Regulation of Down Syndrome Critical Region 1 expression by Nuclear Factor of Activated T cells in megakaryocytes.
As precursors of platelets, megakaryocytes must fulfil the complex tasks of protein synthesis and platelet assembly. Megakaryocytic dysfunction can lead to neoplastic disorders, such as acute megakaryoblastic leukaemia, an entity with a 500-fold increased incidence in children with Down syndrome (DS). Down Syndrome Critical Region 1 (DSCR1), a member of the calcipressin family of calcineurin inhibitors, is overexpressed in DS, and destabilization of the calcineurin/Nuclear Factor of Activated T cells (NFAT) pathway by overexpression of DSCR1 has been implicated in some of the pathophysiological features of the disease. The roles of NFAT and DSCR1 in megakaryocyte signalling and gene expression, however, are unknown. In this study, we show that calcineurin and NFAT are components of a calcium-induced signalling cascade in megakaryocytes. NFAT activation in megakaryocytes was induced by fibrillar collagen type I and was completely sensitive to the calcineurin inhibitor cyclosporin A. We established DSCR1 as a calcium-induced NFAT target gene in these cells and show that overexpression of DSCR1 in megakaryocytes strongly inhibits NFAT activation as well as NFAT-dependent expression of the Fas ligand gene (FASLG). These results suggest that DSCR1 acts as an endogenous feedback inhibitor of NFAT signalling in megakaryocytes, and may have implications for megakaryocytic gene expression in DS.
Kyttälä
Satu
S
Department of Medicine I, Dresden University of Technology, Dresden, Germany.
Habermann
Ivonne
I
Minami
Takashi
T
Ehninger
Gerhard
G
Kiani
Alexander
A
D015153:Blotting, Western / Q000379:methods; D019703:Calcineurin / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008533:Megakaryocytes / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D050778:NFATC Transcription Factors; C108612:RCAN1 protein, human; D019703:Calcineurin