calcineurin


cal·ci·neu·rin

(kal'sē-nyūr'in), A calcium-dependent serine-threonine phosphatase involved in T-cell signaling transcription; the target of cyclosporine immunosuppression; the reaction cascade in which it resides is referred to as the calcineurin pathway. [calcium + G. neuron, nerve, + -in]

calcineurin

An enzyme which binds Ca2+ and calmodulin, inhibiting calmodulin activity. Calcineurin alters proteins by removing phosphate groups, shortening duration of NMDA channel opening, resulting in synaptic desensitisation of NMDA receptors. Calcineurin activates T cells via transcription factor NFATc (Nuclear Factor of Activated T cell, cytoplasmic) by dephosphorylation. Activated NFATc is translocated into the nucleus, where it upregulates IL-2 expression, and, by extension, the T cell response. Calcineurin is most concentrated in the CNS, and is inhibited by immunophilin ligand, tacrolimus and cyclosporin, both immunosuppressants. Because rejection can be mediated by calcineurin, calcineurin inhibitors (cyclosporine, pimecrolimus and tacrolimus) are used to prevent or manage rejection.

cal·ci·neu·rin

(kal'sē-nūr'in) A calcium-dependent serine-threonine phosphatase involved in T-cell signaling transcription; the reaction cascade in which it resides is referred to as the calcineurin pathway. [calcium + G. neuron, nerve, + -in]