Calcineurin (CaN) comprises CaN A and CaN B subunits. It exists as a heterodimer with a calmodulin-binding domain, catalytic site, a CaN B binding domain, and an autoinhibitory domain.
Calcineurin is a cyclosporin-sensitive, calcium-regulated, serine-threonine protein phosphatase with broad substrate specificity. It is the major calmodulin-binding protein found in the brain. First identified as an inhibitor of the calmodulin activation of phosphodiesterase 3′:5′ cyclic nucleotide (PDE), calcineurin has similar effects on adenylate cyclase. Serves as a key enzyme involved in T-cell activation. Also involved in the hyperphosphorylation of tau protein in Alzheimer′s disease and has been shown to prevent calpain-mediated proteolysis of tau in differentiated PC12 cells.
