title: Protein kinase CK2-dependent phosphorylation of the human Regulators of Calcineurin reveals a novel mechanism regulating the calcineurin-NFATc signaling pathway.
abstract: Cyclosporine A and FK506 produce immunosuppression by blocking calcineurin phosphatase activity and consequently activation of cytosolic Nuclear Factor of Activated T-cell (NFATc) transcription factor. Due to the chronic toxicity associated with their administration, the development of more specific immunosuppressants is currently an important unmet medical need. In this context, an immunosuppressant peptide derived from the CIC motif of the human Regulators of Calcineurin (RCAN) proteins has been shown to inhibit NFATc signaling without affecting general phosphatase activity of calcineurin. Here we show that protein kinase CK2 phosphorylates a conserved serine residue within the CIC motif of vertebrate RCANs, which increases its affinity for calcineurin and consequently its inhibition of NFATc-dependent gene expression in activated T-cells. Molecular modeling studies have led us to identify a positively charged interaction site on the surface of calcineurin where the phosphorylated serine residue of the CIC motif would normally locate. Finally, we have also identified RCAN3 as a new phosphoprotein with multiple phosphorylation sites. Therefore, our findings reveal for the first time a novel molecular mechanism underlying the regulation of calcineurin-NFATc signaling by means of phosphorylation of the CIC motif of RCAN proteins. The knowledge of how RCAN proteins modulate the calcineurin-NFATc pathway paves the way for the development of potent novel selective immunosuppressant drugs.
authors.affiliation: Bellvitge Biomedical Research Institute - IDIBELL, L'Hospitalet de Llobregat, Barcelona, Catalonia, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Martínez-Høyer
authors.forename: Alvaro
authors.initials: A
authors.lastname: Aranguren-Ibáñez
authors.forename: Javier
authors.initials: J
authors.lastname: García-García
authors.forename: Eva
authors.initials: E
authors.lastname: Serrano-Candelas
authors.forename: Jordi
authors.initials: J
authors.lastname: Vilardell
authors.forename: Virginia
authors.initials: V
authors.lastname: Nunes
authors.forename: Fernando
authors.initials: F
authors.lastname: Aguado
authors.forename: Baldo
authors.initials: B
authors.lastname: Oliva
authors.forename: Emilio
authors.initials: E
authors.lastname: Itarte
authors.forename: Mercè
authors.initials: M
authors.lastname: Pérez-Riba
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D047390:Casein Kinase II / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D002942:Circular Dichroism; D004268:DNA-Binding Proteins; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D050778:NFATC Transcription Factors; C108612:RCAN1 protein, human; D012333:RNA, Messenger; D008156:Luciferases; D047390:Casein Kinase II; D019703:Calcineurin
keywords: CIC sequence; CK2; Calcineurin–NFATc signaling; Cn; CnA; CsA; Immunosuppression; Io; Ionomycin; NFATc; PMA; PXIXIT; Phorbol 12-miristate 13-acetate; Phosphorylation; RCAN; RCAN (formerly calcipressin) inhibitor of calcineurin sequence; Regulators of Calcineurin; calcineurin; calcineurin catalytic subunit A; cyclosporin A; cytosolic Nuclear Factor of Activated T-cells; protein kinase CK2