Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
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Tributylhexadecylphosphonium Bromide, a Novel Nuclear Factor of Activated T Cells Signaling Inhibitor, Blocks Interleukin-2 Induction Associated with Inhibition of p70 Ribosomal Protein S6 Kinase Phosphorylation
Hiroshi UmeharaAkira Asai
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2012 Volume 35 Issue 5 Pages 805-809

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Abstract

Transcriptional factors of the nuclear factor of activated T cells (NFAT) family are involved in T cell signaling. Many NFAT signaling inhibitors, such as cyclosporin A (CsA) and tacrolimus, abrogate dephosphorylation of NFAT proteins by inhibiting calcineurin activity. In pursuit of a novel type of NFAT signaling inhibitor, we screened our chemical library using the NFAT-dependent reporter assay and identified tributylhexadecylphosphonium bromide (THPB) as a selective NFAT signaling inhibitor. THPB inhibited NFAT-dependent reporter activity, and the induction of interleukin-2 (IL-2) at both mRNA and protein levels by calcium stimulation. Moreover, THPB had an additive effect on the inhibition of IL-2 induction with CsA. Unlike CsA, THPB did not affect dephosphorylation of NFAT1, but suppressed phosphorylation of p70 ribosomal protein S6 kinase (p70S6K). These results suggest that THPB may be a novel type of NFAT signaling inhibitor that acts in association with inhibition of p70S6K phosphorylation.

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© 2012 The Pharmaceutical Society of Japan
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