CALCINEURIN - NOT JUST A SIMPLE PROTEIN PHOSPHATASE

Calcineurin is a Ca2+ calmodulin dependent protein phosphatase which h as an important role in the control of intracellular Ca2+ signalling. The protein is a heterodimer of one catalytic (CnA) subunit and one re gulatory (CnB) subunit. As suggested by the protein sequence and confi rmed by the crystallographic structure, the catalytic subunit of calci neurin (CnA) has high homologies with other protein phosphatases. The regulatory subunit (CnB) belongs to the EP-hand Ca2+ binding protein f amily. Despite its similarity with calmodulin, it has a different tert iary structure. Calcineurin is the target of two important immunosuppr essant drugs: cyclosporin A and FK506. Subsequently, a detailed clarif ication of the role of calcineurin in the cytokine mediated activation of the T-cells has been possible. The understanding of the role of ca lcineurin in other cells, in particular neurons, is also progressing r apidly. (C) 1997 Academic Press.