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Concerted dephosphorylation of the transcription factor NFAT1 induces a conformational switch that regulates

H Okamura1, J Aramburu, C García-Rodríguez

  • 1The Center for Blood Research and Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Molecular Cell
|October 13, 2000
PubMed

Insights

Dephosphorylation of NFAT1 (Nuclear Factor of Activated T-cells) by calcineurin is crucial for its transcriptional activity. This process unmasks key signals, promoting nuclear entry and gene regulation.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Transcription Factor Regulation

Background:

  • Nuclear Factor of Activated T-cells (NFAT) proteins are critical transcription factors regulated by calcium signaling.
  • These proteins are known to be heavily phosphorylated, influencing their localization and activity.

Purpose of the Study:

  • To elucidate the specific phosphorylation sites on NFAT1 and their role in regulating its function.
  • To understand the mechanism by which calcineurin-mediated dephosphorylation activates NFAT1.

Main Methods:

  • Mass spectrometry was employed to identify and quantify phosphorylation sites on NFAT1.
  • Functional assays were conducted to assess the impact of specific dephosphorylation events on NFAT1 localization and transcriptional activity.

Main Results:

  • NFAT1 is phosphorylated on fourteen conserved phosphoserine residues within its regulatory domain.
  • Dephosphorylation of thirteen of these residues upon stimulation is essential for masking the nuclear export signal (NES) and exposing the nuclear localization signal (NLS).
  • An additional inducible phosphorylation site in the transactivation domain also contributes to transcriptional activity.

Conclusions:

  • Dephosphorylation acts as a key switch, promoting NFAT1 activation by increasing the probability of an active conformation.
  • This mechanism, analogous to ion channel gating, highlights a paradigm for modification-induced functional changes in heavily phosphorylated proteins.
  • Understanding NFAT1 regulation provides insights into calcium-mediated gene expression and cellular responses.

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