RESUMEN
Inhibition of the calcineurin-NFAT signalling pathway is one of the main challenges for immunosuppression therapy to avoid the severe side effects of the current anticalcineurinic drugs, cyclosporin A and FK506. The members of the calcipressin family are endogenous inhibitors of calcineurin. We describe for the first time that two independent motifs within human calcipressin 1, the ELHA and the PxIxxT motifs, interact with calcineurin in an independent functional manner. However, the main finding here is that the ELHA-containing calcineurin-inhibitor CALP1 (CIC) motif is the responsible for the in vivo inhibition of calcineurin-mediated NFAT-dependent cytokine gene expression in human T cells. We believe that the identification of the CIC motif could be used as a starting point for the development of new immunosuppressive drugs for use in transplantation and autoimmune diseases.
Asunto(s)
Calcineurina/metabolismo , Citocinas/metabolismo , Regulación de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Musculares/metabolismo , Factores de Transcripción NFATC/metabolismo , Linfocitos T/fisiología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Calcineurina/genética , Línea Celular , Citocinas/genética , Proteínas de Unión al ADN , Humanos , Péptidos y Proteínas de Señalización Intracelular/genética , Células Jurkat , Datos de Secuencia Molecular , Proteínas Musculares/genética , Factores de Transcripción NFATC/genética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Alineación de Secuencia , Transducción de Señal/fisiología , Linfocitos T/citologíaRESUMEN
A limited repertoire of PPP family of serine/threonine phosphatases with a highly conserved catalytic domain acts on thousands of protein targets to orchestrate myriad central biological roles. A major structural reorganization of human calcineurin, a ubiquitous Ser/Thr PPP regulated by calcium and calmodulin and targeted by immunosuppressant drugs cyclosporin A and FK506, is unveiled here. The new conformation involves trans- to cis-isomerization of proline in the SAPNY sequence, highly conserved across PPPs, and remodels the main regulatory site where NFATc transcription factors bind. Transitions between cis- and trans-conformations may involve peptidyl prolyl isomerases such as cyclophilin A and FKBP12, which are known to physically interact with and modulate calcineurin even in the absence of immunosuppressant drugs. Alternative conformations in PPPs provide a new perspective on interactions with substrates and other protein partners and may foster development of more specific inhibitors as drug candidates.