Functional characterization of the calcipressin 1 motif that suppresses calcineurin-mediated NFAT-dependent cytokine gene expression in human T cells.

Inhibition of the calcineurin-NFAT signalling pathway is one of the main challenges for immunosuppression therapy to avoid the severe side effects of the current anticalcineurinic drugs, cyclosporin A and FK506. The members of the calcipressin family are endogenous inhibitors of calcineurin. We describe for the first time that two independent motifs within human calcipressin 1, the ELHA and the PxIxxT motifs, interact with calcineurin in an independent functional manner. However, the main finding here is that the ELHA-containing calcineurin-inhibitor CALP1 (CIC) motif is the responsible for the in vivo inhibition of calcineurin-mediated NFAT-dependent cytokine gene expression in human T cells. We believe that the identification of the CIC motif could be used as a starting point for the development of new immunosuppressive drugs for use in transplantation and autoimmune diseases.