Inhibition of calcineurin-NFAT signaling by the pyrazolopyrimidine compound NCI3.
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.
Sieber
Matthias
M
Deutsches Rheuma-Forschungszentrum Berlin, Berlin, Germany.
Karanik
Magdalena
M
Brandt
Claudia
C
Blex
Christian
C
Podtschaske
Miriam
M
Erdmann
Frank
F
Rost
Rene
R
Serfling
Edgar
E
Liebscher
Jürgen
J
Pätzel
Michael
M
Radbruch
Andreas
A
Fischer
Gunter
G
Baumgrass
Ria
R
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
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