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Cabin 1, a negative regulator for calcineurin signaling in T lymphocytes
1Center for Cancer Research and Deparmtent of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Abstract:
Calcineurin plays a pivotal role in the T cell receptor (TCR)-mediated signal transduction pathway and serves as a common target for the immunosuppressants FK506 and cyclosporin A. We report the identification of a novel endogenous calcineurin binding protein named Cabin 1 that inhibits calcineurin-mediated signal transduction. The interaction between Cabin 1 and calcineurin is dependent on PKC activation. Overexpression of Cabin 1 or its N-terminal truncation mutants inhibits the transcriptional activation of calcineurin-responsive elements in the interleukin-2 promoter and blocks dephosphorylation of NF-AT upon T cell activation. These results suggest a negative regulatory role for Cabin 1 in calcineurin signaling and provide a possible mechanism of feedback inhibition of TCR signaling through cross-talk between protein kinases and calcineurin.
Insights
A newly discovered protein, Cabin 1, acts as a negative regulator of calcineurin signaling. Cabin 1 inhibits T cell receptor (TCR) signaling by blocking calcineurin
Area of Science:
- Immunology
- Molecular Biology
- Cell Signaling
Background:
- Calcineurin is a crucial enzyme in T cell receptor (TCR)-mediated signal transduction.
- Calcineurin is a primary target for immunosuppressive drugs like FK506 and cyclosporin A.
- Understanding calcineurin regulation is vital for immune response modulation.
Purpose of the Study:
- To identify novel endogenous proteins that interact with and regulate calcineurin.
- To elucidate the role of Cabin 1 in calcineurin-mediated signaling pathways.
- To investigate the mechanism by which Cabin 1 affects T cell activation.
Main Methods:
- Identification of calcineurin binding proteins.
- Assays to determine the functional interaction between Cabin 1 and calcineurin.
- Overexpression studies of Cabin 1 and its mutants in T cells.
- Analysis of transcriptional activation of calcineurin-responsive elements and NF-AT dephosphorylation.
Main Results:
- A novel calcineurin binding protein, Cabin 1, was identified.
- Cabin 1 inhibits calcineurin activity, particularly upon protein kinase C (PKC) activation.
- Cabin 1 overexpression suppresses interleukin-2 promoter activity and NF-AT dephosphorylation in activated T cells.
Conclusions:
- Cabin 1 functions as a negative regulator of calcineurin signaling.
- Cabin 1 provides a feedback mechanism for inhibiting T cell receptor (TCR) signaling.
- Cross-talk between protein kinases and calcineurin, mediated by Cabin 1, is a key regulatory pathway.