PPP3R1, also known as Calcineurin subunit B type 1, is a Ser/Thr-specific calcium and calmodulin-dependent protein phosphatase that plays an essential role in the T cell activation pathway. Calcineurin is composed of two subunits; calcineurin A (CnA) and calcineurin B (CnB). Dephosphorylation of the nuclear factor of activated T-cells (NF-AT) by Calcineurin is essential for NF-AT activation, nuclear translocation, and early gene expression in T-cells.