Sieber Matthias, Karanik Magdalena, Brandt Claudia, Blex Christian, Podtschaske Miriam, Erdmann Frank, Rost Rene, Serfling Edgar, Liebscher Jürgen, Pätzel Michael, Radbruch Andreas, Fischer Gunter, Baumgrass Ria
Deutsches Rheuma-Forschungszentrum Berlin, Berlin, Germany.
Eur J Immunol. 2007 Sep;37(9):2617-26. doi: 10.1002/eji.200737087.
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.
钙调神经磷酸酶是一种依赖于Ca(2+) - 钙调蛋白的丝氨酸/苏氨酸蛋白磷酸酶，其对NFAT的去磷酸化作用是T细胞受体依赖性T细胞活化的一个瓶颈。免疫抑制剂环孢素A（CsA）和他克莫司（FK506）在与亲免素形成的二聚体复合物中，通过抑制钙调神经磷酸酶的酶活性来阻断这一过程。我们已鉴定出吡唑并嘧啶化合物NCI3是一种新型的钙调神经磷酸酶 - NFAT信号通路抑制剂。与CsA和FK506相似，NCI3抑制NFAT的去磷酸化和核转位、IL - 2的产生以及受刺激的人原代T细胞的增殖，其IC(50)值为2至4.5 microM。然而，与CsA和FK506不同的是，NCI3既不阻断钙调神经磷酸酶的磷酸酶活性，也不需要亲免素来抑制NFAT活化。我们的数据表明，NCI3与钙调神经磷酸酶结合并引起变构变化，在体内而非体外干扰NFAT的去磷酸化。NCI3不仅作用于内源性钙调神经磷酸酶，还作用于C末端截短的、组成型激活的钙调神经磷酸酶版本。本文所述的新型抑制剂将有助于更好地界定钙调神经磷酸酶激活的细胞调控机制，并可能作为开发新型免疫抑制剂的先导，这类抑制剂并非通过直接抑制钙调神经磷酸酶的磷酸酶活性起作用。
