were compared to non-trained teams in a dynamic problem-solving task in terms of performance and shared awareness. The shared priorities measure was used alongside other, well-documented measures of team awareness based on self-rating. The results show that the Shared Priorities measure correlate with performance and could also distinguish between trained and non-trained teams. However, the Shared Priorities measure did not correlate with the other team measures, suggesting that it captures a different quality of team work than the self-rating measures. Further, the shared priorities measure was found to be easily administered and gained a high user acceptance.
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| 9. |
- Calzavarini, Sara, et al.
(author)
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Molecular basis of coagulation factor V deficiency caused by the R1698W inter-domain mutation
- 2013
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In: Thrombosis and Haemostasis. - 0340-6245. ; 110:1, s. 31-38
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Journal article (peer-reviewed)abstract
- Coagulation factor V (FV) deficiency is characterised by variable bleeding phenotypes and heterogeneous mutations. To add new insights into the FV genotype-phenotype relationship, we characterised the R1698W change in the A3 domain, at the poorly investigated interface with the A2 domain. The FV R1698W mutation was responsible for a markedly reduced expression level (10% of FV-WT) and specific activity in thrombin generation (0.39). Interestingly, the FVa1698W showed rapid activity decay upon activation due to increased dissociation rate between the heavy and light chains. The importance of the size and charge of the residue at position 1698 was investigated by three additional recombinant mutants, FVR1698A, FVR1698Q, and FVR1698E. FVR1698A and FVR1698Q expression (30 and 45% of FV-WT), specific activity (both 0.57) and stability were all reduced. Noticeably, FVR1698E showed normal activity and stability despite poor expression (10% of FV-WT). These data indicate the essential role of R1698 for normal biosynthetic process and support local flexibility for positively or negatively charged residues to produce stable and functional A3-A2 domain interactions. Their experimental alteration produces a gradient of FV defects, which help to interpret the wide spectrum of phenotypes in FV-deficient patients.
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| 10. |
- Carlsson, Sofia, et al.
(author)
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Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the β-Chain of C4b-binding Protein
- 2010
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In: Journal of Biological Chemistry. - : The American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 285:42, s. 32038-32046
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Journal article (peer-reviewed)abstract
- The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 α-chains and 1 β-chain (C4BPβ+), the chains being linked by disulfide bridges. PS binds to the β-chain with high affinity. In plasma, PS is in molar excess over C4BPβ+ and due to the high affinity, all C4BPβ+ molecules contain a bound PS. Taken together with the observation that PS-deficient patients have decreased levels of C4BPβ+, this raises the question of whether PS is important for secretion of the β-chain from the cell. To test this hypothesis, HEK293 cells were stably and transiently transfected with β-chain cDNA in combinations with cDNAs for PS and/or the α-chain. The concentration of β-chains in the medium increased after co-transfection with PS cDNA, but not by α-chain cDNA, suggesting secretion of the β-chains from the cells to be dependent on concomitant synthesis of PS, but not of the α-chains. Thus, β-chains that were not disulfide-linked to the α-chains were secreted in complex with PS, either as monomers or dimers. Pulse-chase demonstrated that the complexes between PS and β-chain were formed intracellularly, in the endoplasmic reticulum. In conclusion, our results demonstrate that successful secretion of β-chains depends on intracellular complex formation with PS, but not on the α-chains. This provides an explanation for the decreased β-chain levels observed in PS-deficient patients.
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