| 1. |
- Gustavsson, Anna, et al.
(author)
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Role of the β1-integrin cytoplasmic tail in mediating invasin-promoted internalization of Yersinia
- 2002
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In: Journal of Cell Science. - : The Company of Biologists Ltd. - 0021-9533 .- 1477-9137. ; 115:13, s. 2669-2678
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Journal article (peer-reviewed)abstract
- Invasin of Yersinia pseudotuberculosis binds to beta1-integrins on host cells and triggers internalization of the bacterium. To elucidate the mechanism behind the beta1-integrin-mediated internalization of Yersinia, a beta1-integrin-deficient cell line, GD25, transfected with wild-type beta1A, beta1B or different mutants of the beta1A subunit was used. Both beta1A and beta1B bound to invasin-expressing bacteria, but only beta1A was able to mediate internalization of the bacteria. The cytoplasmic region of beta1A, differing from beta1B, contains two NPXY motifs surrounding a double threonine site. Exchanging the tyrosines of the two NPXYs to phenylalanines did not inhibit the uptake, whereas a marked reduction was seen when the first tyrosine (Y783) was exchanged to alanine. A similar reduction was seen when the two nearby threonines (TT788-9) were exchanged with alanines. It was also noted that cells affected in bacterial internalization exhibited reduced spreading capability when seeded onto invasin, suggesting a correlation between the internalization of invasin-expressing bacteria and invasin-induced spreading. Likewise, integrins defective in forming peripheral focal complex structures was unable to mediate uptake of invasin-expressing bacteria.
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| 2. |
- Johansson, Maria, et al.
(author)
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Carleman's inequality : history, proofs and some new generalizations
- 2003
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In: Journal of Inequalities in Pure and Applied Mathematics. - 1443-5756. ; 4:3
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Journal article (peer-reviewed)abstract
- Carleman's inequality reads where , are positive numbers. In this paper we present some simple proofs of and several remarks (e.g. historical) about the inequality and its corresponding continuous version. Moreover, we discuss and comment on some very new results. We also include some new proofs and results e.g. a weight characterization of a general weighted Carleman type inequality for the case 0 p q We also include some facts about T. Carleman and his work.
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| 3. |
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| 4. |
- Nilsson, Anna, et al.
(author)
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Tryptophan-tagged cutinase studied by steady state fluorescence for understanding of tag interactions in aqueous two-phase systems
- 2003
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In: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639. ; 1646:1-2, s. 57-66
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Journal article (peer-reviewed)abstract
- Genetic engineering has been used to construct fusion proteins of Fusarium solani pisi cutinase and tryptophan-based tags, expressed in Saccharomyces cerevisiae, to increase the partitioning in aqueous two-phase systems. The separation systems were composed of thermoseparating polymers (random copolymers of ethylene oxide and propylene oxide, EOPO) and detergents (C12EOn). In this study, the fluorescence behaviour of the peptide-tagged protein, free peptide tag and tryptophan was investigated. The tryptophan-tagged proteins, cutinase-(WP)4 and cutinase-TGGSGG-(WP)4, showed emission spectra similar to the free peptides and tryptophan, indicating solvent exposure of the tag. The influence of polymers and detergents on the fluorescence of tagged proteins was examined. When peptides and tagged proteins were exposed to polymer, a slight blue shift of the emission maximum was observed. Larger blue shifts of the emission maximum were observed when C12EOn detergents were utilised. The results correlate with aqueous two-phase partitioning where addition of C12EOn detergents results in more extreme partitioning compared to systems containing only polymers. Dynamic light scattering (DLS) measurements of the EOPO copolymers were carried out, showing that the polymers did not aggregate at concentrations used in aqueous two-phase systems. Quenching of fluorescence with iodide for both proteins and peptide tags was studied. Plots according to the Stern-Volmer equation resulted in a linear fit, indicating exposed tryptophan residues for both free peptides and fusion proteins. The quenching constants were similar for both tagged protein and free peptide tag. The fluorescence results indicated that the tryptophan residues in the tag were exposed to the solvent and could interact with detergents and polymers in the two-phase systems.
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| 5. |
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| 6. |
- Tsuchida, Hiroki, et al.
(author)
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Gene expression of the p85alpha regulatory subunit of phosphatidylinositol 3-kinase in skeletal muscle from type 2 diabetic subjects.
- 2002
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In: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 445:1, s. 25-31
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Journal article (peer-reviewed)abstract
- The gene of the p85alpha regulatory subunit of phosphatidylinositol (PI) 3-kinase gives rise to several splice variants. We hypothesized that the expression of p85alpha splice variants may be altered in skeletal muscle from subjects with type 2 diabetes mellitus. Skeletal muscle biopsies were obtained from nine type 2 diabetic and eight healthy men, matched for age, body mass index (BMI) and physical fitness. PI 3-kinase activity in skeletal muscle following in vitro insulin stimulation was reduced in subjects with type 2 diabetes. p85alpha mRNA was elevated fourfold in type 2 diabetic as compared to healthy control subjects ( P<0.05). p85alpha mRNA abundance was positively correlated with plasma insulin concentration ( P<0.01) and serum glucose concentration ( P<0.01). Despite this, protein levels of p85alpha, p55alpha, and the novel human p50alpha were not altered in type 2 diabetic subjects. Thus, although gene expression of full-length p85alpha is increased in skeletal muscle from type 2 diabetics, this is not reflected by increased protein levels. Therefore, defects in PI 3-kinase activity are likely due to impaired activation of the enzyme rather than changes in protein expression of the isoforms of the regulatory subunit.
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