Identification of a peptide fragment of DSCR1 that competitively inhibits calcineurin activity in vitro and in vivo.

Calcineurin phosphatase activity regulates the nuclear localization of the nuclear factor of activated T cells (NFAT) family of transcription factors during immune challenge. Calcineurin inhibitors, such as the cyclosporin A-cyclophilin A and FK506-FKBP12 complexes, regulate this enzymatic activity noncompetitively by binding at a site distinct from the enzyme active site. A family of endogenous protein inhibitors of calcineurin was recently identified and shown to block calcineurin-mediated NFAT nuclear localization and transcriptional activation. One such inhibitor, Down Syndrome Critical Region 1 (DSCR1), functions in T cell activation, cardiac hypertrophy, and angiogenesis. We have identified a small region of DSCR1 that is a potent inhibitor of calcineurin activity in vitro and in vivo.