title: Inhibition of calcineurin-NFAT signaling by the pyrazolopyrimidine compound NCI3.
abstract: Dephosphorylation of NFAT by the Ca(2+)-calmodulin-dependent Ser/Thr protein phosphatase calcineurin is a bottleneck of T cell receptor-dependent activation of T cells. In dimeric complexes with immunophilins, the immunosuppressants cyclosporine A (CsA) and tacrolimus (FK506) block this process by inhibition of the enzymatic activity of calcineurin. We have identified the pyrazolopyrimidine compound NCI3 as a novel inhibitor of calcineurin-NFAT signaling. Similar to CsA and FK506, NCI3 inhibits dephosphorylation and nuclear translocation of NFAT, IL-2 production and proliferation of stimulated human primary T cells with IC(50) values from 2 to 4.5 microM. However, contrary to CsA and FK506, NCI3 neither blocks calcineurin;s phosphatase activity nor requires immunophilins for inhibiting NFAT activation. Our data suggest that NCI3 binds to calcineurin and causes an allosteric change interfering with NFAT dephosphorylation in vivo but not in vitro. NCI3 acts not only on the endogenous calcineurin but also on a C-terminally truncated, constitutively active version of calcineurin. The novel inhibitor described herein will be useful in better defining the cellular regulation of calcineurin activation and may serve as a lead for the development of a new type of immunosuppressants acting not by direct inhibition of the calcineurin phosphatase activity.
authors: Deutsches Rheuma-Forschungszentrum Berlin, Berlin, Germany.
authors: Matthias
authors: M
authors: Sieber
authors: Magdalena
authors: M
authors: Karanik
authors: Claudia
authors: C
authors: Brandt
authors: Christian
authors: C
authors: Blex
authors: Miriam
authors: M
authors: Podtschaske
authors: Frank
authors: F
authors: Erdmann
authors: Rene
authors: R
authors: Rost
authors: Edgar
authors: E
authors: Serfling
authors: Jürgen
authors: J
authors: Liebscher
authors: Michael
authors: M
authors: Pätzel
authors: Andreas
authors: A
authors: Radbruch
authors: Gunter
authors: G
authors: Fischer
authors: Ria
authors: R
authors: Baumgrass
mesh_terms: D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007166:Immunosuppressive Agents / Q000737:chemistry / Q000494:pharmacology; D015394:Molecular Structure; D050778:NFATC Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D011720:Pyrazoles / Q000737:chemistry / Q000494:pharmacology*; D011743:Pyrimidines / Q000737:chemistry / Q000494:pharmacology*; D011948:Receptors, Antigen, T-Cell / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism
chemical_list: D065095:Calcineurin Inhibitors; D007166:Immunosuppressive Agents; C523651:NCI3 compound; D050778:NFATC Transcription Factors; D010446:Peptide Fragments; D011720:Pyrazoles; D011743:Pyrimidines; D011948:Receptors, Antigen, T-Cell; D050807:ets-Domain Protein Elk-1; D000071679:Glycogen Synthase Kinase 3 beta; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D019703:Calcineurin; C030986:pyrimidine