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- Björnström, Karin, 1971-, et al.
(författare)
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A tyrosine kinase regulates propofol-induced modulation of the beta-subunit of the GABA(A) receptor and release of intracellular calcium in cortical rat neurones
- 2002
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 175:3, s. 227-235
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Tidskriftsartikel (refereegranskat)abstract
- Propofol, an intravenous anaesthetic, has been shown to interact with the beta -subunit of the gamma -amino butyric acid(A) (GABA(A) ) receptor and also to cause changes in [Ca2+ ](i) . The GABA(A) receptor, a suggested target for anaesthetics, is known to be regulated by kinases. We have investigated if tyrosine kinase is involved in the intracellular signal system used by propofol to cause anaesthesia. We used primary cell cultured neurones from newborn rats, pre-incubated with or without a tyrosine kinase inhibitor before propofol stimulation. The effect of propofol on tyrosine phosphorylation and changes in [Ca2+ ](i) were investigated. Propofol (3 mu g mL(-1) , 16.8 mu M) increased intracellular calcium levels by 122 +/- 34% (mean +/- SEM) when applied to neurones in calcium free medium. This rise in [Ca2+ ](i) was lowered by 68% when the cells were pre-incubated with the tyrosine kinase inhibitor herbimycin A before exposure to propofol (P < 0.05). Propofol caused an increase (33 +/- 10%) in tyrosine phosphorylation, with maximum at 120 s, of the beta -subunit of the GABA(A) -receptor. This tyrosine phosphorylation was decreased after pre-treatment with herbimycin A (44 +/- 7%, P < 0.05), and was not affected by the absence of exogenous calcium in the medium. Tyrosine kinase participates in the propofol signalling system by inducing the release of calcium from intracellular stores and by modulating the beta -subunit of the GABA(A) -receptor.
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- Björnström, Karin, 1971-, et al.
(författare)
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Characterisation of the signal transduction cascade caused by propofol in rat neurons : From the GABAA receptor to the cytoskeleton
- 2008
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Ingår i: Journal of Physiology and Pharmacology. - 0867-5910 .- 1899-1505. ; 59:3, s. 617-632
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Tidskriftsartikel (refereegranskat)abstract
- The anaesthetic propofol interacts with the GABAA receptor, but its cellular signalling pathways are not fully understood. Propofol causes reorganisation of the actin cytoskeleton into ring structures in neurons. Is this reorganisation a specific effect of propofol as apposed to GABA, and which cellular pathways are involved? We used fluorescence-marked actin in cultured rat neurons to evaluate the percentage of actin rings caused by propofol or GABA in combination with rho, rho kinase (ROK), PI3-kinase or tyrosine kinase inhibitors, with or without the presence of extracellular calcium. Confocal microscopy was performed on propofol-stimulated cells and changes in actin between cellular compartments were studied with Western blot. Propofol (3 μg·ml-1), but not GABA (5 μM), caused transcellular actin ring formation, that was dependent on influx of extracellular calcium and blocked by rho, ROK, PI3-kinase or tyrosine kinase inhibitors. Propofol uses rho/ROK to translocate actin from the cytoskeleton to the membrane and its actin ring formation is dependent on an interaction site close to the GABA site on the GABAA receptor. GABA does not cause actin rings, implying that this is a specific effect of propofol.
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- Björnström, Karin, 1971-, et al.
(författare)
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The difference between sleep and anaesthesia is in the intracellular signal : propofol and GABA use different subtypes of the GABAA receptor β subunit and vary in their interaction with actin
- 2003
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 47:2, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- Background: Propofol is known to interact with the γ-aminobutyric acidA (GABAA) receptor, however, activating the receptor alone is not sufficient for producing anaesthesia.Methods: To compare propofol and GABA, their interaction with the GABAA receptor β subunit and actin were studied in three cellular fractions of cultured rat neurons using Western blot technique.Results: Propofol tyrosine phosphorylated the GABAA receptor β2 (MW 54 and 56 kDa) and β3 (MW 57 kDa) subtypes. The increase was shown in both the cytoskeleton (β2(54) and β2(56) subtypes) and the cell membrane (β2(54) and β3 subtypes). Concurrently the 56 kDa β2 subtype was reduced in the cytosol. Propofol, but not GABA, also tyrosine phosphorylated actin in the cell membrane and cytoskeletal fraction. Without extracellular calcium available, the amount of actin decreased in the cytoskeleton, but tyrosine phosphorylation was unchanged. GABA caused increased tyrosine phosphorylation of β2(56) and β3 subtypes in the membrane and both β2 subtypes in the cytoskeleton but no cytosolic tyrosine phosphorylation.Conclusion: The difference between propofol and GABA at the GABAA receptor was shown to take place in the membrane, where the β2(54) was increased by propofol and instead the β2(56) subtype was increased by GABA. Only propofol also tyrosine phosphorylated actin in the cell membrane and cytoskeletal fraction. This interaction between the GABAA receptor and actin might explain the difference between anaesthesia and physiological neuronal inhibition.
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