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Identification and characterization of a highly conserved calcineurin binding protein, CBP1/calcipressin, in
J Görlach1, D S Fox, N S Cutler
1Departments of Genetics, Medicine, Microbiology, Pharmacology and Cancer Biology, and The Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA.
Abstract:
Calcineurin is the conserved target of the immunosuppressants cyclosporin A and FK506. Using the yeast two-hybrid system, we identified a novel calcineurin binding protein, CBP1, from the pathogenic fungus Cryptococcus neoformans. We show that CBP1 binds to calcineurin in vitro and in vivo, and FKBP12-FK506 inhibits CBP1 binding to calcineurin. Cryptococcus neoformans cbp1 mutant strains exhibit modest defects in growth under stress conditions and virulence, similar to but less severe than the phenotypes of calcineurin mutants. Saccharomyces cerevisiae mutants lacking the CBP1 homolog RCN1 are, like calcineurin mutants, sensitive to lithium cation stress. CBP1 shares a central peptide sequence motif, SPPxSPP, with related proteins in S.CEREVISIAE:, Schizosaccharomyces pombe, Drosophila melanogaster, Caenorhabditis elegans and humans, and peptides containing this motif altered calcineurin activity in vitro. Interestingly, the human CBP1 homolog DSCR1 is encoded by the Down's syndrome candidate region interval on chromosome 21, is highly expressed in the heart and central nervous system, and may play a role in calcineurin functions in heart development, neurite extension and memory.
Insights
Researchers discovered CBP1, a novel calcineurin binding protein in the fungus Cryptococcus neoformans. This protein impacts fungal growth and virulence, and its conserved motif suggests roles in human development and neurological functions.
Area of Science:
- Molecular Biology
- Mycology
- Genetics
Background:
- Calcineurin is a key target for immunosuppressants like cyclosporin A and FK506.
- Understanding calcineurin's regulatory network is crucial for its therapeutic targeting and understanding cellular processes.
Purpose of the Study:
- To identify and characterize novel calcineurin-interacting proteins.
- To investigate the function of a newly identified calcineurin binding protein (CBP1) in Cryptococcus neoformans.
Main Methods:
- Yeast two-hybrid system for protein-protein interaction screening.
- In vitro and in vivo binding assays to confirm calcineurin-CBP1 interaction.
- Construction and analysis of Cryptococcus neoformans cbp1 mutant strains.
Main Results:
- A novel calcineurin binding protein, CBP1, was identified in Cryptococcus neoformans.
- CBP1 directly binds to calcineurin, and this interaction is inhibited by FKBP12-FK506.
- cbp1 mutants showed modest defects in growth and virulence, phenotypes less severe than calcineurin mutants.
- Homologous proteins in yeast, flies, worms, and humans share a conserved SPPxSPP motif with CBP1, which affects calcineurin activity.
Conclusions:
- CBP1 is a functional calcineurin binding protein in Cryptococcus neoformans, contributing to stress response and virulence.
- The conserved CBP1 motif suggests a conserved role in calcineurin regulation across diverse organisms.
- The human homolog of CBP1, DSCR1, is implicated in Down syndrome and may influence calcineurin-mediated heart and brain development.