Calcium-dependent, calmodulin-stimulated protein phosphatase which plays an essential role in the transduction of intracellular Ca2+-mediated signals. Dephosphorylates and activates transcription factor NFATC1. Dephosphorylates and inactivates transcription factor ELK1.Dephosphorylates DARPP32. Negatively regulates MAP3K14/NIK signaling via inhibition of nuclear translocation of the transcription factors RELA and RELB. May play a role in skeletal muscle fiber type specification. Forms a complex composed of a calmodulin-dependent catalytic subunit (also known as calcineurin A) and a regulatory Ca2+-binding subunit (also known as calcineurin B). There are three catalytic subunits, each encoded by a separate gene (PPP3CA, PPP3CB, and PPP3CC) and two regulatory subunits which are also encoded by separate genes (PPP3R1 and PPP3R2). In response to an increase in Ca2+ intracellular levels, forms a complex composed of PPP3CB/calcineurin A, calcineurin B and calmodulin. Interacts (via calcineurin B binding domain) with regulatory subunit PPP3R1/calcineurin B. Interacts (via calmodulin-binding domain) with calmodulin; the interaction depends on calmodulin binding to Ca2+. Interacts with SLC12A1.