Protein phosphatase 2B (Calcineurin) (CN)

Protein phosphatase 2B, commonly known as calcineurin, is a calcium- and calmodulin-dependent serine/threonine phosphatase that serves as a critical transducer of calcium signals in various tissues (StatPearls, 2023). It is best known for its role in the immune system, where it dephosphorylates the nuclear factor of activated T-cells (NFAT), enabling its translocation into the nucleus to induce the transcription of interleukin-2 and other cytokines essential for T-cell activation and proliferation (UniProt, 2024). Because of this central role, calcineurin is the primary therapeutic target for major immunosuppressive drugs such as tacrolimus and cyclosporine, which are fundamental in preventing allograft rejection in organ transplantation and managing autoimmune disorders. Beyond immunology, calcineurin signaling regulates cardiac hypertrophy, skeletal muscle development, and neuronal function, making it a focus of research in cardiovascular and neurodegenerative diseases (Nature Reviews Molecular Cell Biology, 2009). However, therapeutic modulation of this pathway is challenged by narrow therapeutic windows and significant side effects, most notably dose-dependent nephrotoxicity and metabolic complications. This entry is marked as incorrect because the provided term 'Calcineurin signaling pathway' describes a biological process rather than a specific molecular target, which is the calcineurin enzyme itself.

Other names

CalcineurinCaNPP2BPPP3CAPPP3CBPPP3CCCalcium/calmodulin-dependent serine-threonine protein phosphatase

Inhibition of the phosphatase activity of calcineurin through the formation of a drug-immunophilin complex (drug binding to cyclophilin or FKBP12), which sterically hinders the active site of calcineurin, preventing the dephosphorylation and nuclear translocation of NFAT and subsequent cytokine production (StatPearls, 2023).