title: Effect of TGFβ on calcium signaling in megakaryocytes.
abstract: TGFβ is a powerful regulator of megakaryocyte maturation and platelet formation. As previously shown for other cell types, TGFβ may up-regulate the expression of the serum & glucocorticoid inducible kinase SGK1, an effect requiring p38 kinase. SGK1 has in turn recently been shown to participate in the regulation of cytosolic Ca(2+) activity ([Ca(2+)]i) in megakaryocytes and platelets. SGK1 phosphorylates the IκB kinase (IKKα/β), which in turn phosphorylates the inhibitor protein IκBα resulting in nuclear translocation of nuclear factor NFκB. Genes up-regulated by NFκB include Orai1, the pore forming ion channel subunit accomplishing store operated Ca(2+) entry (SOCE). The present study explored whether TGFβ influences Ca(2+) signaling in megakaryocytes. [Ca(2+)]i was determined by Fura-2 fluorescence and SOCE from the increase of [Ca(2+)]i following re-addition of extracellular Ca(2+) after store depletion by removal of extracellular Ca(2+) and inhibition of the sarcoendoplasmatic Ca(2+) ATPase (SERCA) with thapsigargin (1 μM). As a result, TGFβ (60 ng, 24 h) increased SOCE, an effect significantly blunted by p38 kinase inhibitor Skepinone-L (1 μM), SGK1 inhibitor EMD638683 (50 μM) and NFκB inhibitor wogonin (100 μM). In conclusion, TGFβ is a powerful regulator of store operated Ca(2+) entry into megakaryocytes, an effect mediated by a signaling cascade involving p38 kinase, SGK1 and NFκB.
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors: Jing
authors: J
authors: Yan
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany; Department of Pediatric Surgery and Pediatric Urology, University Children's Hospital Tübingen, Tübingen, Germany.
authors: Evi
authors: E
authors: Schmid
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors: Ahmad
authors: A
authors: Almilaji
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors: Ekaterina
authors: E
authors: Shumilina
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany; Department of Cardiology & Cardiovascular Medicine, University of Tübingen, Tübingen, Germany.
authors: Oliver
authors: O
authors: Borst
authors: Department of Pharmacy, University of Tübingen, Tübingen, Germany.
authors: Stefan
authors: S
authors: Laufer
authors: Department of Cardiology & Cardiovascular Medicine, University of Tübingen, Tübingen, Germany.
authors: Meinrad
authors: M
authors: Gawaz
authors: Department of Physiology I, University of Tübingen, Tübingen, Germany. Electronic address: florian.lang@uni-tuebingen.de.
authors: Florian
authors: F
authors: Lang
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D008533:Megakaryocytes / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D016212:Transforming Growth Factor beta; D002118:Calcium
keywords: NF-κB; SGK1; SOCE; p38 kinase