Calcineurin (CN) is a protein phosphatase also known as protein phosphatase 2B (PP2B). Is responsible for activating the transcription of IL-2, that stimulates the growth and differentiation of T cell response. In immunosuppressive therapy it is inhibited by ciclosporin and tacrolimus (FK506) - these drugs are known as calcineurin inhibitors. Calcineurin dephosphorylates NFATc, a transcription factor that can then go into the nucleus and turn on genes involved in heart valve elongation.

Mechanism of action

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When T-helper cell's receptor interacts with an antigen, the intracellular concentration of calcium in the cell rises. This increase activates calcineurin. Calcineurin induces different transcription factors that are important in the transcription of IL-2 genes. IL-2 activates T-helper lymphocytes and induces the production of other cytokines. In this way, it governs the action of cytotoxic lymphocytes and NK cells. The amount of IL-2 being produced by the T-helper cells is believed to influence the extent of the immune response significantly.

Enzymes | signal transduction

Calcineurine