The present invention relates to peptides and polypeptides having the sequence SAVTFAVCAL or variants thereof, capable of binding to Calcineurin and/or to NS5A-TP2 and to their use in therapy, as well as to nucleic acid sequences and vectors encoding these peptides and polypeptides, and to cells comprising said polypeptides, nucleic acid sequences or vectors. The invention further relates to the use of the peptides, polypeptides or their derivatives to bring about phenotypic changes in mammalian cells, particularly to up-regulate calcineurin activity. The invention finally relates to a method for intracellular identification of substances which bind to calcineurin and which modulate the physiological effects of calcineurin.