| 1. |
- Andersson, Eva, et al.
(författare)
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The metabolism of vitamin A to 3,4-didehydroretinol can be demonstrated in human keratinocytes, melanoma cells and HeLa cells, and is correlated to cellular retinoid-binding protein expression
- 1994
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - : Elsevier BV. - 0167-4889 .- 1879-2596. ; 1224:3, s. 349-354
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Tidskriftsartikel (refereegranskat)abstract
- Conversion of retinol to 3,4-didehydroretinol is probably a rate-limiting step in the formation of 3,4-didehydroretinoic acid, a candidate ligand for nuclear retinoid receptors in human epidermal keratinocytes. To investigate whether this metabolic pathway also exists in other cell systems, we compared the retinoid concentrations and the bioconversion of [3H]retinol to [3H]3,4-didehydroretinol in human primary keratinocytes, human cervical carcinoma (HeLa) cells, human melanoma (JKM86-4) cells, monkey kidney epithelium (CV-1) cells, and murine teratocarcinoma (F9) cells. The cellular retinol concentration ranged from 2.33 to 99.1 pmol/mg protein with the highest values observed in keratinocytes. 3,4-Didehydroretinol was only detected in cells of human origin and its concentration ranged from 0.24 pmol/mg in HeLa to 34.6 pmol/mg in the keratinocytes. Incubation with [3H]retinol for 1–24 h resulted in a rapid appearance of [3H]3,4-didehydroretinol in human keratinocytes, and to a lesser extent in HeLa and melanoma cells, but not in the other cells. Analysis of cellular retinol- and retinoic acid-binding protein concentrations showed a correlation to the cells' ability to accumulate 3,4-didehydroretinol, suggesting a role for these proteins in the 3,4-didehydro metabolic pathway. The combined results suggest that although 3,4-didehydroretinol is most typical for human keratinocytes, studies of its metabolism are also feasible in HeLa cells which contain low levels of retinoid-binding proteins.
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| 2. |
- Emanuelsson, Olof, et al.
(författare)
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Prediction of organellar targeting signals.
- 2001
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 1541:1-2, s. 114-119
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Tidskriftsartikel (refereegranskat)abstract
- The subcellular location of a protein is an important characteristic with functional implications, and hence the problem of predicting subcellular localization from the amino acid sequence has received a fair amount of attention from the bioinformatics community. This review attempts to summarize the present state of the art in the field.
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| 3. |
- Eriksson, S, et al.
(författare)
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Matrix association of early- and late-replicating chromatin studied by single-cell electrophoresis
- 2002
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 1590:1-3, s. 103-108
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Tidskriftsartikel (refereegranskat)abstract
- CHO-K1 cells were synchronized at the G(1)/S border by mitotic shake-off and aphidicolin incubation. Pulse-labeling with tritium was done at 30 min, 2 or 5 h into the S-phase, with chase incubations for different times in non-radioactive medium. The cells were subjected to neutral microelectrophoresis to extend the DNA into "comets," after which the label was visualized through autoradiography. At zero chase time, all label was positioned in the head. The displacement of label into the tails increased with time, reaching a maximum at about 5 h after the pulse. A lag phase of 2 - 3 It was observed for the early-labeled cells before the displacement started. Also, more label was released after overnight serum starvation, but this was reversed through a 3-h incubation at normal growth conditions. It was found that late-replicating chromatin is organized in larger domains than early-replicating chromatin, and DNA polymerase seems to be an important organizer. Early-replicating chromatin has other important attachments to the nuclear matrix, dependent on metabolic activity.
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| 4. |
- Helander, Anders, et al.
(författare)
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Mechanisms for Plasma‑Mediated Activation of Human Blood Cell Aldehyde Dehydrogenase
- 1992
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 1136:3, s. 259-264
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Tidskriftsartikel (refereegranskat)abstract
- Aldehyde dehydrogenase (ALDH; EC 1.2.1.3) activity assays were carried out on isolated human blood cells in phosphate-buffered saline (PBS) and in PBS mixed with human plasma. In assays with intact erythrocytes or sonicated leukocytes, the presence of 50% (v/v) or greater of plasma in the reaction mixtures produced a 2-fold increase in the rate of aldehyde oxidation. In corresponding assays with sonicated erythrocyte samples, the ALDH activity was enhanced on an average 1.5-fold, whereas a slight decrease was observed in assays with intact leukocytes. The ALDH inhibitor disulfiram almost completely abolished the enzyme activity both in the absence and presence of plasma. In assays with sonicated leukocytes, the activation effect could be antagonized by EDTA, indicating that it was caused largely by divalent cations. With sonicated erythrocytes, a significantly reduced ALDH activity was found only with the highest concentration of EDTA tested, and since a similar reduction was obtained also when plasma was omitted, the plasma-mediated activation of erythrocyte ALDH was suggested to be due to a different mechanism. After separation of plasma by gel filtration, an active fraction was identified by GC-MS and 1H-NMR to contain pyruvic acid, lactic acid and glucose. When tested at physiological plasma concentrations, pyruvic acid caused an increase in erythrocyte ALDH activity similar to that obtained with plasma, while lactic acid and glucose did not. Pyruvic acid did not activate the leukocyte ALDH. Based on these results, it is indicated that the plasma-mediated activation of erythrocyte ALDH is due to pyruvic acid, which reoxidizes NADH via lactate dehydrogenase (EC 1.1.1.27) and, thereby, increases the rate of dissociation of NADH from the terminal enzyme-NADH complex, the rate-limiting step in the ALDH pathway.
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| 5. |
- Lindmark, Maria, 1972-, et al.
(författare)
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Synaptotagmin II could confer Ca(2+) sensitivity to phagocytosis in human neutrophils.
- 2002
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Ingår i: Biochimica et biophysica acta. - 0006-3002. ; 1590:1-3, s. 159-166
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Tidskriftsartikel (refereegranskat)abstract
- Phagolysosome fusion and granule exocytosis in neutrophils are calcium-dependent processes. The calcium requirements vary between granule types, suggesting the presence of different calcium sensors. The synaptotagmins, a family of calcium-binding proteins, previously shown to participate in vesicle fusion and vesicle recycling in excitable cells, are putative calcium-sensors of exocytosis in excitable cells. In this study, we show that synaptotagmin II is present in human neutrophils and may participate in phagocytic and in exocytotic processes. In protein extracts from human neutrophils, we identified synaptotagmin II by Western blot as an 80 kDa protein. Subcellular fractionation revealed that synaptotagmin II was associated with the specific granules. In fMLP-stimulated cells, synaptotagmin II translocated to the plasma membrane. This correlated with the upregulation of complement receptor 3 (CR 3), reflecting the translocation of specific granules to the cell surface. Synaptotagmin II also translocated to the phagosome after complement-mediated phagocytosis in the presence of calcium. LAMP-1 translocated in parallel but probably was located to another subcellular compartment than synaptotagmin II. Under calcium-reduced conditions, neither synaptotagmin II nor LAMP-1 translocated to the phagosome. We therefore suggest a role for synaptotagmin II as calcium-sensor during phagocytosis and secretion in neutrophils.
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| 6. |
- Lundqvist, Helen, et al.
(författare)
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Neutrophil control of formylmethionyl-leucyl-phenylalanine induced mobilization of secretory vesicles and NADPH-oxidase activation: Effect of an association of the ligand-receptor complex to the cytoskeleton
- 1994
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - : Elsevier. - 0167-4889 .- 1879-2596. ; 1224:1, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- The stimulus formylmethionyl-leucyl-phenylalanine (FMLP) interacts with neutrophils and generates signal(s) in the cells that induces mobilization of the secretory vesicles as well as activation of the superoxide anion/hydrogen peroxide generating NADPH-oxidase. Binding, at 15°C, of FMLP to its neutrophil surface receptor is followed by an association of the ligand-receptor complex to the cell cytoskeleton, and this association occurs concomitant with a desensitization of the cells with respect to activation of the NADPH-oxidase. Other stimuli can still activate the oxidase (in fact even induce a primed response), indicating that the observed phenomenon is stimulus specific and could not be accounted for by an effect on the oxidase itself, but rather that the association of the ligand-receptor complex to the cytoskeleton eliminates the capacity of the complex to generate the signal(s) that activates the NADPH-oxidase. The cytoskeleton associated ligand-receptor complex generates, however, the signal(s) responsible for mobilization of the secretory vesicles, to the plasma membrane, and this mobilization occurs without any increase in the intracellular concentration of free Ca2+.
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| 7. |
- Löfgren, Ragnhild, et al.
(författare)
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CR3, FcγRIIA and FcγRIIIB induce activation of the respiratory burst in human neutrophils : the role of intracellular Ca2+, phospholipase D and tyrosine phosphorylation
- 1999
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 1452:1, s. 46-59
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Tidskriftsartikel (refereegranskat)abstract
- Human neutrophils express two different types of phagocytic receptors, complement receptors (CR) and Fc receptors. In order to characterize the different signaling properties of each receptor we have used non-adherent human neutrophils and investigated CR3, FcγRIIA and FcγRIIIB for their signaling capacity. Selective activation of each receptor was achieved by coupling specific antibodies to heat-killed Staphylococcus aureus particles, Pansorbins, through their Fc moiety. Despite the fact that these particles are not phagocytosed, we show that addition of Pansorbins with anti-CD18 antibodies recognizing CR3 induced prominent signals leading to a respiratory burst. Stimulation with anti-FcγRIIIB Pansorbins induced about half of the response induced by anti-CR3 Pansorbins, whereas anti-FcγRIIA Pansorbins induced an even weaker signal. However, FcγRIIA induced strong phosphorylation of p72syk whereas FcγRIIIB induced only a very weak p72syk phosphorylation. During CR3 stimulation no tyrosine phosphorylation of p72syk was seen. Both phospholipase D and NADPH oxidase activities were dependent on intracellular calcium. This is in contrast to tyrosine phosphorylation of p72syk that occurred even in calcium-depleted cells, indicating that oxygen metabolism does not affect p72syk phosphorylation. Inhibitors of tyrosine phosphorylation blocked the respiratory burst induced by both FcγRIIA and FcγRIIIB as well as CR3. This shows that tyrosine phosphorylation of p72syk is an early signal in the cascade induced by FcγRIIA but not by CR3.
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| 8. |
- Nilsson Ekdahl, Kristina, et al.
(författare)
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Effects of epinephrine, glucagon and insulin on the activity and degree of phosphorylation of fructose-1,6-bisphosphatase in cultured hepatocytes.
- 1987
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 929:3, s. 318-326
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Tidskriftsartikel (refereegranskat)abstract
- The effects of epinephrine, glucagon and insulin on the activity and degree of phosphorylation of fructose-1,6-bisphosphatase in isolated hepatocytes maintained in cell culture for 24 h were investigated. Epinephrine caused a rapid decrease in the apparent Km monitored as the activity ratio between the activity at 12.5 and 83 microM fructose-1,6-bisphosphate, reaching a maximum after 5 min. Glucagon caused a slower and less pronounced activation, and insulin caused an equally slow increase in Km. The effect of epinephrine and glucagon was completely reciprocated by insulin and the action of insulin was totally erased by the other two. Glucagon stimulated the incorporation of [32P]phosphate into fructose-1,6-bisphosphatase from about 2.5 to 4.2 mol/mol enzyme and epinephrine to 3.5 mol/mol. The effect of the two hormones acting together was cumulative. Insulin brought about a decrease in the degree of phosphorylation to 2.0 mol/mol. The effect of epinephrine was shown to be caused by the beta-receptors, since it was completely blocked by propanolol (a beta-antagonist) and remained unaffected by the presence of phentolamine (an alpha-antagonist).
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| 9. |
- Serrander, Lena, et al.
(författare)
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Particles binding β2-integrins mediate intracellular production of oxidative metabolites in human neutrophils independently of phagocytosis
- 1999
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - 0167-4889 .- 1879-2596. ; 1452:2, s. 133-144
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Tidskriftsartikel (refereegranskat)abstract
- Complement-opsonised particles are readily ingested by human neutrophils through a complement receptor-mediated process leading to phagolysosome fusion and production of oxidative metabolites. To investigate the complement receptor 3 (CR3)-associated signal system involved, cells were challenged with protein A-positive, heat-killed Staphylococcus aureus to which antibodies with specificity for the subunits of the β2-integrins, i.e. anti-CD11b (the α subunit of CR3) and anti-CD18 (the β subunit of CR3), were bound through their Fc moiety. Despite not being ingested by the neutrophils, the surface associated anti-CD18- and anti-CD11b-coated particles were able to activate the neutrophil NADPH-oxidase. Also anti-CD11a- (the α subunit of LFA-1) and to a lesser extent anti-CD11c- (the α subunit of CR4) coated particles were able to trigger the NADPH-oxidase. The NADPH-oxidase was activated without extracellular release of reactive oxygen species. The activity was inhibited by cytochalasin B, suggesting a necessary role for the cytoskeleton in the signalling pathway that activates the oxidase. We show that particle-mediated cross-linking of β2-integrins on the neutrophil surface initiates a signalling cascade, involving cytoskeletal rearrangements, leading to an activation of the NADPH-oxidase without phagosome formation or extracellular release of reactive oxygen species.
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| 10. |
- Al-Furoukh, Natalie, et al.
(författare)
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ClpX stimulates the mitochondrial unfolded protein response (UPRmt) in mammalian cells
- 2015
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Ingår i: Biochimica et Biophysica Acta. Molecular Cell Research. - : Elsevier BV. - 0167-4889 .- 1879-2596. ; 1853:10, s. 2580-2591
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Tidskriftsartikel (refereegranskat)abstract
- Proteostasis is crucial for life and maintained by cellular chaperones and proteases. One major mitochondrial protease is the ClpXP complex, which is comprised of a catalytic ClpX subunit and a proteolytic ClpP subunit. Based on two separate observations, we hypothesized that ClpX may play a leading role in the cellular function of ClpXP. Therefore, we analyzed the effect of ClpX overexpression on a myoblast proteome by quantitative proteomics. ClpX overexpression results in the upregulation of markers of the mitochondria( proteostasis pathway, known as the "mitochondrial unfolded protein response" (UPRmt). Although this pathway is described in detail in Caenorhabditis elegans, it is not clear whether it is conserved in mammals. Therefore, we compared features of the classical nematode UPRmt with our mammalian ClpX-triggered UPRmt dataset. We show that they share the same retrograde mitochondria-to-nucleus signaling pathway that involves the key UPRmt transcription factor CHOP (also known as Ddit3, CEBPZ or GADD153). In conclusion, our data confirm the existence of a mammalian UPRmt that has great similarity to the C elegans pathway. Furthermore, our results illustrate that ClpX overexpression is a good and simple model to study the underlying mechanisms of the UPRmt in mammalian cells.
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